Reprinted fromPlant Plant Protection Protection Quarterly Quarterly Vol.15(4) Vol.15(4) 2000 2000 131

Broom management

Proceedings of a workshop held at Ellerston and Moonan on 16–17 November 1998

This is part of a series of workshops sponsored by the Co-operative Research Centre for Weed Management Systems

Editors: A.W. Sheppard and J.R. Hosking Broom management

CRC eed management systems 132 Plant Protection Quarterly Vol.15(4) 2000

CRC Co-operative Research Centre for eed Weed Management Systems management Established and supported under the Australian Government’s systems Co-operative Research Centres Program

MISSION STATEMENT

The CRC is committed to increasing the sustainability of agriculture and protecting the natural environment by developing ecologically sound, cost effective weed manage- ment systems.

OBJECTIVES

• To reduce the impact of weeds on farm productivity and profitability by developing sustainable management programs that optimize the integration of chemical, bio- logical and ecological approaches for annual crop and pasture systems in the crop- ping zone of southern Australia.

• To develop practical integrated weed management systems that reduce weed infes- tation, protect the environment and enhance sustainability and productivity of Aus- tralian temperate perennial pasture ecosystems.

• To develop integrated strategies for the sustainable management of weeds invading natural ecosystems in temperate Australia, in order to maintain biological diversity of native flora and fauna and to prevent further degradation of natural habitats.

• To implement a suite of weed science and weed management education programs which, for the first time in Australia, offers a coordinated approach to educating undergraduates, postgraduates, professional land and natural resource managers, and the community.

• To interact with researchers and land managers to communicate the results of weed research and foster the adoption of resulting weed management strategies.

FOR FURTHER INFORMATION ABOUT THE CRC FOR WEED MANAGEMENT SYSTEMS

CRC for Weed Management Systems Waite Campus University of Adelaide PMB 1 Glen Osmond SA 5064

Phone: (08) 8303 6590 Fax: (08) 8303 7125 Email: [email protected] Plant Protection Quarterly Vol.15(4) 2000 133

Contents Broom management workshop

Broom (Cytisus scoparius (L.) Link) population management strategies Andy W. Sheppard, John R. Hosking and Andrew R. Leys 134 Raising awareness of the broom (Cytisus scoparius (L.) Link) problem on the Barrington Tops, New South Wales Bev Adams 139 An introduction to the biogeography and ecology of broom (Cytisus scoparius) in Australia J.M.B. Smith 140 Impacts of broom (Cytisus scoparius) in western North America Dennis L. Isaacson 145 Status of broom in New Zealand Simon Fowler and Pauline Syrett 148 Determinants of broom (Cytisus scoparius (L.) Link) abundance in Europe Quentin Paynter, Simon V. Fowler, Jane Memmott, Richard H. Shaw and Andy W. Sheppard 149 Factors affecting broom regeneration in Australia and their management implications Andy Sheppard, Peter Hodge and Quentin Paynter 156 Controlling broom (Cytisus scoparius) in pasture on the Barrington Tops – a graziers perspective A. Clark 161 Broom (Cytisus scoparius (L.) Link) competition and management in eucalypt tree farms C.D. Barnes and G.K. Holz 163 Controlling broom (Cytisus scoparius (L.) Link) in native forest ecosystems K. Carter and A. Signor 165 Herbicides for broom (Cytisus scoparius (L.) Link): testing alternatives to Grazon® Craig Hore 167 Controlling broom (Cytisus scoparius (L.) Link) in natural ecosystems in Barrington Tops National Park Mellesa Schroder and Chris Howard 169 Threats to the rare and threatened plant species of Barrington Tops Anne Heinrich and Bill Dowling 172 Brooms as part of the Australian nursery industry Ian Atkinson and Andy Sheppard 176 Broom (Cytisus scoparius (L.) Link) and fire: management implications Paul O. Downey 178 Cutting and mulching broom (Cytisus scoparius (L.) Link): a Tasmanian perspective Eddie Talbot 183 Broom workshop participants 186

Cover illustration of Cytisus scoparius (L.) Link, reproduced with the permission of the Royal Botanic Gardens, Sydney 134 Plant Protection Quarterly Vol.15(4) 2000 Broom management Proceedings of a workshop held at Ellerston and Moonan on 16–17 November 1998. Organized by Bev Adams and sponsored by the Cooperative Research Centre for Weed Management Systems and the Ellerston Pastoral Company.

Editors: A.W. Sheppard and J.R. Hosking

Broom (Cytisus scoparius (L.) Link) population Previous workshops on broom have been held in 1986 (at Barrington Tops) and management strategies in 1997 (at Tumut). The recommendations from the 1986 workshop (Atchison 1986) Andy W. SheppardA, John R. HoskingB and Andrew R. LeysC are outlined in Table 2, and many of them A CRC for Weed Management Systems, CSIRO Entomology, GPO Box 1700, have been implemented. Although no proceedings are available from the 1997 Canberra, Australian Capital Territory 2601, Australia. B workshop, one of its outcomes was that CRC for Weed Management Systems, NSW Agriculture, RMB 944, the Alpine Liaison Committee allocated Tamworth, New South Wales 2340, Australia. resources towards Victorian releases of C NSW National Parks and Wildlife Service, PO Box 1967, Hurstville, New broom biological control agents already South Wales 2220, Australia. released in New South Wales. On arrival at the workshop, partici- pants were allocated to one of six groups Summary relating to their area of expertise and pro- In November 1998 a broom management commercial forests and national parks. vided with a realistic broom management workshop was held with this title. The Also present were extension officers, and problem, a suggested budget and a task workshop aimed to review the status of local and regional council representatives list. The aim was to develop a manage- broom as a weed, from biogeographic, as well as representatives of community ment strategy for the given problem (see ecological and economic perspectives, and Landcare groups, and the nursery in- below), before the end of the workshop. assess the efficacy of available control dustry. The first day of the workshop consisted of options, and to start the development of The aim of the workshop was to review formal presentations to set the stage un- integrated strategies for broom control the status of broom as a weed, from der the following session headings: under a range of situations. Following biogeographic, ecological and economic • Broom problem in Australia and over- formal presentations a workshopping perspectives, assess the efficacy of avail- seas session was conducted aimed at develop- able control options, and to start the de- • Conflicts of interest ing best-bet management strategies for velopment of integrated strategies for • Why is broom a weed? broom in a range of typical situations broom control under a range of situations. • Practical management options where broom needs to be managed. This Expected outcomes from the perspective • Industries affected and current control was followed by a general discussion. of the participants at the commencement strategies The contexts of this workshop, the devel- of the workshop are listed in Table 1. • Evaluation oped ‘best bet’ strategies and outcomes of this workshop session are outlined in Table 1. Expected outcomes from this broom workshop as defined by the this paper (see Table 3). participants at the start of the workshop. Introduction Outcome Number. of respondents Broom (Cytisus scoparius (L.) Link) is an for each outcome exotic weed in five continents. Even 1. To meet and establish links with researchers and others doing broom within its native range, temperate Europe control 4 and eastern Asia, broom can reach an 2. To gain a broader perspective of the broom problem in Australia 3 abundance that requires management, 3. To identify knowledge gaps and prioritize areas for future research 3 particularly within forestry and grazing 4. Develop integrated strategies to contain and eradicate broom in natural systems (Hosking et al. 1998). In Novem- ecosystems 3 ber 1998, the Cooperative Research Centre 5. Refine control techniques and best practice guidelines 3 for Weed Management Systems and the 6. Become conversant with current best practice for broom control 1 Ellerston Pastoral Company sponsored a 7. Obtain information on the best native species to re-vegetate broom broom management workshop, to discuss infested areas 1 and develop integrated management 8. Learn of the impacts of broom on pastures 1 strategies for this weed. Thirty-two del- 9. Understand the realistic potential for effective biological control 1 egates attended the workshop, including 10. Coordinate biocontrol agent redistribution and monitoring of releases two from New Zealand and one from the and prioritize where/when further releases are to be made 1 USA. Two of the participants had been re- 11. Understand further biological control research needs and to prioritize sponsible for most of the research carried this research 1 out in the international biological control 12. Secure releases of biological control agents in north western Tasmania 1 program on broom in Europe since 1988. 13. To identify any scope for the use of native predators for biological control 1 Workshop participants had expertise in 14. Discuss need for research on genetic variation in broom 1 broom ecology, biological control, and 15. Develop collaborative research projects 1 management of broom on farms, in Plant Protection Quarterly Vol.15(4) 2000 135 Table 2. Outcomes of National Park Advisory Committee Broom workshop fire trialing both pre- and post-fire treat- held at the Barrington Tops in February 1986 (adapted from Atchison 1986). ments of slashing and herbicide. Funds would need to be ensured, however, for Required further research Status subsequent long-term biennial clean up 1. Develop greater contact and collaboration with the New Zealand and monitoring of cleared areas. broom biological control group and consider taking advantage of CSIRO’s infrastructure to commence an Australian biological control Catchment management program for broom Ongoing Broom is scattered along a 10 km stretch of a 2. Monitor the extent of broom infestations and distribution on the Tops Ongoing watercourse at the head end of a catchment in native bush within c. 20 m of the bank except 3. Encourage the collection of background information about broom and at the source of the infestation in an old home- the interactions with the rest of the landscape (particularly by Jeremy stead. A key risk is that the broom will spread Smith at University of New England, Armidale) Ongoing downstream into the whole river system, 4. Support research into the impact of broom on catchment hydrology Not done which includes a World Heritage Area 5. Support research into broom physiology and the impact of broom on (WHA). The aim of control includes a focus on modifying soil nitrogen levels Pilot study protecting as much as possible the native Required control measures riverine plant community, thereby mini- 6. Manage track access to prevent further spread of broom south into mizing risk of spread downstream. Given that the National Park Ongoing broom seed is known to be able to live for 7. Clean National Parks and Wildlife Service vehicles likely to have several years on the riverbed. Control budget become contaminated with broom seeds Ongoing c. $20 000 per annum. Management goal: (a) to map broom 8. Filter infected rivers and streams from the park with mesh that will presence and monitor spread, (b) to re- prevent seed spread Impractical move from, and control broom in, new 9. Control feral pigs Ongoing and peripheral locations and where over- Required extension hanging a water course, (c) contain and, 10. Increase public awareness of the threats of broom to the public good where possible, reduce existing estab- via media and mobile exhibitions Ongoing lished infestations around homestead and along access roads, (d) educate local landholders, local land management staff, The majority of these presentations has Management strategy: (a) Identify and machinery workers and the general pub- been edited (these proceedings). After map biodiversity ‘hot spots’ for local con- lic and encourage their assistance in the meeting socially in the evening to discuss trol of broom ($20 000 in the first year). (b) control program. the aim, the six workshop groups were al- Pull and spray broom at these sites in first Management strategy: (a) Survey the located a two-hour intensive session in the year and then monitor and control broom distribution and general age-class of morning of the second day to hammer out in these sites in subsequent years ($20 000 broom using both aerial and ground sur- their respective management strategies. A per annum). Management should include veying by professionals and volunteers. plenary discussion session took place for protecting/encouraging the existing na- (b) Identify stakeholders including the the last hour of the workshop. This discus- tive flora. (c) Map extent of broom distri- overcoming of ‘grey’ areas of accountabil- sion focused on relevant control options bution in the park and monitor spread ity between land management agencies, for different situations where broom is ($10 000 per annum). (d) Contain spread but also understand the State/Regional/ causing problems. Finally a field trip was of broom by strategically spraying Local planning contexts for weed manage- organized to allow participants to see first (Garlon® at 2 mL L-1) around the perimeter ment. (c) Define various management hand the extent and severity of broom in- of the infestation and satellite popula- zones such as the homestead, road corri- festations in the Barrington Tops area. tions, along roads and tracks, and at dors, river and WHA downstream. (d) A summary of specific weed problems campsites ($80 000 in the first year then Develop management prescriptions, cal- presented to each group is given below, $100 000 per annum). Delimit main infes- culate control costs and prioritize action together with the management goal, man- tations and control the main disturbance by zone: (i) WHA – high conservation as- agement strategies and evaluation proce- agent, i.e. by trapping pigs within these set risk – annual surveys at flowering time dures each group developed. This is fol- areas ($20 000 per annum). This would down the catchment to detect broom lowed by the outcomes of the final discus- limit the amount of broom regeneration. spread, removing all broom physically as sion. Old broom stands contain more native encountered (opportunistic control) – low species and are thus less dense and there- cost so highest priority. (ii) River – high A National Park fore less undesirable than young stands. conservation asset risk, high potential for A 10 000 ha broom infestation in a forested (e) Support biological control initiatives as ‘jump dispersal’, some risk of weed recur- National Park, with limited vehicle access, is the main control option for the main infes- rence – use ‘cut-and-paint’ method with a still spreading with small satellite infestations tations. suitable ratio of professionals and volun- building up from the edges. The infestation Evaluation procedure: (a) determine teers targeting reproductively mature supports a large feral pig population. The aim whether biodiversity at specific sites is specimens at flowering. Start with over- of control includes a focus on broom control maintained, (b) monitor broom spread in hanging plants working upstream from along roadsides and in public camping areas to the short and long-term through succes- limit of infestation before treating plants ensure some sensitivity towards how the pub- sive mapping and (c) assess success of pig up the bank. Mark significant treated in- lic perceives the park is managing its broom control through trapping frequency and festations (e.g. >4 m2) for future monitor- problem. Control budget $150 000 per annum. on-ground assessment of disturbance lev- ing of recruitment – high cost, but high Management goal: (a) Maintain the els. priority. (iii) Homestead – low conserva- biodiversity of invaded habitats with high The group considered that if further tion asset risk, high visibility – high vol- conservation value and (b) contain broom funds were available, these should be ume spraying, mulching and bulldozing spread and presence in areas used by the used to conduct studies within the main could be employed depending on re- public. infestations on the management value of sources, containing the edge of the 136 Plant Protection Quarterly Vol.15(4) 2000 infestation before working inwards. Con- (where visibility will be an issue) either by and a public responsibility of keeping the nox- tainment a high priority, complete re- mulching for medium sized stands ($1000 ious weed under control. Control budget lim- moval a low priority. (iv) Road corridors – ha-1 for 10 ha) or spot-spraying for isolated ited only by need to minimize control costs. if known flora suggests low conservation plants in patches less than c. 25 m2 Management goal: (a) containment of asset risk, survey and control broom us- ($10 000 per annum). (c) Set up a demon- broom within existing infested areas, (b) ing high volume spraying, marking sig- stration site at an aesthetically important elimination of broom from access roads nificant infestations for future monitoring point in the town, where several control and fire tracks, and (c) reduction in broom of recruitment. Containment a high prior- options are trialed e.g. mulching, slashing, impact on plantation production. ity, complete removal a low priority. (e) and oversowing with local perennial Management strategy: straightforward Causal factor remediation – encourage grasses and/or shrubs native to the region with regards to (a) and (b) using mapping, staff to remove broom seeds from machin- ($10 000 per annum). On private land chemical control and long-term monitor- ery and to control feral animals. (f) Educa- goats and possibly fire might also be in- ing to prevent broom spread and to elimi- tion and community awareness: (i) Ma- cluded in a trial. (d) Run a public aware- nate it along access roads and fire tracks. chinery operators need to understand the ness campaign. Educate the community To achieve (c), however, an adaptive man- threats of broom and the importance of with regard to the threat posed by broom. agement strategy should be adopted (Shea good machinery and excavation spoil hy- Capture community interest to change the et al. 1998), i.e. using the management giene. (ii) Land management agencies – way people perceive their town (e.g. con- process to improve the strategy itself by organize pre- and post-program imple- tract a landscape architect to plan and actively trying a range of management mentation meetings to follow State/Re- show how the town would look with the techniques and control levels to provide gional/Local plans. (iii) Homestead users weed replaced by local native species). internal checks on the process. and adjacent landowners – provide infor- Provide incentives to encourage local A research project to demonstrate the mation leaflets and advertising of pro- community/council cooperation, involve- impact of broom on forestry production gram implementation in local print media. ment, pride and ownership of the broom would be required before any further ac- (iv) WHA users – provide information control project by targeting local identities tion is taken (e.g. Barnes and Holz 2000). leaflets, weed identification guides, and and groups (e.g. Rotary, Returned Serv- Following this, novel control options to be articles in bush walking newsletters. (g) iceman’s League, etc.) and support other tried following harvest could be (a) Revegetation may have a role to play in communal activities that make use of the woodchop and roll timber waste and re- the Homestead area. land ($20 000 per annum). distribute rather than using windrows, (b) Evaluation procedure: (a) use succes- Evaluation procedure: (a) determine prepare ground for replanting soon after sive mapping to monitor short and long- the amounts of broom controlled by each harvest to allow broom to start to regener- term spread of broom downstream and method and carefully map and record ate prior to planting, (c) regenerating along access roads, (b) monitor controlled control efforts, particularly along roads broom is then sprayed with the highest and marked infestations for broom regen- and access tracks, also monitor any fur- recommended rates of glyphosate (e.g. eration and treat as necessary, (c) assess ther weed spread and (b) assess achieve- 1350 g a.i. ha-1) and the penetrant Pulse® the recovery of native riparian vegetation, ments against milestones set for gaining immediately prior to planting (e.g. Hore (d) quantify the area of broom controlled community involvement (e.g. attendance 2000). For existing broom infestations in in relation to area mapped. at display days, number of local people young plantings control options include: signing up and showing up, level of vol- (a) slashing broom between rows, (b) Infested township untary participation), and for passing on cleaning up inter-row areas with shielded Broom is infesting 1000 ha within and sur- the management of the project to a locally (to protect trees) applications of gly- rounding a township in a high-rainfall zone. run committee based on the outcomes of phosate, and (c) applying urea-based fer- The infestation covers both private and public the demonstration trial. tilizer (e.g. 200 kg nitrogen ha-1) to the land including a golf course, but generally oc- A significant budget would need to be young trees. (d) biological control, par- curs over previously managed grassland of in- maintained for at least five to ten years to ticularly using shoot feeders, may also troduced species, i.e. the underlying flora is of ensure that public involvement becomes help depress the growth rate and height of little conservation interest. Vehicle access is self-perpetuating. competing broom within the plantation, good and the area is not used for grazing. The thereby reducing its impact. infested area has large, medium and small Forestry Evaluation procedure: (a) monitoring patches of broom in a mixture of growth stages Broom infests several multiple hectare blocks the success of the containment campaign (seedlings, immature plants and mature of plantation trees. The plantations have a fell- outside plantations and (b) conduct an plants). This infestation is integrally associ- ing/replanting cycle of about 20 years at the economic analysis for each of the combi- ated with village activities with potentially end of which the whole block is disturbed. Dur- nations of management options trialed. many willing helpers to assist with control. ing this process windrows of tree stumps are The group suggested that one way to The aim of control includes improving the formed at seven row intervals in the plantation reduce the pressure of broom on future natural setting of the village and gaining a col- where broom may persist through most of the operations might be to set up a long rota- lective responsibility by the community to cycle. Broom is a problem in the replanting tion forestry trial (e.g. 40 years) aimed at remove and control the broom. Control budget phase, growing up quickly from seed and sawlog (i.e. plank) production rather than c. $50 000 per annum. smothering planted saplings or reducing pro- woodchips. Thinning the trees as part of Management goal: (a) prevent spread, ductivity by slowing growth of the young the management program may provide (b) improve the aesthetic value of the town plantation. In the last few years before planta- temporary openings in the canopy that with respect to the weed, (c) transfer own- tion harvesting, the broom itself is shaded out would force broom to germinate, before ership of the management program to the within the stand, but it has laid down a large the trees shade it out as they continue to local community and d) reduce the seedbank. Vehicle access is good and aerial mature. A long-term economic analysis in amount of broom in the long-term to treatment is economic. The infested areas are relation to current practice must also be an maintain local enthusiasm/ involvement of similar size, but forestry blocks in between important component of such a trial. in the management process. them are susceptible to invasion. The aim of Management strategy: (a) Map the in- control includes limiting economic losses to Cattle farm fested areas. (b) Treat outlier infestations the forestry industry, by limiting risk of spread Broom infests a property of several hundred to prevent spread, especially along roads of existing infestations into adjacent blocks hectares, only 20% of the land has no history Plant Protection Quarterly Vol.15(4) 2000 137 of broom. Some areas have had to be abandoned start-up costs such as for the goat demon- To date, the biological control program to broom due to poor access and low productiv- stration paddock and initial fence-line and in Australia has resulted in the release and ity of the pasture or along water courses, most track spraying would decline with time, establishment of three biological control of the infested productive areas have a broom continued expenditure would be required agents. Two further agents are in quaran- seedbank that keeps sending up young broom for spot-spraying, setting up wind breaks, tine and two more are still under investi- plants every year following attempts to control mulching, vertebrate pest control, and the gation in the native range. The first agent them. Broom is all down the valley so broom cattle fencing to divide the property into to be released in Australia, the twig min- seeds from the property are not likely to infest 20 ha paddocks. This last item might be ing moth, was released in 1993 (Syrett et previously uninfested areas. Only cattle are optional depending on variation in funds al. 1999). None of the agents are yet in run on the property, but there are also rabbits, between years. large enough numbers to be causing much kangaroos and wombats. The local council is damage in Australia. While this is disap- threatening to impose a fine if broom is not Threat to rare plant pointing, as each insect species has only controlled on the property. Vehicle access is At present, a rare orchid is only known to grow one generation a year, it is not unexpected. good to most of the property. The aim of con- in a broom-infested area of a National Park. The likely long-term damage caused by trol includes limiting loss of pasture to broom, The above ground parts of the plant are annual three of these potential agents in New pacifying neighbouring landholders, and con- and leaves and flowers are present in January Zealand and Oregon is high (S. Fowler vincing the council that you are conducting and February. Almost nothing else is known and D. Isaacson personal communica- control as efficiently as your budget allows. A about the biology of the plant. Part of the tion), although for some species it may typical annual budget for broom control would known orchid population is now under the take anything from 5 to 30 years to have a be c. $20 000, and would be very variable be- edge of the broom infestation. The location of significant impact. Nonetheless, the evi- tween years. the plant is not to be made public because of the dence to date does not support any idea Management goal: (a) to contain the ex- risk of orchid enthusiasts collecting known that an effective suite of agents has al- isting infestations within the first five plants. Control budget up to $15 000 per an- ready been introduced anywhere in the years, and (b) start reducing the size of the num. world to combat broom. For this reason infested area between year five and ten. Management goal: (a) protect the exist- the collaboration between Australia, New Management strategy: To satisfy neigh- ing threatened plant population by imme- Zealand and the Oregon Department of bours and local council in year one (a) diately controlling the invading broom in- Agriculture continues to support screen- spray fence lines and tracks using Grazon festation in a manner posing minimal risk ing and evaluation of new agents. The 1.7 L per 100 L ($4000), and (b) set up a to the threatened plant and (b) survey for most promising of these are currently a small fenced demonstration area involv- other populations of the threatened plant gall mite (Aceria genistae Nalepa), which ing a herd of 50–60 dairy goats ($3000 in similar habitats while starting ecologi- can kill plants and greatly reduces the goats, $6000 electric fencing), then (c) cal studies to better understand the plant. growth rate of the weed, and the gall fly carry out wombat and rabbit control Management strategy: (a) immediate (Hexomyza sarothamni (Hendel)), which is ($800). In years two to five: (d) continue to broom control to 10 m beyond the edge of known to be extremely specific and, with- spray fence lines and spot-spray flower- the threatened plant population irrespec- out a large complement of parasites, may ing broom every two years ($4000), (e) tive of broom stand age, this control restrict broom growth. fence to restrict cattle movement and pre- would consist of cutting broom and treat- New funding sources are required, vent seed distribution as budget allows, ing stumps with glyphosate to prevent however, as the core sponsors over the last dividing the property progressively into resprouting (c. $1000 per annum) and (b) nine years (NSW National Parks and 20 ha paddocks (c. $10 000 in a good year), $9000 would be allocated to surveys of the Wildlife Service, Ellerston Pastoral Com- (f) over-sow low to medium infestations threatened plant and studies on its ecol- pany and State Forests of NSW) will not with appropriate perennial grasses for the ogy, using contracted researchers, stu- be able to maintain the same level of sup- region and add organic fertilizer e.g. proc- dents or local enthusiasts. port for the program. A number of other essed sewage or ash ($200), (g) build Evaluation procedure: Annual moni- organizations represented at the work- windbreaks of trees (e.g. pine) on wind- toring of the size of the threatened plant shop expressed interest in contributing to ward fence-line of each goat paddock be- population. the biological control program. A key out- tween goat fence on inside and cattle fence Additional actions included: (a) con- come of the workshop was the recommen- on outside ($1500 per annum over four tribute to feral pig control within the dation that the future management of the years), (h) mulch around previously threatened habitat, (b) study the role of broom biological control program moves sprayed fence lines ($1500), (i) invite fire on the ecology of the threatened plant from being NSW-based to a National pro- Landcare and other interested community (if possible without further threatening gram managed by the CRC for Weed Man- groups in years 4 or 5 to learn about goat remaining populations), and (c) consider agement Systems. use. the likely horticultural value of the threat- For national park and state forest areas Evaluation procedure: Estimate the ened plant as a way of sponsoring man- on the Barrington Tops plateau, funds are area of broom infestation that has been re- agement efforts. Control budget required still needed for chemical control of broom turned to production each year in relation was considered to be c. $10 000 in the first in priority areas: roads and access tracks, to the total area infested each year. This year, with reduced amounts in subse- high visitation areas, and threatened spe- should directly involve local council rep- quent years when the nearby broom infes- cies habitats. Such a management ap- resentatives to obtain an independent as- tation has been removed and the surveys proach is expensive and is not sustainable sessment of success of the management completed. in the long-term, but essential to contain strategy and alleviate their concerns. broom infestations while biological con- Other control strategies could include General discussion trol is given a chance to work. flaming large broom plants to improve ac- Biological control was the first focus of ex- There are more options for broom con- cessibility to goats. Stocking rates should tensive discussion. It is still the only op- trol on-farm. Discussion revisited infor- be carefully monitored to prevent over- tion for the bulk of large infestations in mation presented in the talks pointing to- grazing as this will allow broom to regen- Australia – any other method was prohibi- wards the benefit of fencing broom areas erate in cleared paddocks. The estimated tively expensive – despite a risk that bio- into small paddocks and grazing these ar- required budget in the first year was logical control will not work and a long eas with Boer and milking goats. These c. $20 000 for a 200 ha property. While time frame for implementation. goats have been domesticated for many 138 Plant Protection Quarterly Vol.15(4) 2000 years and have shorter legs than feral or Table 3. Outcomes and recommendations from the workshop. Angora goats. As such, they are more eas- Outcomes and recommendations ily contained and they browse broom and shrubs in preference to grasses and leg- 1. A series of ‘best bet’ management strategies were developed to manage broom in- umes. Similarly the benefits of mulching festations in 6 realistic situations where it causes problems in Australia: (a) a Na- broom and using the mulch to delay re- tional Park, (b) in a catchment, (c) an infested township, (d) in commercial forestry, generation were also discussed (Talbot (e) on a cattle farm, (f) as a threat to rare plants (see text for details). 2000), especially if combined with over- 2. It was recommended that efforts to complete a biological control program be con- sowing of perennial grasses, although the tinued with a shift in funding and priorities from a state-based to a National pro- cost of mulching at c. $1000 ha-1 was too gram under the auspices of a national body e.g. the CRC for Weed Management high for most agricultural situations. Systems, which includes all the state and federal research organizations involved in Use of fire to control broom was also broom biological control research and extension work. discussed. It appeared that more research 3. Further research was required for the development of situation-focused broom was needed before this became a recom- management strategies involving existing knowledge on the effectiveness of herbi- mended management tool. A concern cides, mechanical removal, fire, goats and revegetation. with the use of fire was the observation 4. Arranging field days to demonstrate the effectiveness of long-term integrated strat- that rate of linear spread from an existing egies over short term, quick-fix strategies to educate local authorities in the need for infestation can double following fire (P. long-term management practices. Assistance from these authorities and an under- Downey personal communication). In standing of what can be achieved on individual properties would also aid long- farming situations it has a use to remove term control. the bulk of the broom and encourage ger- mination of broom seed prior to use of chemicals or goats. Discussions on chemi- workshop also provided contacts for fu- eds A.W. Sheppard and J.R. Hosking. cal control supported information from ture exchange of information on control Plant Protection Quarterly 15, 167-8. the presentations that this is effective in techniques. The outcomes of this work- Hosking, J.R., Smith, J.M.B. and Sheppard, the short term, but remains expensive and shop are summarized in Table 3. The pro- A.W. (1998). Cytisus scoparius (L.) Link needs to be followed up for many years ceedings provides a permanent record of ssp. scoparius. In ‘The biology of Aus- until the seedbank has been depleted. No- most of these discussions. tralian weeds’ Volume 2, eds F.D. body treating areas where plants had Panetta, R.H.Groves and R.C.H. Shep- seeded for a number of years had man- Acknowledgments herd, pp. 77-88. (R.G. and F.J. Richard- aged to reach the stage where seed no We would like to thank the workshop par- son, Melbourne). longer germinated. This was despite con- ticipants for their valuable contribution in Shea, K., Amarasekare, P., Mangel, M, trol being carried out continuously for the discussion sessions summarized in the Moore, J., Murdoch, W.W., Noonburg, over 20 years or more (Smith 2000). There proceedings. Bev Adams is to be thanked E., Parma, A., Pascual, M.A., Possing- are also significant risks of herbicide dam- for suggesting and then organizing the ham, H.P., Wilcox, W. and Yu, D. age to non-target species growing venue and accommodation. Tony Clark of (1998). Management of populations in amongst broom. Such species need to be Ellerston Pastoral Company kindly pro- conservation, harvesting and control. encouraged as replacement vegetation. vided the venue and he and his staff pro- Trends in Ecology and Evolution 13, A major concern with landholders was vided conference facilities and lunch for 371-5. that broom control on private properties participants at ‘Ellerston’. Richard Groves Smith, J.M.B. (2000). An introduction to was required by law and imposed by local and Sharon Corey for critical comments the biogeography and ecology of councils. The councils, however, still ex- on this manuscript. broom (Cytisus scoparius) in Australia. pect control measures applied by land- Proceedings of the broom symposium holders to be immediate, thus favouring References held at Ellerston and Moonan, 16–17 short-term effective, but long-term ineffec- Atchison, C.J. (1986). Broom workshop November 1998, eds A.W. Sheppard tive control options such as greater use of proceedings. Barrington Tops State and J.R. Hosking. Plant Protection Quar- herbicides. The risk of prosecution is driv- Forest and National Park, 22–23 Febru- terly 15, 140-4. ing this. There was a perceived need by ary 1986. Unpublished report. New Syrett, P., Fowler, S.V., Coombs, E.M., many present to educate local authorities South Wales National Parks and Wild- Hosking, J.R., Markin, G.P., Paynter, in the need for long-term management life Service. Q.E., and Sheppard, A.W. (1999). The practices. Assistance from these authori- Barnes, C.D. and Holz, G.K. (2000). Broom potential for biological control of ties and an understanding of what can be (Cytisus scoparius (L.) Link) competition Scotch broom (Cytisus scoparius (L.) achieved on individual properties would and management in eucalypt tree Link) and related weedy species. also aid long-term control. Arranging farms. Proceedings of the broom sym- Biocontrol News and Information 20, field days to demonstrate the effectiveness posium held at Ellerston and Moonan, 17-34. of long-term integrated strategies over 16–17 November 1998, eds A.W. Talbot E. (2000). Cutting and mulching short term, quick-fix strategies is a per- Sheppard and J.R. Hosking. Plant Pro- broom (Cytisus scoparius (L.) Link): a ceived need in the farming community tection Quarterly 15, 163-5. Tasmanian perspective. Proceedings of and is outlined as a recommendation of Hore C. (2000). Herbicides for broom the broom symposium held at Ellerston this workshop. (Cytisus scoparius (L.) Link): testing al- and Moonan, 16–17 November 1998, The workshop provided participants ternatives to Grazon®. Proceedings of eds A.W. Sheppard and J.R. Hosking. with information about methods that the broom symposium held at Ellerston Plant Protection Quarterly 15, 183-5. others had used to manage broom. The and Moonan, 16–17 November 1998, Plant Protection Quarterly Vol.15(4) 2000 139 • Hunter Pastoral Company (HPC) Tony Clark Raising awareness of the broom (Cytisus scoparius • Dungog Shire Council (L.) Link) problem on the Barrington Tops, Eric Pasenow, Des Hopson • Gloucester Shire Council New South Wales Bruce Redman • Gloucester Pasture Protection Board Bev Adams, PO Box 189, Scone, New South Wales 2337, Australia. Bill Carter • NSW Department of Agriculture (Gloucester) John Britton Summary • NSW Forestry Department (Glouces- Awareness of broom as a problem on the included in the NPWS estimates to Treas- ter) Tony Yates, John Freeman Barrington Tops increased following ac- ury. The Regional Director of NPWS then • NSW Soil Conservation Service tion of the Barrington Tops Advisory reintroduced the broom item during the Mike Fletcher Committee and the Barrington Tops allocation of Capital Works Grants and • Hunter Valley Conservation Trust Broom Council. This paper describes hoped for Ministerial approval. That Ian Furner how publicity and public pressure gen- $10 000 had already been put up as collat- • Hunter District Water Board erated by these groups led to the com- eral for a Commonwealth Employment Col McKenzie mencement of a biological control pro- Program grant and as this was a four to •NPWS Carl Atchinson, gram for broom and illustrates how sup- one allocation it was well worth the gam- John Trudgeon, Peter van Herk port can be generated for the manage- ble. The NPWS would either have $50 000, • Flick and Company Peter Edlick ment of environmental weeds. or nothing, to spend on broom control. At Those elected to form the executive were this time control measures were hit and Tony Clark as chairman, Carl Atchinson Introduction mainly miss. Fortunately the money came as deputy-chairman/secretary and Tony When the Barrington Tops National Park through that year. Yates as publicity officer. in New South Wales (NSW) was estab- By 1985 the Barrington Tops Advisory The committee decided that the func- lished in 1969 there were many hectares of Committee decided that the broom prob- tions of the Broom Council were to: broom, Cytisus scoparius (L.) Link, estab- lem was becoming serious on the plateau (a) act as a forum for the co-ordination of lished within its boundaries. The New and more reports were coming in of control activities, information and re- South Wales National Parks and Wildlife broom colonizing waterways leading off search relating to broom, Service (NPWS) surveyed the extent of the the plateau. These plants at lower altitude (b)foster public awareness of broom and problem and sought help from the New appeared to be able to set viable seed. The to build public support for its long term South Wales Department of Agriculture Committee suggested to NPWS that some control, and and chemical companies. For the next ten of the broom funding be diverted to hold- (c) work towards this long term control years there followed a period of trial and ing a Broom Workshop to which we through biological agents. error. However in 1980 and 1981 the use would invite as many experienced people In general business, the three organiza- of 2,4,5-T (active ingredient 2,4,5- as we could from the academic world, tions represented by the executive (HPC, trichlorophenoxy acetic acid) to spray neighbouring landholders and local weed NPWS and NSW Forestry Department) broom was suspended because of high control bodies. On 22–23 February 1986, discussed their recent commitment to the levels of 2,4,5-T in urine of park workers some 27 people came together to camp at destruction of broom, and a round figure and damage to native plants caused by the Little Murray and put their collective of $450 000 was estimated as the overall spray. The broom control program had al- thoughts forward. To those people we are cost. All agreed that the present methods ways been limited by the season and the all indebted. of control were both costly and inad- weather. The Forestry Commission also equate. had a major broom problem and used The Broom Council Garlon® (active ingredient triclopyr) on From that workshop the Committee de- Biological control areas close to water and walking trails and cided that: (a) there be a regional body The Barrington Tops Advisory Committee 2,4,5-T elsewhere. The Forestry Commis- formed called The Broom Council, (b) the determined that CSIRO research capacity sion also tried slash, burn and spray but Council would restrict its charter to the was needed, however, the thrust of CSIRO the regrowth was considerable. study of broom, (c) membership of the research was towards weeds of economic Council would include one person from significance, particularly pasture weeds, Barrington Tops Advisory each of the organizations initially invited whereas the invasion of broom was Committee to the Broom Workshop, with the power largely of environmental concern. How- The Barrington Tops Advisory Committee to co-opt extra relevant people (d) the ever, if funding was available the research for the national park was formed in about Council be an autonomous advisory and might become a higher priority. 1972. Advisory committees, which ini- coordinating body, however each member A motion was carried that the Council tially comprised of community repre- organization must retain responsibility for write to the Chairman of CSIRO, Neville sentatives, are appointed by the New broom control on its own lands, and (e) Wran, asking him to review CSIRO Plant South Wales government through the the Council would work towards long Industry work on environmental weeds Minister for Planning and the Environ- term biological control of broom. (by Dr. R. Groves) and requesting that ment. These Committees advise the Min- With NPWS agreement the first meet- CSIRO reconsider biological control re- ister via the departmental head who runs ing of the Broom Council was held at search of broom. The Council also re- the NPWS. Gloucester on the 24 March 1987, and the quested that the executive ascertain the By November 1983 the Barrington Tops following attended: costs of producing a single page informa- Advisory Committee was being told that • Barrington Tops Advisory Committee tion leaflet, in colour, which could be cir- funding for the broom program is ‘some- Bev Adams, Margaret Mason culated to relevant organizations, e.g. thing of a lucky dip’ and $10 000 was put • Scone Shire Council Doug Collison 4WD Clubs, National Parks Association up in the budget and for the first time in • Upper Hunter Pasture Protection and Shires. The Forestry Department sub- eight years this was refused and not Board Ken England sequently published such a sheet. The 140 Plant Protection Quarterly Vol.15(4) 2000 Council met every three months, collected Member for Scone, Colin Fischer, went on The Broom Council told the Ministers data on the broom distribution and con- radio and issued a press statement and that the Council’s estimated cost of estab- tinued a campaign to foster public aware- also wrote to Mr. Wran commending him lishing a broom biological control pro- ness. for his ‘genuine attempt to observe at first gram would be approximately $78 000 in Then came a stroke of luck! The Chair- hand this pernicious and insidious nox- year 1, $174 000 in year 2 and $141 000 in man of CSIRO, Neville Wran, was to be ious plant’. The Broom Council had now year 3 and subsequent years. CSIRO and guest speaker at a dinner of my old school, achieved aims (a) and (b) and set about HPC had committed themselves and it Fort Street, at the beginning of October gaining aim (c), a program for biological was hoped the NSW government would 1987. This gave me an opportunity for control, funded by government depart- do so as well. By 19 October 1988 there some personal contact with Mr. Wran ments and the HPC. was a joint submission from the Ministers placing the case for research factually be- After a change of government in the for Agriculture and Rural Affairs, the En- fore him. During this discussion it was NSW State election in 1988, the Broom vironment, and Natural Resources for a suggested that Mr. Wran might contact Council invited the Minister for Agricul- special allocation to partially fund a re- HPC and a helicopter trip was arranged ture and Rural Affairs (the Honourable search project by NSW Agriculture and as the best way to see the invasion of the Ian Armstrong), the Minister for the Envi- CSIRO to develop a broom biological con- weed was from the air. As a result Mr. ronment (the Honourable T. Moore) and trol program. Accordingly it was recom- Wran inspected the area in November the Minister for Natural Resources (the mended that special allocations be made 1987 when broom flowers were at their Honourable Ian Causley) to come to see over the next three financial years to meet best. for themselves the current and potential two-thirds of the estimated costs of the re- Then followed publicity of a sort the broom problem on the Barrington Tops. search program. This amounted to $38 000 Broom Council could not generate. Local members were aware that repre- in 1988/89, $125 700 in 1989/90 and Deputy Leader of the National Party in the sentatives from the Broom Council had at- $108 500 in 1991/92. Federal Parliament, Mr. Bruce Lloyd, ac- tended National Party Meetings in their The Broom Council had now com- cused Mr. Kerry Packer (Proprietor of electorates and had promulgated the ne- pleted all three functions that it had set out HPC) and Mr. Wran of cronyism in ques- cessity for government action to be taken to achieve in its first two years. tion time in the Legislative Assembly. The immediately if the broom infestation was media ran the story for twenty-four hours to be contained in the future. Conclusion with the television and the papers concen- The three ministers and two local mem- The Barrington Tops Advisory Committee trating on the visit. Suddenly everyone bers, members of the Broom Council, the and the Barrington Tops Broom Council knew about and saw in flower broom on Advisory Committee, the NPWS, and the managed to raise awareness of broom as a the Barrington Tops. Immediate Forestry Department gathered at Polblue problem on the Barrington Tops through retractions were demanded and received, half way through 1988 and with the assist- publicity and public pressure. As a result so the media publicity continued for an- ance of two helicopters donated by HPC funds were committed in 1989 for a bio- other few days. flew on a surveillance tour of the area cov- logical control campaign. This paper de- The Shires of Scone and Gloucester ered by broom. All costs up to this point in scribes activities necessary to generate wrote to the Leader of the National Party, time had been borne by individual mem- State government support for projects Ian Sinclair, to acquaint him with details bers of the Broom Council or the two De- aimed at controlling invasion of key envi- of the Broom Council and its work. State partments, NPWS and Forestry. ronmental weeds in National Parks.

(L.) L.A.S.Johnson) and gorse (Ulex An introduction to the biogeography and ecology of europeus L.) (Hosking et al. 1998). Of these, broom is arguably the most serious in- broom (Cytisus scoparius) in Australia vader, being widespread in southeastern Australia in little-disturbed as well as in J.M.B. Smith, School of Human and Environmental Studies, University of pastoral and peri-urban environments. New England, Armidale, New South Wales 2351, Australia. Montpellier broom, though widespread, is predominantly an invader of relatively disturbed sites, and gorse is significant only within a more limited, southern Summary range. Broom (Cytisus scoparius (L.) Link), a become prostrate, with thinning eventu- Broom forms a novel, dense shrub layer shrub with several uses in its native Eu- ally leading to patchy regeneration. Ma- in grasslands and open forests, shading rope, was first introduced to Australia in jor disturbance results in massive regen- out understorey plants, affecting animal about 1800 and has now become widely eration. Broom may have substantial eco- distributions and populations, and having established at many places in moist, cool logical impacts upon regeneration of serious impacts on various human activi- temperate regions. Single populations overstorey trees, survival of understorey ties. Its canopy provides a foliage projec- are probably rather uniform, but there plants, and fauna. tive cover usually exceeding 50%, and in are genetic variations between popula- eucalypt woodland at Barrington Tops its tions reflecting multiple introductions. Introduction: broom in Australia above-ground biomass (of which 13–27% Herbivores, both native and released in a Broom (Cytisus scoparius (L.) Link) is a is in the form of green shoots) has been biocontrol program, have so far had little member of tribe Genisteae, family recorded at 0.26–2.63 kg m-2 (Hosking et impact. At Barrington Tops (New South Fabaceae, a group of shrubs predomi- al. 1998). Similar values of 1.6 and 2.1 kg Wales), the largest Australian infesta- nantly native to the Northern Hemi- m-2 have recently been reported in north- tion, undisturbed stands in eucalypt sphere. No members of this tribe occur west Tasmania (Barnes and Holz 2000), re- woodland expand at c. 0.5 m per year. naturally in Australia. However, several spectively in and between tree rows in Seed dispersal by animals, vehicles or species are naturalized here, those of young eucalypt plantations. other agents leads to establishment of greatest concern (so far) being broom, Although broom is still expanding its new, distant populations. Older plants Montpellier broom (Genista monspessulana range, population, and impact in Plant Protection Quarterly Vol.15(4) 2000 141 Australia, there is hope that its advance 1993), and in Oregon it was used to stabi- from the two sources differed slightly but will not be inexorable. It appears inevita- lize littoral dunes (Isaacson 2000). It has consistently in date of flowering, foliage ble that sooner or later native insects or also been widely employed as an orna- colour, and overall shrub shape. (The other organisms will adapt their behav- mental shrub. plants were destroyed after about ten iour or physiology to cope with the plant’s Broom foliage contains a variety of al- years, but not before leaving a large and chemical defences and take advantage of kaloids which have led to its having sev- troublesome seedbank). In Tasmania, the ecological opportunity offered by this eral medicinal uses (Waterhouse 1986, subalpine Victoria, the Blue Mountains novel, huge source of nutrition. Evolution- 1988), but which have also resulted in (New South Wales) and sporadically else- ary changes permitting herbivores and mild poisoning in grazing animals (Clark where, wild broom populations include pathogens to exploit a new food source 2000, Parsons and Cuthbertson 1992). individuals with red lateral petals instead have been noted in many other cases over Grey kangaroos and feral horses browse of having the more common all-yellow timespans of the order of a century or less the plant on Barrington Tops (New South flowers. (Thompson 1998). It is encouraging to Wales) and keep isolated plants well Despite such inter-regional variability, note that some native Lepidoptera already trimmed, although they soon move on to genetic variation within individual Aus- sporadically use broom as a larval food- other feed and have no controlling influ- tralian broom populations is likely to be plant, and that garden plants of Spanish ence on the plant where it is abundant. narrow due to their having very small broom, Spartium junceum L., are damaged Goats and to a lesser extent sheep browse founder populations (that at Barrington extensively by caterpillars of one species the plant more consistently and can be Tops, for example, thought to have been a (tree lucerne moth, Uresiphita ornitho- used for effective control in pastoral situa- single pot plant, later planted in a garden pteralis (Guenée), Common 1990), particu- tions (Clark 2000, Sheppard, Hosking and – Waterhouse 1986, 1988). This lack of lo- larly in the Guyra area where they can Leys 2000). cal variability presumably makes plants in only be kept alive by repeated use of in- Broom has probably been introduced any particular population relatively nar- secticide. repeatedly to Australia, although little is row in their potential ecological tolerance, It is hoped that such a process of bring- known of its early history here. The first but raises the possibility that cross-polli- ing broom into better ecological balance Australian reference to the species ap- nation with plants of other provenance within its invaded Australian range will pears to be in the form of a request for might have the effect of broadening such be accelerated using biocontrol, through seeds made by Governor P.G. King in tolerance. importation of European species pre- 1798, to be grown and used as a substitute Many garden hybrid brooms, which adapted to feeding on broom. Three in- for hops. Broom was apparently growing have a wide range of flower colours, pro- sects have already been released (Hosking luxuriantly in the colony only a few years duce relatively few seeds and are far less et al. 1998) but have yet to multiply and later (Parsons 1981). Subsequent introduc- invasive than the more vigorous pure have a significant impact. tions were made for the horticultural broom. However, they might have consid- trade, and these have included cultivars erable potential significance in that they Distribution and uses of broom most of which are hybrids with other spe- include genetic material from species with Broom’s native distribution extends from cies. Broom hybrids are still freely avail- more southern distributions in Europe, southern Scandinavia to the Azores, and able at plant nurseries in Australia, with having greater adaptation to warm, dry from Europe’s Atlantic coast to Hungary about 250 000 plants being sold annually conditions. Broom in Australia is appar- and Ukraine. It commonly grows at (Atkinson and Sheppard 2000). ently restricted by climatic factors, for ex- higher, cooler altitudes in the more south- The present range of wild broom in ample plants growing from seeds trans- erly parts of this range. Nevertheless, it Australia includes regions of moist, cool ported by rivers off Barrington Tops to straddles a wide spectrum of climatic con- temperate climate in eastern New South warmer sites at much lower altitudes are ditions, and no doubt has a correspond- Wales, Victoria, Tasmania, the Adelaide not vigorous, and so far appear to be re- ingly wide range of climatically adapted Hills area of South Australia and subur- stricted to moist, riverine sites. It is possi- ecotypes. It is not known precisely where ban Perth. Overall it infests more than ble that although the plant is now ecologi- Australian broom populations originated, 200 000 ha (Hosking et al. 1998) but this cally unsuited to the relatively warm, dry although Britain seems most likely for cul- represents only a small part of its poten- environments away from those riverine tural and communication reasons. Broom tial range. For example, in northern New sites, acquisition of genetic material by has also been introduced to and become South Wales there are many areas ecologi- cross-pollination with horticultural hy- naturalized in North America, New Zea- cally very similar to Barrington Tops, such brids in or near gardens might provide land, South Africa, Hawaii, Iran, Japan as the Walcha pastoral district, and Ben such ecological capacity. and India, and is a major pest species in Halls Gap, Mt. Kaputar and New England the first two of these places. National Parks, where broom has not been Range expansion In Britain the plant had many uses reported. Broom has been extending its Australian which would have led to a desire to grow range since introduction. At Barrington the plant in the new colonies. These in- Genetics of Australian broom Tops its initial introduction to the prop- cluded: source of fibre and dye; browse for The genetic variation between and within erty ‘Tomalla’ in the 1840s was followed sheep, goats and deer; a substitute for broom populations in Australia is unre- by spread to the forested plateau where it hops; as well as the manufacture of searched, but such an investigation would was becoming a concern by the early brooms as its name implies (Usher 1974). be worthwhile. Most Australian natural- 1960s, and it expanded rapidly after cattle Elsewhere in Europe its pickled buds pro- ized broom is clearly C. scoparius without removal in the late 1960s (Hosking et al. vided a substitute for capers, and its seeds hybrid introgression. Nevertheless, there 1998, Waterhouse 1986). Broom is pres- a substitute for coffee (Hedrick 1972). In is certainly some genetic variation be- ently spreading in the Bogong High Plains India, broom has been used as a nurse tween populations which probably re- of Victoria, where it was not conspicuous crop in plantations of Eucalyptus and Aca- flects separate introductions from Europe. until after removal of cattle in 1992 (Hore cia, providing protection from wind and For example, I raised broom plants from 2000), although there as well as in other frost, as well as perhaps enhancing the ni- seed collected at both Barrington Tops and places its expansion is now being curtailed trogenous content of soils (Chinnamani et at Ebor (New South Wales). Two indi- at least to some degree by herbicide appli- al. 1965). In Japan broom has been used for viduals from each place were grown to cations (Robertson et al. 1999). The appar- post-fire erosion prevention (Nemoto et al. maturity side by side in Armidale. Plants ent acceleration of its spread in Australia 142 Plant Protection Quarterly Vol.15(4) 2000 in recent decades is paralleled by its his- tory in New Zealand where most spread (which is continuing) has also occurred in the past thirty years (Fowler and Syrett 2000). It is convenient to consider range ex- pansion under two headings, stand ex- pansion and jump dispersal (Figure 1), al- though the two are not discrete processes except in scale. Stand expansion occurs as a population expands its contiguous area by an incremental process of repeated short-distance dispersal. Jump dispersal is accomplished when an individual (lead- ing to a population) becomes established at a distance from the parent population after a (relatively) long-distance dispersal event, with a gap of uncolonized space re- maining (at least temporarily) between the parent and daughter populations.

Stand expansion Most broom seeds are dormant at the time of their explosive release from the pods, which flings them up to 5 m. They may then be collected by ants attracted to an oily caruncle which acts as an elaiosome, and carried by them a further 1 m (Smith and Harlen 1991). That the great majority of seeds is dispersed initially within a few metres of parent plants is confirmed by Robertson et al. (1999) who have mapped seedlings only up to about 10 m from burned, mature broom stands on the Figure 1. Conceptual model of the processes of range expansion in an Bogong High Plains. Dispersal on this invading species such as broom. scale, together with growth and lean of shrubs within the stand, leads to stand ex- ‘Tomalla’. The second lies to the south- jump dispersal events. At Barrington Tops pansion into surrounding, previously west, on the mainly forested plateau and control efforts using herbicides and uncolonized habitat. including large parts of Stewarts Brook through pulling have focused on the Stand expansion is not rapid under State Forest and Barrington Tops National eradication of such outlying plants, espe- conditions of low disturbance. Four per- Park, almost certainly derived from the cially where they occur in places where manent plots have been monitored nearly first by dispersal of seeds internally or ex- their seeds might more readily find dis- annually for more than twelve years in ternally by cattle or horses. Other, more persal agents (e.g. at campsites and along eucalypt woodland near Polblue Swamp, recent long ‘jumps’, in this case probably roadsides). Barrington Tops (Downey and Smith, in through seeds adhering in mud to foot- press). At two of these plots, which ini- wear and logging equipment, or possibly Persistence tially straddled the edges of broom stands, by mammals, have been noted (and The process whereby broom regenerates stand expansion occurred at a rate of only daughter populations eliminated) else- and thereby persists at a site after initial about 0.5 m per year. Disturbance acceler- where in this region, at Gloucester Tops invasion is relevant to management, espe- ates the process by increasing rates of seed and Giro State Forest. cially in places of conservation signifi- germination and seedling establishment, At a local scale, jump dispersal com- cance where attempted control measures so that after fire, herbicide treatment or monly leads to establishment of individu- such as heavy grazing, herbicide, fire or physical disturbance, regrowing stands als tens or hundreds of metres from seed- other large disturbances are inappropriate may be both denser (Moodie 1985) and ing stands, due to occasional seed disper- or difficult to apply. Broom plants may larger (Robertson et al. 1999) than before sal by mammals (pigs and horses – Smith live up to at least 27 years at Barrington the disturbance. and Harlen 1991, sheep – Clark 2000, Tops (Downey and Smith, in press), and probably cattle and possibly macropods) all regeneration is by seed rather than by Jump dispersal ingesting seeds and passing them in vi- vegetative means. Initial broom colonization of Australia can able condition, in streams, or by humans be considered to be a human-mediated or their vehicles and equipment. Scattered Seed dynamics case of jump dispersal at the largest scale. broom shrubs in grassland areas at Broom seed production has been meas- The expansion of broom’s range to the Barrington Tops are thought to have been ured in New South Wales at 28–356 and Barrington Tops plateau provides an ex- mainly a result of dispersal by feral horses 107 seeds m-2 per year on broom plants ample on a regional scale: helicopter map- (Smith and Harlen 1991). below a eucalypt canopy at Barrington ping of broom in this area has shown that Populations derived from such isolated Tops and at Deua National Park respec- there are two discrete, large populations. broom plants may eventually coalesce tively, and at 8885 and 7700 seeds m-2 per The first is the original population in and with the original stand as both spread to- year away from overstorey trees at Deua near the pastoral area to the north, derived wards each other in a process of infilling. (Hosking et al. 1998) and Armidale (Smith by spread from the first planting at They can also be the sources for further and Harlen 1991) respectively. These Plant Protection Quarterly Vol.15(4) 2000 143 values are greatly in excess of the mini- isolated populations. There is an annual nearly continuous broom canopy (Smith mum necessary for stand replacement, program to locate and destroy regenerat- 1994a). Only when such gaps occupy at supported by the observation of abundant ing broom at known, marked sites in least half of the area, and significant sun- seedlings appearing within broom stands Kosciuszko National Park (L. Knutson light penetrates to the ground, do new every year. As a contrast, the relatively personal communication). If such meas- broom individuals become established common and widespread native ures are not maintained, regeneration is (Downey and Smith, in press). fabaceous shrub, sweet wattle, Acacia likely to lead within a few years to further It seems probable that in forested areas suaveolens (Smith) Willd. (which has simi- accessions to the soil seedbank. For exam- of the Barrington Tops plateau, without lar-sized, hard seeds, and also depends on ple, roadside broom plants were flower- intervention, eventually a stable, mixed- seedling establishment for its persistence) ing again in 1998 at Glencoe and Ebor in age broom population will develop. This was found by Auld and Myerscough northern New South Wales despite de- permanent broom layer in the vegetation (1986) to produce annually only about struction of plants at those sites about four (although less dense than first generation, four seeds per plant. This seems to cast years earlier. single-age broom stands, or stands result- doubt on whether curtailment of broom ing from major disturbances) will have seed production by biocontrol agents is Broom stand dynamics at far-reaching ecological consequences. likely to have any practical effect, other Barrington Tops These may include local extinction of rare than a possible reduction in the frequency Observations in permanent plots in herbaceous plants (Heinrich and Dowling of jump dispersal. broom-invaded eucalypt forest at Barring- 2000); thinning or elimination of the euca- The reservoir of dormant seeds accu- ton Tops over more than ten years lypt canopy by prevention of eucalypt re- mulating in the soil beneath and near (Downey and Smith, in press) indicate generation (Waterhouse 1986, 1988); inva- broom stands is undoubtedly the princi- that broom shading curbs regeneration by sion by rainforest plants into former euca- pal factor making broom control so intrac- broom itself (as well as by many members lypt woodland (Smith 1994a); multiplica- table. Broom plants are easy to kill with of the native flora) until the original plants tion of feral pigs with resultant physical herbicides, burning, slashing or pulling, progressively senesce and die to the point and biotic disturbance; increase in num- and resprout poorly from stumps. How- where their canopy is significantly bers of some native birds (Bell 1990); and ever, any disturbance which exposes sur- opened. Broom seedlings are observed invasion by alien birds (Smith 1994b). face soil to the temperature variations re- continually at earlier stages, but rarely In more open sites, it appears that while sulting from direct sunlight and nocturnal survive for more than a few weeks or some physical disturbance is necessary for radiative cooling leads to partial germina- months. The original broom plants, as establishment of new broom plants, small tion of the soil seedbank. If they are ad- they age, collapse from their previously natural disturbances (e.g. animal grazing, equately lit and do not experience erect form to become prostrate, with stems digging or trampling) are sufficient to al- drought, seedlings establish well, and a lying along the ground for more than five low range expansion to occur even in the broom thicket quickly returns to the site metres to terminate in green, fertile complete absence of human activities. usually at higher density than previously crowns some two metres in height. At More substantial disturbance leads to (Moodie 1985). This regrowth needs to be Barrington Tops their collapse is acceler- massive seedling establishment wherever killed within four years of the original dis- ated by falls of heavy, wet snow (Smith broom seeds are present, resulting in the turbance before it produces further seeds, 1994a). Over a period of about thirty years creation of dense new broom stands but even if this is achieved, seeds from the from initial invasion, the population com- (Moodie 1985) from germination of part of original seedbank will continue to germi- prises progressively fewer, larger and the large, long-lived soil seedbank (Mihe nate for many more years, requiring re- more prostrate individuals (Figure 2). The 1992, Smith and Harlen 1991) accumu- peated treatment. At a campsite near process of collapse results in crowns fall- lated beneath former stands. It has been Polblue Swamp, Barrington Tops, broom ing across each other, the lower of which suggested (P. Downey, personal commu- seedlings still appear twenty years after dies, forming gaps in the previously nication 1997, Robertson et al. 1999, the site was cleared of broom, even though no further plants have been allowed to 2 develop to maturity during that period. Basal area 1–9.9 cm Broom soil seedbanks in Australia have Basal area 10+ cm2 been measured at values ranging from 190 60 -2

to 50 000 seeds m , values comparable to 2 those found within the plant’s native range (Hosking et al. 1998). At Barrington Plot 1 Plot 4 Tops, Mihe (1992) found that up to 40% of seeds were in soil deeper than 5 cm. While 40 such seeds might be too deep for develop- ing seedlings to emerge above the soil sur- face, they are also less likely than shallowly buried seeds to have their ger- mination triggered by variations in tem- 20 perature or moisture. They might there- No. of stems per 25 m fore be expected to remain dormant for extended periods, perhaps until moved closer to the surface by digging animals or other agents, posing long-term difficulties for control operations. 10 20 30 With widening recognition of broom’s Age of broom stand (years) importance, and in order to curb its spread, control measures have been more Figure 2. Numbers of live broom plants in two size (basal area) categories in vigorously adopted in recent years, par- two 5 × 5 m permanent plots near Polblue Swamp, Barrington Tops, over ticularly herbicide application to small, periods of thirteen and twelve years respectively. 144 Plant Protection Quarterly Vol.15(4) 2000 Sheppard, Hodge and Paynter 2000) that A.W. Sheppard and J.R. Hosking. Plant southwest Japan, Proceedings of the fire might be employed to stimulate ger- Protection Quarterly 15, 178-83. 10th Australian Weeds Conference and mination to the extent that herbicidal or Downey, P.O. and Smith, J.M.B. (In press). 14th Asian Pacific Weed Science Con- other treatment of the dense regrowth Demography of the invasive shrub ference 1, 333-8 (Weed Society of might then lead to substantial control. Scotch broom (Cytisus scoparius) at Queensland, Brisbane). Downey (2000) has found up to 80% re- Barrington Tops, New South Wales: Parsons, W.T. (1981). The history of intro- duction in the soil seedbank of broom af- insights for management. Australian duced weeds. In ‘Plants and Man in ter fire. However, it has yet to be demon- Journal of Ecology. Australia’, eds D.J. and S.G.M. Carr, strated that this will lead to sufficient re- Fowler, S. and Syrett, P. (2000). Status of pp. 179-93. (Academic Press, Sydney). duction in subsequent broom regenera- broom in New Zealand. Proceedings of Parsons, W.T. and Cuthbertson, E.G. tion to be a useful control tool, and in any the broom symposium held at Ellerston (1992). ‘Noxious weeds of Australia’. case fire is not easy to use in many situa- and Moonan, 16–17 November 1998, (Inkata Press, Melbourne and Sydney). tions. eds A.W. Sheppard and J.R. Hosking. Robertson, D.C., Morgan, J.W. and White, Plant Protection Quarterly 15, 148. M., (1999). Use of fire to enhance con- References Hedrick, V.P. (ed.) (1972). ‘Sturtevant’s trol of English Broom (Cytisus scoparius) Atkinson, I. and Sheppard, A. (2000). edible plants of the World.’ (Dover invading a subalpine snowgum wood- Brooms as part of the Australian nurs- Publications, New York). land in Victoria. Plant Protection Quar- ery industry. Proceedings of the broom Heinrich, A. and. Dowling, B. (2000). terly 14, 51-6. symposium held at Ellerston and Threats to the rare and threatened plant Sheppard, A.W., Hodge P. and Paynter Q. Moonan, 16–17 November 1998, eds species of Barrington Tops. Proceed- (2000). Factors affecting broom regen- A.W. Sheppard and J.R. Hosking. Plant ings of the broom symposium held eration in Australia and their manage- Protection Quarterly 15, 176-8. at Ellerston and Moonan, 16–17 ment implications. Proceedings of the Auld, T.D. and Myerscough, P.J. (1986). November 1998, eds A.W. Sheppard broom symposium held at Ellerston Population dynamics of the shrub Aca- and J.R. Hosking. Plant Protection Quar- and Moonan, 16–17 November 1998, cia suaveolens (Sm.) Willd.: seed produc- terly 15, 172-6. eds A.W. Sheppard and J.R. Hosking. tion and predispersal seed predation. Hore, C. (2000). Herbicides for broom Plant Protection Quarterly 15, 156-61. Australian Journal of Ecology 11, 219-34. (Cytisus scoparius (L.) Link): testing al- Sheppard, A.W., Hosking J.R. and Leys, Barnes, C.D. and Holz, G.K. (2000). Broom ternatives to Grazon®. Proceedings of A.R. (2000). Broom (Cytisus scoparius (Cytisus scoparius (L.) Link) competition the broom symposium held at Ellerston (L.) Link) population management and management in eucalypt tree and Moonan, 16–17 November 1998, strategies. Proceedings of the broom farms. Proceedings of the broom sym- eds A.W. Sheppard and J.R. Hosking. symposium held at Ellerston and posium held at Ellerston and Moonan, Plant Protection Quarterly 15, 167-8. Moonan, 16–17 November 1998, eds 16–17 November 1998, eds A.W. Hosking, J.R., Smith, J.M.B. and Sheppard, A.W. Sheppard and J.R. Hosking. Plant Sheppard and J.R. Hosking. Plant Pro- A.W. (1998). Cytisus scoparius (L.) Link Protection Quarterly 15, 134-9. tection Quarterly 15, 163-5. ssp. scoparius. In ‘The biology of Aus- Smith, J.M.B. (1994a). The changing eco- Bell, S.A.J. (1990). Effects of the weed tralian weeds’, Volume 2, eds F.D. logical impact of broom (Cytisus scopar- Scotch broom on bird communities in Panetta, R.H. Groves and R.C.H. Shep- ius) at Barrington Tops, New South open forests on Barrington Tops. B.Sc. herd, pp. 77-88. (R.G. and F.J. Wales. Plant Protection Quarterly 9, 6-11. Hons Thesis, Dept. Geography, Univer- Richardson, Melbourne). Smith, J.M.B. (1994b). Blackbirds reach sity of Newcastle. Isaacson, D.L. (2000). Impacts of broom Barrington Tops. Australian Birdwatcher Chinnamani, S., Gupte, S.C., Rege, N.D. (Cytisus scoparius), in western North 15, 273-5. and Thomas, P.K. (1965). Afforestation America. Proceedings of the broom Smith, J.M.B. and Harlen, R.L. (1991). Pre- with broom as a nurse crop. Indian For- symposium held at Ellerston and liminary observations on the seed dy- ester 91, 573-6. Moonan, 16–17 November 1998, eds namics of broom (Cytisus scoparius) at Clark, A. (2000). Controlling broom A.W. Sheppard and J.R. Hosking. Plant Barrington Tops, New South Wales. (Cytisus scoparius) in pasture on the Protection Quarterly 15, 145-8. Plant Protection Quarterly 6, 73-8. Barrington Tops – a graziers perspec- Mihe, T. (1992). ‘The density and distribu- Usher, G. (1974). ‘A dictionary of plants tive. Proceedings of the broom sympo- tion with depth of the soil seed bank of used by Man’. (Constable, London). sium held at Ellerston and Moonan, 16– broom (Cytisus scoparius) on Barrington Thompson, J.N. (1998). Rapid evolution as 17 November 1998, eds A.W. Sheppard Tops NSW’. B.Nat.Res. Project Report, an ecological process. Trends in Ecology and J.R. Hosking. Plant Protection Quar- University of New England, Armidale. and Evolution 13, 329-32. terly 15, 161-2. Moodie, J.C. (1985). An evaluation of con- Waterhouse, B.M. (1986). ‘Cytisus scopar- Common, I.F.B. (1990). ‘Moths of Aus- trol techniques for broom (Cytisus sco- ius (Broom) on Barrington Tops.’ B.A. tralia’, p. 358. (Melbourne University parius) on Barrington Tops. B.Nat.Res. Hons. Thesis, University of New Eng- Press, Melbourne). Project Report, University of New Eng- land, Armidale. Downey, P. (2000). Broom (Cytisus scopar- land, Armidale. Waterhouse, B.M. (1988). Broom (Cytisus ius (L.) Link) and fire: management im- Nemoto, M., Nakagoshi N., Horie, H. and scoparius) at Barrington Tops, New plications. Proceedings of the broom Nishimura N. (1993). Allelopathic South Wales. Australian Geographical symposium held at Ellerston and potential of broom (Sarothamnus scopar- Studies 26, 239-48. Moonan, 16–17 November 1998, eds ius) dominating post-fire stands in Plant Protection Quarterly Vol.15(4) 2000 145 weed (Dorworth et al. 1996). It is listed on the All States’ Noxious Weed Seed List Impacts of broom (Cytisus scoparius) in western maintained by the United States Depart- North America ment of Agriculture (USDA) Agricultural Marketing Service’s Seed Regulatory and Testing Branch (Anon. 1998). It is re- Dennis L. Isaacson, Oregon Department of Agriculture, 635 Capitol Street garded as a common weed in Hawaii and NE, Salem, Oregon 97301, USA. Iran, and as a principle pest in New Zea- land (Holm et al. 1979) and as a noxious weed in parts of Australia (Parsons and Summary hundred kilometres, and eastward from Cuthbertson 1992). There are many economic and ecological Vancouver about 120 km, with scattered consequences of the success of the intro- occurrences in eastern British Columbia General comments on impacts of broom duced weed, broom (Cytisus scoparius), (Dorworth et al. 1996). There are different perspectives on im- in western North America. Results of a The first records of broom in Oregon pacts of broom in western United States. survey of landowners and managers in- are from the late 1880s, and broom has For example, the main concern of foresters volved in forest regeneration and with steadily increased its range since then to is broom’s interference with regeneration roadside vegetation management are the present (see Figure 1). The current ex- of Douglas fir (Pseudotsuga menziesii presented, and some ecological impacts tent of broom in western United States is (Mirb.) Franco) plantations; road mainte- are described and their extent is dis- illustrated in Figure 2. nance personnel are concerned with the cussed. While there are some positive influence of broom and other brushy spe- economic impacts, the negative effects of Status of broom as a pest cies on sight safety distance and erosion broom are considerable and conserva- In the western United States, broom is near roadsides; and natural area manag- tively amount to more than US $11 mil- now regarded as a pest and is listed on ers are concerned with broom’s interac- lion ($A16.5 million) in western North noxious weed lists for California, Wash- tion with both physical and biotic charac- America. Many of the ecological impacts ington and Oregon. It is also generally re- teristics of the landscape. In the forestry of broom invasion are not known, or are garded as a pest in British Columbia al- setting, actions are often taken which di- poorly understood, but its role in stabil- though it is not listed there as a noxious rectly target broom. In many settings izing dunes along the western coastline of North America is substantial. 25

Introduction Distribution of broom 20 ● Broom (Cytisus scoparius (L.) Link) has been introduced into and established in 15 Australia, eastern and western Canada, ● ● Chile, India, New Zealand, Japan, South ● Africa and eastern and western regions of ● 10 ● the United States (Holm et al. 1979, ● ● Hosking et al. 1996, Luken and Thieret No. of Counties ● 1997). Its native range extends from Swe- ● 5 ● den in the north to southern Spain and the ● ● Azores, and from Ireland in the west to ● west central Ukraine (Tutin et al. 1968). It ● is known in Canada from the provinces of 0 British Columbia, Nova Scotia and Prince 1880 1892 1916 1917 1920 1932 1936 1952 1953 1958 1966 1967 1981 1983 1995 Edward Island, and in the United States Year from the states of Alaska, California, Con- Figure 1. Extent of broom (Cytisus scoparius) in Oregon. necticut, Delaware, Georgia, Hawaii, Maryland, Maine, Montana, North Caro- 60 lina, New Jersey, New York, Ohio, Or- 55 egon, Pennsylvania, South Carolina, Ten- ● 50 ● nessee, Utah, Virginia, Washington and 45 West Virginia (Luken and Thieret 1997). 40 Its range in the western United States is ● expanding, and densities of broom within 35 ● ● its established range there are also increas- 30 ● ● ● ● ing. Formerly regarded as a species best 25 ● ● adapted to coastal climates, broom has es- ● ● 20 ● ● tablished in areas within the continental ● ● No. of Counties ● 15 ● climate of the Great Basin of the western ● ● ● United States, growing to maturity in five 10 ● ● ● 5 ● ● eastern Oregon counties, in eastern Wash- ● ● ● ● ington (Lantz 1996), and in Idaho 0 (Callihan and Miller 1994). Broom was in- 1880 1893 1916 1920 1925 1932 1946 1952 1958 1963 1966 1968 1972 1981 1987 1996 troduced into western Canada in 1850 Year (Pojar and MacKinnon 1994), and it now occurs on southern Vancouver Island, Figure 2. Extent of broom (Cytisus scoparius) in the Pacific Northwest of the north along the mainland coast several United States of America. 146 Plant Protection Quarterly Vol.15(4) 2000 along roads, broom is but one of the plants ment of native and desirable plant species. Private foresters reported manual and/or that cause problems with sight safety or This is particularly true in forest settings, chemical treatments on more than 2670 ha erosion, and there are fewer instances of where broom interferes with reforestation of broom annually. These foresters also actions being taken that directly target efforts (Balneaves 1992). Dense stands of reported annual treatments on 22 250 ha broom. In the case of landscape change, broom also cause safety problems. Broom for brush control where broom was a broom interacts with other species to alter often grows along roadways, and can component of the target vegetation, but successional change and physical features reach two to three metres or more in where it was not dominant. Annual treat- of the landscape. Evaluating impacts of height, and this can create sight-safety ment costs targeting broom averaged broom from such differing perspectives hazards, particularly at intersections, $US424 000 ($A636 000) over the previous presents a challenge; we would like to driveways and around bends. It is also a three years at $US158 ($A237) ha-1. have a common measure of utility that fire hazard (Goeden 1978), of concern in Manual costs for broom treatments were would neatly summarize the importance both forest and roadside settings, and, like more costly at $US238 ($A357) ha-1, but of broom, but we do not. gorse (Ulex europaeus L.), can be a fuel few areas were so treated. In this overview, I take two different source for quick-burning fires. BLM personnel reported broom as sig- approaches to evaluating broom’s impor- In 1998, Decker (1998) completed a sur- nificant or dominant on 49 000 ha in pub- tance. First, I outline some important eco- vey of foresters and road maintenance licly-held forest production. There were nomic impacts of broom in three different managers in an attempt to quantify some no chemical treatments on BLM lands, due areas; forestry, roadside treatments and broom impacts in forests and along to herbicide use restrictions, and one unit nursery production. Secondly, I describe roadsides in western Oregon. She sent initiated a five-year manual treatment broom’s role in one particular landscape surveys to 48 private industrial forestry program on 32 ha. Infestation and control setting, that of oceanside dunes, to show firms, 15 BLM forest management units, data for forestry settings are summarized the extent and complexity of changes and 60 private and public organizations in Table 1. broom may cause. with road maintenance responsibilities. Responses were returned from 32 of the 48 (b) Road maintenance. Private road man- Economic impacts of broom forestry firms, representing management agers maintaining 15 050 km of road re- There are two recent surveys of the eco- and/or ownership of 1.3 million ha, and ported broom on 805 km of their nomic impacts of broom. From one, I de- 12 of the 15 BLM units representing 0.5 roadsides. Of these, 355 km were seriously veloped several estimates that summarize: million ha of publicly held lands in forest affected by broom, and they expended (i) the extent of broom in western Oregon production. There were 42 road mainte- $US40 250 ($A60 375) annually for treat- on industrial forest lands and on federal nance responses, representing nearly ment. Non-federal public road managers forest lands administered by the United 32 350 km of roads. maintained 19 950 km of road, 3780 of States Department of the Interior’s Bureau which were reported with broom. Aver- of Land Management (BLM), (ii) the ex- (a) Forest regeneration. Broom was re- age costs for vegetation management on tent of broom infestations along western ported as a significant or dominant plant these roads were $US1163 ($A1745) km-1, Oregon public and private roads, (iii) on 46 000 ha of privately held forest land, but there were few treatments that tar- treatment costs in forest and roadside set- and broom was reported as present on geted only broom. BLM road managers tings. In the other, I assessed the benefits about 84% of units undergoing regenera- reported maintaining 13 440 km of roads, to the nursery industry in Oregon of tion. Broom was regarded as more diffi- 915 of which had broom as a significant or brooms. cult to control than other weedy species by dominant component, with treatment 84% of respondees, and only three costs of $US786 ($A1179) km-1. Infestation Economic costs of broom in forest respondees did not consider that broom and control data along roadsides are sum- regeneration and road maintenance increased yearly production and mainte- marized in Table 2. Dense stands of broom prevent establish- nance costs within their operations.

Table 1. Broom control in western Oregon forests (based on Decker 1998). Forest ownership Managed area Area requiring Area requiring 1997 treatment 1997 treatment (ha) and/or and/or costs area monitoring monitoring ($US) (ha) treatment (ha) treatment (%) Private industrial forestry firmsA 1 300 000 46 000 3.56 424 000 2 670D US Department of Interior, 500 000 49 000 8.13 8 000C 32CD Bureau of Land ManagementB A 32 responses from 48 surveys. B 12 responses from 15 surveys. C Not from Decker (1998). D Treatment specifically for broom, not general brush control.

Table 2. Broom control along western Oregon roadsides (based on Decker 1998). Road owners/managers Road maintained Infested with km broom Broom treatment Broom treatment costs (km) broom (km) (%) (km) ($US) Private industrial forestry firms 15 050 805 5.3 355 40 250C Non -federal public 19 950 3 780 19.0 –B US Department of Interior, 13 440 8 940A 66.7A 915 181 250C Bureau of Land Management A From % categories reported for 9 of 15 surveyed units, these figures contain a bias towards over-estimation. B No reports of treat- ments specifically for broom. C Treatments by forestry firms mainly chemical treatments; Bureau of Land Management treatments are manual/physical and often directed at maintaining right-of-way rather than of a specific target weed infestation. Plant Protection Quarterly Vol.15(4) 2000 147 Benefits of broom production to Oregon number and diversity of small woodlot 1936, and both the rocky headlands and nurseries owners would complicate the survey be- the sandy areas represented challenges to Broom is valued for its showy flowers, for yond her intended scope. While the dis- the completion of this road, US Highway its capacity to serve as a visual screen, and persion of BLM and USFS lands are quite 101. After the road was completed, sand for its ability to persist in settings with a different, with the USFS lands being more movement onto and over the road caused minimum of maintenance where other ‘blocked up’ and less dispersed, their closures and was a major maintenance plants do poorly. Because of these at- management, particularly with respect to concern. An effort was mounted to stabi- tributes, broom and derived cultivars the restrictions of the use of herbicides, is lize active dune areas, much of it utilizing have been produced by nurseries in similar. combined plantings of marram grass California and Washington for several Also, while the return rates for Decker’s (Ammophila arenaria (L.) Link) and broom. decades. Broom has also been imported survey were quite respectable, there were This reduced velocity of sand-moving from other countries for resale. Relative to segments of each of the target categories winds and allowed establishment of other the industry as a whole, production and that did not respond. Data summarized vegetation. By 1955, 3992 ha of dunes had demand for these products has declined, from returned surveys thus result in un- been planted on USFS, state, county and and only a few Oregon nurseries are still derestimates, and correcting for under- private lands along 77 km of coastline be- producing and selling broom products, reporting may give more accurate esti- tween Florence and Coos Bay at a cost of but production is a significant source of mates. $US618 ($A927) ha-1. The BLM planted income for a small number of nurseries. Decker’s survey targeted Oregon land another 506 ha (Parker 1958). The Oregon Association of Nursery- owners and managers exclusively. If eco- In terms of the original rationale for men annually publishes a directory of its nomic impacts for broom are to be repre- planting broom, these early efforts have 1400-odd members, which includes pro- sentative for the western United States, been remarkably successful. Sand en- duction and sales figures volunteered by we must make some assumptions about croachment on roads is now a minor con- participating nurseries. Directories from impacts in Washington and California. cern, stabilized sandy areas have been de- 1991, 1995 and 1997 (Oregon Association Based on the distribution of broom shown veloped as residential and commercial ar- of Nurserymen 1997) were reviewed and in Figure 2, the extent of broom within eas, and productive coniferous forests data extracted on numbers of nurseries each of the states is comparable, and we have established over much of the remain- handling broom and the volume of broom have no other data. British Columbia ing area. they processed. could also be said to have about the same Much of what was, however, termed a Twenty-five Oregon nurseries reported amount of broom as any of the states men- ‘dune problem area’ is now managed by handling broom or related cultivars in tioned (Dorworth et al. 1996). Rough esti- the USFS as the Oregon Dunes National 1997. Ten reported producing or import- mates for adverse economic impacts for Recreation Area (NRA) and considered a ing seedlings, and 23 reported producing the western North America then could be valuable natural resource. Broom and container and/or bareroot plants. Of the about four times those for Oregon. other introduced plants interfere with 10 nurseries reporting handling of seed- Assuming that production and sales current management objectives. The pro- lings, nine reported the quantity they han- of broom products in British Columbia tection of snowy plover (Charadrius dled, and 18 of the 23 nurseries producing and California together equal those of alexandrinus Linnaeus) habitat is an exam- containers/bareroot plants reported Oregon, current direct economic benefits ple. Windswept open beaches, the nesting quantities of production. of broom are on the order of $US350 000 habitat for the plover, decreased with Reported production of broom and de- ($A525 000) annually. Oregon will likely sand stabilization, and the succession of rived cultivars in 1996 totalled 183 500 prohibit production and sales after 1999, vegetation to spruce (Picea sitchensis plants, up from reported production in and this figure might then be halved. (Bong.) Carr.) and coast pine (Pinus 1990 and 1994. The value of 1996 produc- Decker’s study provides us with the per- contorta Dougl.) forest provided cover for tion, at wholesale values of $US0.30 spective to make reasonable and con- predators of plovers and their eggs, such ($A0.45) for seedlings and $US1.25 servative assumptions about treatment as crows, ravens, and skunks. Beach areas ($A1.88) for containers and bareroot stock, and opportunity costs of broom in forest suitable for nesting are closed to public was $US176 250 ($A264 375), an increase regeneration and along roadsides, and if use, and large and expensive projects are in value of more than 45% over earlier re- we assume that British Columbia and the now underway to remove vegetation from ports. other states invest comparable amounts in many areas, and broom is one of the main Washington weed laws prohibit the broom management, we have justification target plants. sale of broom plants and seeds, and the for saying that more than $US11 million Dilemmas like these are not limited to Oregon Department has proposed an ad- ($A16.5 million) annually is directed to the Dunes NRA. Broom has been planted ministrative rule change, which would broom efforts. This figure would not in- along much of the west coast of the United likewise prohibit sales of plants and seeds clude several other important economic States, and there are benefits and costs de- in Oregon. Production and sales of broom cost categories, for example, losses and rived from broom’s role in altering pat- products in California and British Colum- treatment costs in livestock production. terns of succession in coastal areas. bia are unknown, but certainly would be Throughout the area where broom is now much less than those in Oregon. Broom in oceanside dune areas established, it is a direct competitor with Oregon’s coastline measures over 485 km native legumes, and this is especially trou- Discussion of economic impacts of broom north and south. Coastal physiography blesome in the case of the threatened Decker’s (1998) survey captured data from tends to alternate within this reach be- Lupinus sulphureus Dougl. var. kincaidii important major sources, but there are no- tween rocky headlands and sandy dunes (Smith) Hitch., which is the exclusive host table omissions. In forestry, neither the and spits. The sand-based features of Or- of another threatened species, Fender’s holdings of the USDA Forest Service egon’s coast tend to be dynamic and blue butterfly (Icaricia icarioides (USFS) nor those of small woodlot owners ephemeral under natural conditions, but Boisduval). are represented. In western Oregon USFS there have been a number of human ef- Broom is a more successful functional holdings would be roughly equal to those forts to stabilize these areas to allow their analog of lupins in many ecological set- of the BLM, and those of small woodlot use and to permit transit over them. tings, and in this case is encroaching into owners would nearly be so. In designing A north-south federal road was not the natural meadows, which are habitat the survey, Decker determined that the completed along Oregon’s coast until for this lupin. 148 Plant Protection Quarterly Vol.15(4) 2000 Discussion of broom impacts contributions to a control fund, and pros- pests and weeds: a world review’, ed. One of our main interests in understand- pects for continued support are encourag- C.P. Clausen, USDA Agriculture Hand- ing impacts of broom is in having the in- ing. book No. 480, pp. 357-414. (USDA Ag- formation needed to support decisions as ricultural Research Service). to whether to, or how much, we should Acknowledgments Holm, L., Pancho, J.V., Hergerger, J.P. and invest in efforts to manage it. In site-based This work was partially supported by the Plucknett, D.L. (1979). ‘A geographical settings, private industrial foresters Oregon State Office of the US Department atlas of world weeds’. (Wiley- clearly believe that control is necessary, of the Interior Bureau of Land Manage- InterScience, New York). although the documented amount of their ment. Cheryl Decker graciously provided Hosking, J.R., Smith, J.M.B. and Sheppard, annual investment in such control is mod- a copy of her Master’s study and permis- A.W. (1996). The biology of Australian est. Federal land managers are also invest- sion to use data from it. weeds 28. Cytisus scoparius (L.) Link ing in site-specific control in conservation ssp. scoparius. Plant Protection Quarterly efforts other than for forest regeneration, References 11, 102-8. and we can observe other examples of site- Anon. (1998). State noxious-weed weed Lantz, L. (1996). Brooms in Washington. based attempts at controlling broom. Co- requirements recognized in the admin- Unpublished report to The Broom Sym- ordination of large-scale management of istration of the Federal Seed Act. posium, April 17-18, Portland, Oregon. broom is, however, lacking. Individuals (USDA Agriculture Marketing Service Luken, J.O. and Thieret, J.W., eds (1997). and organizations make local decisions on Seed Regulatory and Testing Branch, ‘Assessment and management of plant broom control, but rarely do they cooper- Washington, DC). invasions’. (Springer-Verlag, New ate on management projects even though Balneaves, J.M. (1992). A comparison of York). there is consensus that problems associ- surfactants to aid control of gorse and Oregon Association of Nurserymen. ated with its spread are increasing. Scotch broom with herbicides. Plant (1997). Directory and buyer’s guide. While there is evidence that there is jus- Protection Quarterly 7, 174-77. Oregon Association of Nurserymen, tification for a coordinated project target- Callihan, R.H. and Miller, T.W. (1994). A Milwaukie, Oregon. ing broom, one deterrent is that, in rela- pictorial guide to Idaho’s noxious Parker, K.W. (1958) USDA US Forest Serv- tion to other issues and problems, broom weeds. (Department of Plant, Soil and ice memo from K.W. Parker, Division is not a priority with most landowners Entomological Sciences, University of of Range Management and Wildlife and managers. Even limiting discussion Idaho, Moscow, Idaho). Habitat Research to W.B. Ennis, Crop simply to weed issues, broom would not Decker, C. (1998). Scotch broom: a prelimi- Protections Research Branch, Washing- have highest priority, as other species, nary needs assessment for implementa- ton DC, Sept. 9, 1958. particularly European blackberries (Rubus tion of biological control in western Or- Parsons, W.T. and Cuthbertson, E.G. spp.), generate more interest and concern. egon. Masters Thesis, Department of (1992). ‘Noxious weeds of Australia’. The one opportunity for coordinated Planning, Public Policy and Manage- (Inkata Press, Melbourne and Sydney). efforts directed at broom control that ment, University of Oregon, Eugene, Pojar, J. and MacKinnon, A. (1994). ‘Plants seems practicable at the present time is Oregon. of the Pacific Northwest coast’. (Lone biological control. Throughout western Dorworth, C., Boateng, J., van de Mortel, Pine Publishing, Redmond, Washing- North America, successful control of tansy P. and Ussery, J. (1996). Broom in Brit- ton). ragwort has put biological control in fa- ish Columbia. Unpublished report to Tutin, T.G., Heywood, V.H., Burgess, vour, and there is general support for or- The Broom Symposium, April 17–18, N.A., Valentine, D.H., Walters, S.M. ganizing and sustaining a biological con- Portland, Oregon. and Webb, D.A. (eds) (1968). ‘Flora trol project aimed at broom. Both public Goeden, R.D. (1978). Part II: The biologi- Europaea’. Volume 2. (Cambridge Uni- and private interests have supported cal control of weeds. In ‘Introduced versity Press, Cambridge). research to date through modest parasites and predators of arthropod

agricultural production may result. In the South Island it has been estimated to Status of broom in New Zealand occupy 0.92% of farmable land. In some situations grazing management can con- Simon FowlerA and Pauline SyrettB, tain broom, and where further control is A Landcare Research, Private Bag 92170, Auckland, New Zealand. necessary, herbicides, although expen- B Landcare Research, PO Box 69, Christchurch, New Zealand. sive are effective. Cutting and burning have also been recommended in certain situations. Habitat of nesting native birds on open riverbeds is threatened Summary maximum age and a larger size. It occu- when broom and other scrub species in- Broom (Cytisus scoparius (L.) Link) is the pies open habitats, from sea level to 1200 vade and provide cover for predators. On only broom species that is a declared m, invading native tussock grassland, in- the positive side, broom is regarded as a noxious weed in New Zealand. It was troduced pasture, riverbed and waste- useful pollen source by New Zealand first recorded in the wild in 1872 and is land throughout productive and conser- beekeepers. In some environments it can now widespread and abundant on a vation areas. Broom causes economic play a role in encouraging succession to range of soils (esp. of alluvial or colluvial losses to agricultural and forestry opera- native bush, and in some areas it may origin), particularly the drier eastern side tions, and detracts from conservation val- provide an important spring food source of the South Island and in central North ues. Establishment costs of exotic pine for the native pigeon. However, its nega- Island. The range expansion of broom forests are increased by the need to clear tive environmental effects are much has been most dramatic over the last 50 broom from plantation sites, and re- greater than its positive effects, and a re- years, but it continues to invade new ar- invasion by the weed reduces the rate of cent update of the cost-benefit analysis eas. Broom grows more vigorously in pine growth. Broom is a serious invader for biological control of broom in New many parts of New Zealand than in of pastoral land, particularly in drier hill Zealand showed a clear net benefit from its native range, obtaining a greater country areas, where substantial losses to its control. Plant Protection Quarterly Vol.15(4) 2000 149 experiments in the south of broom’s na- tive range, in southern France. Determinants of broom (Cytisus scoparius (L.) Link) This paper first overviews ecological abundance in Europe knowledge of broom in Europe then presents broom recruitment experiments

A B C B as carried out in the UK and France. Un- Quentin Paynter , Simon V. Fowler , Jane Memmott , Richard H. Shaw published results from the UK are com- D and Andy W. Sheppard pared with the previously published re- A CABI Bioscience, c/o CSIRO, Campus International de Baillarguet, 34980 sults from France (Paynter at al. 1998) Montferrier-sur-Lez, France. which are only summarized here. Results B CABI Bioscience, Silwood Park, Buckhurst Road, Ascot, Berks. SL5 7TA, of these experiments are discussed in rela- United Kingdom. tion to the broom models developed by C Leverhulme Unit: CABI Bioscience/NERC Centre for Population Biology, Rees and Paynter (1997). Imperial College at Silwood Park, Ascot, Berks. SL5 7PY, United Kingdom. Overview of the ecology of broom D CSIRO Entomology, GPO Box 1700, Canberra ACT 2601, Australia. in Europe Seed production cycles between years of Present addresses: high and low production in the UK, with a A CSIRO, Tropical Ecosystems Research Centre, PMB 44, Winnellie, NT 0822, Australia. (a) 240 220 ¡ B Landcare Research, Private Bag 92170, Mt. Albert, Auckland, New Zealand. ¡ 200 C ¡ University of Bristol, Senate House, Tynedall Avenue, Bristol BS8 1TH, 180 ¡ ¡ United Kingdom. 160 ¡ ¡ ● ● 140 ● ¡ ● ● ● ● 120 ● 100 ¡ Summary 1997) and how population parameters in- Height (cm) 80 ● This paper reviews ecological literature teract to make a plant an invasive weed 60 40 and presents previously unpublished (e.g. Rees and Paynter 1997). For example, ●¡ data concerning population dynamics of the spatial population models for broom 20 0 broom (Cytisus scoparius) in Europe. described by Rees and Paynter (1997) pre- 0123456789 These studies, together with recent dict the area occupied by broom by incor- (b) population dynamics modelling, pro- porating measures of disturbance, germi- 70 ) 3 vide strong evidence that insect herbiv- nation, seed bank decay, survival, time to 65 ¡ ores regulate European broom popula- reproduction, longevity, fecundity, seed 60 55 tions, suggesting biological control could dispersal and the probability broom can ¡ 50 succeed in controlling exotic weedy regenerate after a stand dies. This model 45 ¡ populations. Furthermore, grazing by requires detailed knowledge of a plant’s 40 mammalian herbivores and the fre- biology and demography, but reliable es- 35 30 quency of disturbances to the soil sur- timates of all the population parameters ¡ 25 ¡ ¡ face, that create microsites for seedling required are only now becoming avail- 20 ● germination, were also shown to regu- able. 15 ● ¡ ¡ late populations, suggesting that grazing In a long-term chemical exclusion 10 ● ● ● ● and land management strategies could study, Waloff and Richards (1977) showed 5 ● ● 0 ¡ ¡ be useful for the integrated control of insect herbivory dramatically reduced Mean annual seed production (×10 0123456789 weedy exotic populations. broom growth, fecundity and survival (Figure 1, and below), suggesting it might Introduction regulate broom populations in the United (c) 0.5 Broom (Cytisus scoparius (L.) Link) is na- Kingdom (UK). However, fecundity may ● tive to Europe (Tutin et al. 1968) where it have little effect on abundance of woody 0.4 ● can be a minor weed (Gilchrist 1980, shrubs (Andersen 1989). Reducing sur- Rousseau and Loiseau 1982, Thompson vival might not affect a broom infestation 0.3 1988). In New Zealand, Australia and the if gaps made by dying plants are immedi- United States it is a serious introduced ately recolonized by broom seedlings. Un- ● ¡ 0.2 ● weed of pasture, bushland and forestry til recently little population data in rela- ¡ and the target of biological control pro- tion to broom seed bank dynamics and Proportion dead grams (Parsons and Cuthbertson 1992, seedling recruitment has been available. ¡ 0.1 ●●¡ Hosking et al. 1998). This has prevented any conclusive assess- ¡¡¡● ¡¡ ¡ ● ● Studying weed population ecology can ment of whether insect herbivores do in- ● 0.0 reveal why introduced populations are deed regulate European broom popula- 0123456789 weedy (Noble 1989, Crawley et al. 1993), tions. can aid biological control agent selection As part of a multi-national broom bio- Age (years) (Briese 1993, Scott 1996), and provides a logical control program, experiments Figure 1. Effect of regular spraying scientific basis for integrating weed man- were set up to study factors affecting with insecticides on (a) height, (b) agement techniques. The data obtained, broom recruitment in France and the UK when used to develop population models, where broom is native and in Australia fecundity and (c) mortality of ¡ can help predict the effect of biological and New Zealand where it is an exotic broom. Sprayed ( ) and unsprayed control agents on target weed populations weed (Memmott et al. 1993, Fowler et al. (l) plants. From Waloff and (Lonsdale et al. 1995, Rees and Paynter 1996). Paynter et al. (1998) described Richards (1977). 150 Plant Protection Quarterly Vol.15(4) 2000 mean yearly output of about 6600 seeds Unfortunately these plants died prior to which were re-randomized on each sam- plant-1, but about 26 000 seeds plant-1 for treatment allocation (ring-barked by rab- pling date to give statistically independ- insecticide-treated plants, (Waloff and bits). The broom seed bank was known to ent samples across dates. Using a flag Richards 1977, Figure 1b). In France, be significant (M.J. Crawley personal com- composed of coloured tape wrapped yearly fecundity of just 72–728 seeds munication). The 1 m high fences were around a cocktail stick, each broom seed- plant-1 was measured for plants growing made of chicken wire (about 5 cm mesh) ling was marked with a unique identifica- in shady sites and between 1061-5649 supported by large fence posts at the cor- tion number in two permanent quadrats seeds plant-1, for unshaded plants (Rees ners and 1–3 smaller posts along the sides. in each undisturbed, single cultivation and Paynter 1997). Treatments in the UK were allocated by 8 and cut (France only) subplot. The posi- Seeds disperse by pod dehiscence, May 1991. tion of the two permanent quadrats was numbers declining exponentially with Seed banks were sampled using ten cir- deliberately chosen to reflect areas of low distance. Most land within 1 m of parent cular soil-cores (5 cm in diameter by 10 cm and high seedling density in each subplot. plants; a few can be flung up to 5 m deep) taken at random from each subplot. Seedling size and presence of arthropod (Paynter et al. 1996). Broom seeds are Cores were sieved, hand-sorted and the herbivores and fungal pathogens was hard-coated and, typically, only a fraction number of broom seeds with fresh noted in these quadrats on each sampling germinates each year (Paynter et al. 1996). endosperm recorded. In the UK cores date. Age at first flowering and seed set Seed banks build up (Table 1), despite in- were taken in 1991 (prior to treatment al- since disturbance treatment allocation tense vertebrate seed predation on the soil location) and in 1995 after seed fall so the was noted for all plants in sample surface (>90%, Paynter et al. 1996). Seed- effect of disturbance on the proportion of quadrats. lings do not survive beneath broom stands seed germinating could be determined, In the competition and pesticide experi- and broom is often found on disturbed while in France cores had been taken an- ments only used in France seedlings soils in Britain (Waloff 1968). Rousseau nually after seed fall (Paynter et al. 1998). within each quadrat/subplot were la- and Loiseau (1982) also recognized the Two subplots per plot were cleared and belled and measured as in the permanent importance of disturbance, by fire or me- cultivated, to approximately 10 cm depth quadrats above. chanical clearing, for seedling establish- to provide a major disturbance event at the ment in France. High temperature that start of the experiment. One of these sub- Statistical analysis would occur in a fire breaks dormancy of plots was then repeatedly re-cultivated Analyses of the UK experiments were per- broom seeds (Tarrega et al. 1992, Bossard each summer as in France. At least one re- formed using the GLIM statistical package 1993). maining subplot per plot went undis- (McCullagh and Nelder 1983). Analyses of Broom has an average life expectancy turbed to act as controls. deviance were performed to study varia- of 10–12 years in the UK (Waloff and Several additional treatments were tion in the size of seed banks and the pro- Richards 1977, Rees and Paynter 1997), used in France (Paynter et al. 1998): (a) one portion of the seeds that germinated. Fac- and does not live more than c. 12 years in subplot per plot was cleared of broom by tors tested were plot, fence treatment France (Rousseau and Loiseau 1982, Rees cutting plants at ground level, leaving the (fenced or unfenced), time (1991 or 1995 and Paynter 1997). A large scale insecti- soil undisturbed, (b) hand-weeded com- seed counts) and disturbance treatment cide application experiment performed in petition treatments within a 5 × 10 m (undisturbed, single, and annual cultiva- the UK led to about a 50% reduction in fenced, cleared and cultivated area tion). Seed bank counts were log (n+1) plant mortality over a ten-year period (Mandagout only), where a grid of thirty transformed to normalize them prior to (Waloff and Richards 1977, Figure 1c). 0.25 m2 quadrats was set up to generate analysis. Other analyses tested whether initial seedling densities of 5, 20 or 80 plot, fence treatment and disturbance (un- Methods used for European broom seedlings per quadrat and left to grow disturbed and single cultivation) affected recruitment experiments with or without competing species, (c) in- the proportion of seedlings surviving at In the UK, plots were set up in the grounds secticide, molluscicide, fungicide and con- each census and whether disturbance, of Imperial College at Silwood Park, Berk- trol treatments (applied three times a year) fence treatment, site and time affected per- shire (Lat. 51° 24'N, Long. 0° 34'W) at an allocated to 2.5 × 5 m subplots within a 10 centage cover of broom and competing altitude of 61 m (see Waloff 1968, × 10 m fenced, cleared and cultivated area vegetation. In these analyses the factor Memmott et al. 1993). In southern France, (see details in Paynter et al. 1998). ‘time’ was assigned seven levels, corre- plots were set up at Mandagout and Broom was sampled within subplots sponding to the first sample date of seed- L’Esperou, for site descriptions see using both ‘random’ and ‘permanent’ 0.5 lings and the subsequent summer samples Paynter et al. 1998. × 0.5 m quadrats where censuses were for each of the six summers (1992-1997). The experiments used paired unfenced performed three times per year in spring Annual cultivation was excluded from and fenced plots to exclude grazing mam- (April/May), summer (July/ August) and these analyses as it killed all seedlings. All mals. These plots were divided into 5 × 5 autumn (November/early December). proportion data were analysed after angu- m sub-plots. In the UK, four paired 10 × 20 The number of broom seedlings and the lar transformation. Where analyses re- m plots were used, these had senescent approximate percentage cover of all plant vealed significant treatment effects, least plants left over from extensive broom species were recorded in four randomly significant difference (LSD) multiple stands that had been present in the previ- positioned quadrats in each undisturbed, range tests were performed to compare ous decade just prior the experiment. cultivated and cut (France only) subplot, treatment pairs, according to Crawley (1993). Analysis of the French data was et al. -2 similar and is described by Paynter Table 1. Seed banks beneath broom in the native range (seeds m ). (1998). Seed bank Site Country ReferenceA Results 5293–5405 Silwood Park, Berkshire UK Seed banks 3392–6733 County Wicklow Eire 1 The seed bank in the UK averaged (± s.e.) c. 3000 (968–19664) Abandoned terraces, Gard France 2 5405 (± 655) m-2 in 1991 and 5293 (± 770) 460–1405 Gard France 3 m-2 in 1995, and was of similar magnitude 595 Vinuesa Spain 3 to that observed in France (Table 1), but A Reference: 1 Smith and Harlen (1991); 2 Paynter et al. (1998); 3 Hosking (1995). only varied significantly between plots Plant Protection Quarterly Vol.15(4) 2000 151

(F3,40 = 5.33, P<0.01). The seed banks were subplots. However, there was no signifi- Table 2. Analysis of deviance for not observed to decline by about 50% each cant effect of intra- or interspecific compe- the proportion of the broom seed year as observed without seed replenish- tition on survival in the competition ex- bank germinating in 1991 and 1995. ment in France (Figure 1 in Paynter et al. periment in France, although seedling 1998). This is probably because mature height declined with increasing initial Source d.f. F-ratio seeding plants had regenerated in most seedling density (Figure 8 in Paynter et al. Plot 3 2.80 plots by the time the seed banks were sam- 1998). There was also no significant effect Cultivation 2 3.59* pled in 1995. of pesticide application on seedling estab- Fence treatment 1 0.48 lishment from the French experiment. Year 1 17.25*** Germination rates Error 40 In both the UK and France, germination Seedling growth and flowering Interaction was virtually confined to spring. The pro- In the UK, seedlings reached a mean Cultivation × Year 2 3.34* portion of seeds germinating was highest height of about 80 cm after just 24 months, Error 38 in disturbed subplots, both in the UK (Ta- setting seed after 27 months and attaining ble 2, Figure 2) and France (where germi- a maximum height of 210 cm after 63 *P<0.05; ***P<0.001 nation was also correlated to March rain- months. In France plants grew slower fall; Figure 3 in Paynter et al. 1998). In the UK germination in 1991 was highest in initially cultivated subplots and in 1995, 3.0 germination was significantly higher in annual cultivation subplots than in both Undisturbed control and single cultivation subplots, SC where germination was negligible (Figure 2.5 AC 2). b

Survival 2.0 In both the UK and France, no seedlings survived to flowering age under a broom canopy, even if it had only been estab- lished for one year. Survival, therefore, 1.5 b was confined to the first cohorts following allocation of treatments: no second- or a later-cohort seedlings survived more than 1.0 a few weeks in either France (Figure 4 in Percentage germination Percentage Paynter et al. 1998) or the UK (Figure 3). In the UK, the major factor influencing 0.5 a seedling survival was grazing. In fenced a and unfenced cultivated plots about 60% and 0% of first-cohort seedlings survived to flowering age respectively (Figure 3). 0.0 Survival of first-cohort (spring 1991) seed- 1991 1995 lings was not significantly affected by cul- Year tivation (Table 3). In France, about 14% of seedlings survived to flowering age

Figure 2. Percentage of seeds123 germinating each year (± s.e.) in the UK, for

(fenced and unfenced plots combined; 123 the disturbance treatments: 123 = undisturbed; = single initial Figure 4 in Paynter et al. 1998). Survival of 1234 1234 first-cohort seedlings was higher in sub- cultivation; 1234 = annual cultivation. Columns within the same year with plots that were cultivated once than in cut the same letter are not significantly different.

(a)100 (b) 40 (a) Fenced Unfenced (b)

80 Fenced 30 Unfenced

60 20 40

10 20 Percentage survival Percentage survival

0 0 12 24 36 48 63 75 61224 Time (months) Time (months)

Figure 3. Percentage of seedlings surviving to each census in the UK (± s.e.) in both fenced and unfenced plots. For: (a) first cohort of seedlings that germinated in Spring 1991, where Time = time from the spring census 1991, and (b) second cohort of seedlings that germinated in spring 1992, where Time = time from the spring census 1992. 152 Plant Protection Quarterly Vol.15(4) 2000 Table 3. Analyses of deviance for Table 4. Analysis of deviance for Table 5. Analysis of deviance for the proportions of broom seedlings percentage cover of vegetation percentage broom cover (n.b. there from the first cohort surviving to competing with broom (n.b. there are 4 missing values). each census in the UK experiment. are 4 missing values). Source d.f. F-ratio Source d.f. F-ratio Source d.f. F-ratio Plot 3 10.23** 12 month census Plot 3 4.57* Cultivation 1 0.43 Plot 3 0.30 Cultivation 1 1.09 Fence treatment 1 112.19*** Cultivation 1 0.88 Fence treatment 1 0.49 Time 6 4.41*** Fence treatment 1 120.67*** Time 6 3.11** Error 96 Error 8 Error 96 Interactions 24 month census Interactions Plot × Cultivation 3 2.72 Plot 3 4.61* Plot × Cultivation 3 1.18 Plot × Fence treat. 3 20.2*** Cultivation 1 0.01 Plot × Fence treat. 3 7.76** Plot × Time 18 1.14 Fence treatment 1 53.93*** Plot × Time 18 2.59 Fence treat. × Cult. 1 0.04 Error 8 Fence treat. × Cult. 1 0.07 Fence treat. × Time 6 15.76*** 75 month census Fence treat. × Time 6 5.87*** Cultivation × Time 6 0.71 Plot 3 4.61* Cultivation × Time 6 0.24 Error 59 Cultivation 1 0.01 Error 59 Fence treatment 1 17.89** ***P<0.001 Error 8 *P<0.05; **P<0.01; ***P<0.001

*P<0.05; **P<0.01; ***P<0.001 varied significantly with fence treatment, plot and time (Table 5, Figure 4b). Within than in the UK. The mean fenced plots it declined from about 60%, height of surviving seedlings in recorded 3 months after allocation of treat- 100 (a) single cultivation and cut sub- ments to about 15% after 75 months as (a) 90 Unfenced plots was about 80 cm after 39 competing broom regenerated. In con- months. During their fourth trast, for unfenced plots, percentage cover 80 Fenced year 39% of surviving plants of competing vegetation showed no obvi- 70 flowered, although most flow- ous trend over time and averaged 40–50%. ers aborted so only 7% of plants In France, percentage cover of broom 60 set seed and the mean seed pro- was not affected by site or fence treatment, 50 duction was just 38.3 seeds m-2. but was significantly affected by time and

40 In the French experiment cultivation (Paynter et al. 1998). French interspecific competition sig- sites, unlike UK sites, had mature broom 30 Percentage cover Percentage nificantly affected fecundity. cover which remained relatively constant

20 After just 27 months nearly 10% in undisturbed subplots. However, four of surviving plants set seed in years after allocation of treatments, per- 10 the no competition treatment, cent broom cover in the single cultivation

0 whereas only 0.3% of plants ex- plots was also over 60% and an order of 3 122739516375posed to interspecific competi- magnitude higher than in cut plots (Fig- Time (months) tion set seed. There was no ef- ure 6 in Paynter et al. 1998). Time and cul- fect of pesticide application on tivation also significantly affected per- the minimum age of reproduc- centage cover of competing vegetation at tion. However, insecticide- the French sites (Figure 7 in Paynter et al. (b) 100 (b) Unfenced treated plants had a signifi- 1998). Within 2 years percent cover of 90 Fenced cantly reduced flower abortion competing vegetation within cut plots had 80 rate and, as in Waloff and risen from 20 to 90%, while it never 70 Richards (1977), produced reached more than 60% in the cultivated

60 more seeds per pod and over plots and scarcely changed within single- three times more seeds per cultivation plots. 50 plant than unsprayed controls 40 (Groves and Paynter 1998). Discussion 30 The UK study revealed similarities in Percentage cover 20 Percentage cover broom recruitment to southern France In the UK subplots, percentage (Paynter et al. 1998), germination was 10 cover of broom was signifi- highest in cultivated subplots and seed- 0 cantly affected by plot, fence ling survival to flowering was confined to 3 122739516375 treatment and time (Table 4, the first cohort. Seedling survival beneath Time (months) Figure 4a), but not cultivation. established stands was negligible. Graz- The percentage cover of broom ing in the UK, however, was more intense Figure 4. Percentage cover of (a) broom and (b) increased from about 5% after (mainly by rabbits) and had a dramatic ef- the first census to 70% after 75 fect there on seedling survival (Figure 3). competing vegetation versus time (months) for months within the fenced plots, Plants flowered in their third year in the both fenced and unfenced plots (cultivated and while in unfenced plots it re- UK plots, taking no longer to reach matu- undisturbed combined) in the UK. Time = time mained negligible throughout rity than in exotic habitats in New Zealand since first census following allocation of the experiment. The percentage and Australia (Williams 1981, Smith and disturbance treatments. cover of competing vegetation Harlen 1991), compared to France, where Plant Protection Quarterly Vol.15(4) 2000 153 flowering was delayed a further year Paynter et al. (1998) argued 1.0 (a) (Paynter et al. 1998). Although first-cohort seed bank depletion is most 0.9 (a) seedling survival was higher within rapid at the soil surface because fenced plots in the UK than France, this buried seeds are more likely to 0.8 may simply have been because the first escape predation (Hulme 1994) 0.7 census was performed later and some and less likely to germinate 0.6 seedling death may have gone unre- (Tran and Cavanagh 1984, corded. Bossard 1993, Lonsdale 1993). 0.5 Stand regeneration was not affected by Furthermore, broom seedlings 0.4 cultivation in the UK, but was faster in the failed to emerge from seeds 0.3 cultivated plots in France (Figure 6 in planted at depths greater than 0.2 Paynter et al. 1998). Although there were about 5 cm (Williams 1981, differences in the germination rates be- Bossard 1993). Therefore, al- 0.1 tween countries, there are other reasons though buried seed has the po- 0.0 for this. Firstly, the undisturbed treatment tential to survive for years, per- 0.0 0.2 0.4 0.6 0.8 1.0 in the UK had no live mature broom re- haps decades (Turner 1934), Probability of disturbance maining at the start of the experiment, disturbance is necessary to Probability of disturbance while the undisturbed treatment in France bring them close enough to the 1.0 comprised of broom stands with almost soil surface to germinate and (b)(b) complete canopies. The UK undisturbed emerge, and to disrupt compet- 0.9 treatment was therefore more similar to ing vegetation that might pre- 0.8 the ‘cut’ treatment in France and behaved vent seedling establishment. 0.7 accordingly. Secondly, the field site at The presence of a long-lived Silwood Park is heavily grazed by rabbits seed bank may explain how 0.6 (Crawley 1990) compared to just the infre- populations can reappear after 0.5 quent passage of a few goats and cattle in long periods without distur- 0.4 France (Paynter et al. 1998). Even the un- bance, but it cannot explain the 0.3 disturbed treatment in the UK had a persistent presence of a dense rather degraded herb layer that did not stand of broom (Rees and 0.2

compete strongly with emerging broom Paynter 1997). Proportion of sites with broom0.1 Proportion of sites with broom seedlings. The site could, therefore be con- The wide range of processes 0.0 sidered ‘inherently disturbed’. Therefore, summarized by the term distur- 0 1020304050 disturbance may still be an important fac- bance complicates characteriz- tor affecting establishment of broom seed- ing and quantifying the effect of LongevityLongevity (years) lings in the UK. disturbance. While our experi- 1.0 ments used only cultivation, (c)(c) Modelling broom population disturbance also represents, for 0.9 dynamics example, fire, landslide, flood- 0.8 All parameters identified by Rees and ing, frost heavage, grazing and 0.7 Paynter (1997) had been investigated by at trampling by horses and feral 0.6 least one experimental study in Europe pigs. Broom may have become described above. Rees and Paynter (1997) a more significant weed in ex- 0.5 investigated importance of individual pa- otic habitats because of differ- 0.4 rameters by varying each parameter while ences in disturbance rates, but 0.3 keeping all other parameters constant and more studies are required to 0.2 at levels typically found in Europe. They quantify and characterize dis-

showed the proportion of sites occupied turbances that affect broom. Proportion of sites with broom 0.1 was largely determined by disturbance, 0.0 longevity of broom plants and probability Longevity 0.0 0.2 0.4 0.6 0.8 1.0 of recolonization after stands die (Figure Increased longevity of broom Probability a site can be 5). plants was predicted to have re-colonized by broom profound effects on broom Disturbance abundance (Figure 5b). This is Figure 5. Predicted proportion of sites with Studies described above showed distur- largely due to space being occu- broom versus (a) probability of disturbance (b) bance enhances germination and seedling pied for longer – so that at any longevity of broom plants and (c) probability a survival. The model predicted a non-lin- given time more space will be site is suitable for recolonization by broom, ear relationship between disturbance and occupied. However, there are after senescence of the original stand. From broom cover (Figure 5a). Low levels of dis- other consequences of in- Rees and Paynter (1997). turbance result in few opportunities for creased broom longevity. seedling establishment as seen in the lack Firstly, increased longevity will of seedling survival under mature broom. result in higher seed production over a due the absence of specialist insect herbiv- Conversely, high levels of disturbance, as plant’s lifetime. Secondly, denser stands ores (Waloff and Richards 1977), so it ap- in the annual cultivation treatment, allow that persist longer may result in greater pears that insects are at least partially re- extensive establishment, but kill seedlings depletion of competing vegetation and sponsible for regulation of European before they attain reproductive age, lead- their seed banks. This may have conse- broom populations. ing ultimately to seed bank extinction. quences for the probability of self-replace- There is, however, a large range of inter- ment (see below). Broom lives longer in Probability of self-replacement mediate disturbance intensities where exotic habitats than in Europe (Rees and If the soil surface is colonized by compet- broom persists. Paynter 1997) and this is considered to be ing plants, following the death of a plant, 154 Plant Protection Quarterly Vol.15(4) 2000 broom seedlings may fail to establish. Un- where broom is an exotic weed, intro- (Bossard 1993). However, burning will be der these circumstances, overall occu- duced biological control agents can reach much more damaging to competing pancy by broom will be lower than if seed- much greater levels of abundance when ground flora than, for example, selective lings can recolonize the parental site (Fig- released from their own natural enemies herbicide treatment or slashing and, there- ure 5c). In France, few seedlings estab- and competitors to become much more fore, more likely to be accompanied by ex- lished where broom stands were cut damaging, as has been seen for a number tensive regeneration unless options 2 and away, stimulating vigorous regrowth of of broom agents already released (Syrett 3 (above) are also performed. More work perennial grasses and herbs that had per- et al. 1999). will also be required to study how these sisted beneath stands (Paynter et al. 1998). strategies can best be integrated to mini- In Europe, generally, stands do not appear Other control strategies mize their impact on populations of bio- to regenerate after senescence although Controlling broom stands by chemical or logical control agents. This study has at there is some evidence that they do in physical means, such as by herbicide, least helped outline important factors af- Australia (A. Sheppard personal observa- burning and slashing, creates disturbance, fecting broom regeneration in the native tion). which breaks seed dormancy and creates range. the best conditions for establishment. Other factors Thus, all these methods are likely to re- Acknowledgments The models did not suggest that variation quire subsequent control treatments, Quentin Paynter, Simon Fowler and Rich- in seedling survival is important because within two years (i.e. before the regenerat- ard Shaw were funded by the New South broom produces so many seeds and seed- ing seedlings are able to reproduce), to Wales government through its Environ- lings that only mortality rates close to prevent extensive regeneration. Indeed, mental Trusts and by New South Wales 100% can reduce broom cover (Rees and where burning or mechanical control is National Parks and Wildlife Service, State Paynter 1997). However, in the UK experi- used in France it provides a temporary so- Forests and Hunter Pastoral Company ment, grazing did have a dramatic effect lution, but often eventually results in the (these funds were administered by the on broom populations by achieving such establishment of an even denser broom Management Committee for the Biological a high level of mortality. stand unless the stocking rate is increased Control of Scotch Broom). Jane Memmott Rees and Paynter (1997) predicted de- and/or revegetation with native grasses is was funded by the Leverhulme Trust, laying flowering by several years would performed (Rousseau and Loiseau 1982). Natural Environment Research Council significantly reduce the area of suitable The results of the modelling also suggest and the Royal Society. Andy Sheppard habitat covered by broom. However mini- repeated ploughing to deplete the seed was funded by the Australian Govern- mum age for reproduction, at least in the bank could also be effective (see also Par- ment. We thank Mark Lonsdale, David UK experiment, was the same as has been sons and Cuthbertson 1992). Grazing Briese, Penny Edwards and John Hosking recorded in exotic habitats in Australia could be a major tool for broom control, for their comments on drafts of this manu- and New Zealand where this plant is a by preventing re-establishment of stands script. major weed (Williams 1981, Smith and from the seed bank following stand clear- Harlen 1991). Paynter et al. (1998) showed ance. However, more work will be needed References that in France interspecific competition, to establish whether the results described Andersen, A.N. (1989). How important is rather than pathogens and arthropod her- above, pertaining to rabbit grazing, are seed predation to recruitment in stable bivores (which are slow to colonize seed- relevant to other grazing animals. Indeed, populations of long-lived perennials? lings), can increase the pre-reproductive broom abundance has been linked to graz- Oecologia 81, 310-15. period, although flowering one year later ing by cattle in New Zealand (Williams Bossard, C.C. (1993). Seed germination in is probably unimportant. Heavy browsing 1983). This approach may not be appropri- the exotic shrub Cytisus scoparius by herbivorous mammals, not considered ate for every circumstance, such as in na- (Scotch broom) in California. Madroño in these studies however, could poten- tional parks, and subsequent relaxation of 40, 47-61. tially delay flowering considerably. grazing could create ideal conditions for Briese, D.T. (1993). The contribution of seedling establishment from the seed plant biology and ecology to the bio- Implications for the control of bank. Manipulating interspecific competi- logical control of weeds. Proceedings of broom tion may also form an important tool for the 10th Australian Weed Conference Biological control broom management. Rousseau and and 14th Asian-Pacific Weed Science The results of these studies suggest the Loiseau (1982) noted that revegetation Society Conference, 6–10 September prospects for biological control of broom with seeds of the perennial grass, Dactylis 1993, Brisbane, eds J.T. Swarbrick, in exotic habitats are good, provided glomerata L., reduced broom population C.W.L. Henderson, R.J. Jettner, L. Streit sufficiently specific agents can be found. density in pasture two years after me- and S.R. Walker, Volume 1, pp. 10-8. Insect herbivores can reduce life expect- chanical clearing. (Weed Science Society of Queensland, ancy of broom plants (Waloff and A tentative management strategy Brisbane). Richards 1977) and this should have a dra- might involve: Crawley, M.J. (1990). Rabbit grazing, plant matic effect on broom populations (Rees 1. Initial clearance of a stand by mechani- competition and seedling recruitment and Paynter 1997). Seed-feeders will re- cal or chemical means or by fire. in acid grassland. Journal of Applied duce rate of invasion into new habitats 2. If necessary, a selective spray or Ecology 27, 803-20. (Paynter et al. 1996) and may even lead to ploughing treatment within two years Crawley, M.J. (1993). ‘GLIM for ecolo- a decline in broom populations in fre- and/or: gists’. (Blackwell Scientific Publica- quently disturbed habitats such as 3. Revegetation with pasture grasses tions, Oxford). braided river beds in New Zealand (Rees and/or stocking with sheep or goats. Crawley, M.J., Hails, R.S., Rees, M., Kohn, and Paynter 1997). Furthermore, chronic More work will be required to develop an D. and Buxton, J. (1993). Ecology of effects of insect herbivory on plant longev- optimal integrated strategy for control of transgenic oilseed rape in natural habi- ity, size and vigour (Waloff and Richards broom, as there are likely to be both ad- tats. Nature, 363, 620-23. 1977) might explain why perennial vantages and disadvantages to the vari- Fowler, S.V., Harman, H.M., Memmott, J., grasses and herbs, which can smother ous options. For example, burning kills Paynter, Q., Shaw, R., Sheppard, A.W. seedlings, persist beneath native but, ap- stands and depletes the seed bank by kill- and Syrett, P. (1996). Comparing the parently, not exotic stands. Moreover, ing seed and stimulating germination population dynamics of broom, Cytisus Plant Protection Quarterly Vol.15(4) 2000 155 scoparius, as a native plant in the United McCullagh, P and Nelder, J.A. (1983). Scott, J.K. (1996). Population ecology of Kingdom and France and as an inva- ‘Generalized linear models’, 2nd edi- Chrysanthemoides monilifera in South Af- sive alien weed in Australia and New tion. (Chapman and Hall, London). rica: implications for its control in Aus- Zealand. Proceedings of the Ninth In- Memmott, J., Fowler, S.V., Syrett, P. and tralia. Journal of Applied Ecology 33, ternational Symposium on Biological Hosking, J.R. (1993). What makes 1496-508. Control of Weeds, 21–26 January 1996, broom a major problem? Proceedings Smith, J.M.B. and Harlen, R.L. (1991). Pre- Stellenbosch, South Africa, eds V.C. of the Brighton Crop Protection Confer- liminary observations on the seed dy- Moran and J.H. Hoffman, pp. 19-26. ence. Brighton, 22–25 November 1993, namics of broom (Cytisus scoparius) at (University of Cape Town, Cape Brighton, United Kingdom, pp. 753-8. Barrington Tops, New South Wales. Town). (British Crop Protection Council, Plant Protection Quarterly 6, 73-8. Gilchrist A.J. (1980). Control of woody Farnham, UK). Syrett P., Fowler S.V., Coombs E.M., weeds in forestry with triclopyr. Pro- Noble, I.R. (1989). Attributes of invaders Hosking J.R., Markin G.P., Paynter Q.E. ceedings of the Conference on Weed and the invading process: Terrestrial and Sheppard A.W. (1999). The poten- Control in Forestry, 1–2 April 1980, and vascular plants. In ‘Biological inva- tial for biological control of Scotch Nottingham, United Kingdom, pp. sions: a global perspective’, eds J.A. broom (Cytisus scoparius) (Fabaceae) 249-56. Drake, H.A. Mooney, F. di Castri, R.H. and related weedy species. Biocontrol Groves, R.H. and Paynter, Q. (1998). Com- Groves, F.J. Burger, M. Rejmanek and News and Information 20, 17N-34N. parative ecology of Cytisus scoparius in M. Williamson, pp. 301-10. (J. Wiley & Tarrega R., Calvo L. and Trabaud L. France and Australia. Proceedings of Sons, Chichester). (1992). Effect of high temperatures on the Sixth EWRS Mediterranean Sympo- Parsons, W.T. and Cuthbertson, E.G. seed germination of two woody sium, 13–15 May 1998, Montpellier, (1992). ‘Noxious weeds of Australia’. Leguminosae. Vegetatio 102, 139-47. France, pp. 119-25. (Inkata Press, Melbourne and Sydney). Thompson A.R. (1988). Fluroxypyr, a new Hosking, J.R. (1995). The impact of seed Paynter, Q., Fowler, S.V., Hinz, H.L., herbicide for scrub and woody weed and pod feeding insects on Cytisus sco- Memmott, J., Shaw, R., Sheppard, A.W. control in forestry and amenity areas. parius (L.) Link. Proceedings of the and Syrett, P. (1996). Are seed-feeding Aspects of Applied Biology 16, 177-82. Eighth International Symposium on insects of use for the biological control Tran, V.N. and Cavanagh, A.K. (1984). Biological Control of Weeds, 2-7 Febru- of broom? Proceedings of the Ninth In- Structural aspects of seed dormancy. In ary 1992, Lincoln University, Canter- ternational Symposium on Biological ‘Seed Physiology, Volume 2, Germina- bury, New Zealand, eds E.S. Delfosse Control of Weeds, 21–26 January 1996, tion and Reserve Mobilisation’, ed. D.R. and R.R. Scott, pp. 45-51. (DSIR/ Stellenbosch, South Africa, eds V.C. Murray, pp. 1-44. (Academic Press, CSIRO, Melbourne). Moran and J.H. Hoffman, pp. 495-501. London). Hosking, J.R., Smith, J.M.B. and Sheppard, (University of Cape Town, Cape Turner, J.H. (1934). The viability of seeds. A.W. (1998). Cytisus scoparius (L.) Link Town). Bulletin of Miscellaneous Information, ssp. scoparius. ‘The biology of Austral- Paynter, Q., Fowler, S.V., Memmott, J. and Kew 6 (1933), 257-69. ian weeds’, Volume 2, eds F.D. Panetta, Sheppard, A.W. (1998). Factors affect- Tutin, T.G., Heywood, V.H., Burges, N.A., R.H. Groves and R.C.H. Shepherd, pp. ing the establishment of Cytisus scopar- Moore, D.M., Valentine, D.H., Walters, 77-88. (R.G. and F.J. Richardson, Mel- ius in southern France: implications for S.M. and Webb, D.A.eds (1968). ‘Flora bourne). managing both native and exotic Europaea’, Volume 2, p. 89. (Cam- Hulme, P.E. (1994). Post-dispersal seed populations. Journal of Applied Ecology bridge University Press, Cambridge). predation in grassland: its magnitude 35, 582-95. Waloff, N. (1968). Studies on the insect and sources of variation. Journal of Ecol- Rees, M. and Paynter, Q. (1997). Biological fauna on Scotch broom Sarothamnus sco- ogy 82, 645-52. control of Scotch broom: modelling the parius (L.) Wimmer. Advances in Ecologi- Lonsdale, W.M. (1993). Losses from the determinants of abundance and the po- cal Research 5, 87-208. seed bank of Mimosa pigra: soil micro- tential impact of introduced insect her- Waloff, N. and Richards, O.W. (1977). The organisms vs. temperature fluctua- bivores. Journal of Applied Ecology 34, effect of insect fauna on growth mortal- tions. Journal of Applied Ecology 30, 1203-21. ity and natality of broom, Sarothamnus 654-60. Rousseau, J. and Loiseau, A. (1982). Struc- scoparius. Journal of Applied Ecology 14, Lonsdale, W.M., Farrell, G. and Wilson, ture et cycle de development des 787-98. C.G. (1995). Biological control of a peuplements a ‘Cytisus scoparius L.’ Williams, P.A. (1981). Aspects of the ecol- tropical weed: a population model and dans le chaine des puys. Acta Oecologia ogy of broom (Cytisus scoparius) in Can- experiment for Sida acuta. Journal of Ap- Applicata 3, 155-68. terbury, New Zealand. New Zealand plied Ecology 32, 391-9. Journal of Botany 19, 31-43. 156 Plant Protection Quarterly Vol.15(4) 2000 first experiment was set up in the UK in 1991 and the last in Australia in 1993 Factors affecting broom regeneration in Australia and (Memmott et al. 1993, Fowler et al. 1996). their management implications Seedlings were followed through to seed production in all countries; data from the

A B C two European countries have been pub- Andy Sheppard , Peter Hodge and Quentin Paynter lished (Memmott et al. 1993, Paynter et al. A CRC Weed Management Systems, CSIRO Entomology, GPO Box 1700, 1996, 1998, 2000). This paper describes the Canberra, Australian Capital Territory 2601, Australia. Australian experiment and summarizes B CRC Weed Management Systems, NSW Agriculture, c/o CSIRO Entomology the first preliminary data from either of GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia. the two invaded countries. The results are C CSIRO, Tropical Ecosystems Research Centre, PMB 44, Winnellie, Northern briefly discussed in relation to conclusions Territory 0822, Australia. drawn about factors affecting broom re- cruitment from the two European coun- tries.

Summary Methods Broom regeneration following distur- ground flora diversity in invaded ecosys- Sites and design of recruitment bance, with and without vertebrate her- tems and generate a false understorey, but experiment bivores, was studied at three contrasting it also harbours feral pigs which perpetu- The experiment used a series of 5 × 15 m sites with differing abundances of native ate the disturbance cycle. Many of these plots set up in (a) broom at least 15 m into plant species in the Shoalhaven River suitable habitats are still broom-free in mature stands and (b) areas of immature system in southern New South Wales. Australia, but are at great risk given the (pre-flowering) broom along the expand- This study was part of a larger experi- wide distribution of at least isolated ing stand edge. Two locations were used, ment replicated across four countries in broom plants in Australia and the inva- 50 km apart along the Shoalhaven River both the native and exotic range of sion history of this species worldwide system in the Southern Tablelands of New broom. In Australia broom seedbanks of (Hosking et al. 1998). To address the threat South Wales. The experiment commenced 6000 to 20 000 seeds m-2 had a natural de- of invasion and problems caused by in spring (November) 1993. cay rate of 36% per annum. The propor- broom in the 200 000 ha already invaded At Krawarree, altitude c. 600 m above tion of the seedbank that germinated in Australia, it is vital to understand why sea level (35°48'S 149°40'E), broom had each year was highly variable, but suffi- this species is able to invade and persist in formed a 5 ha solid stand across the un- cient to be the major cause of seedbank Australian ecosystems. Such understand- fenced border of a cattle property and the decline. Seedling survival and broom ing will be the key to developing effective Deua National Park. It had been fenced off height after three years were similar for management strategies, both to prevent from cattle and left 15 years prior to the all cohorts germinating during the first invasion and suppress dominance of experiment, but the whole stand had open three years of this study. Seedling sur- broom. One way to refine broom manage- access to numerous macropods, wombats vival was higher following cultivation, ment is to compare ecological characteris- and rabbits from the adjacent national with grazing and in immature broom tics of broom between areas where it has park. At this locality, site 1 (Krawarree stands versus mature broom stands, but become a dominant weed and areas where ‘improved’) was set up as two pairs of lower in sites with a higher native com- it is not considered a problem despite a plots, one in mature and the other in im- ponent to the grassland. Broom height long history of presence (Noble 1989). The mature young broom on the ‘improved’ after three years was greater when broom latter state for many such exotic weeds pasture side of the broom stand otherwise was cut and/or the ground cultivated and usually only occurs within the native dominated by the introduced perennial in immature broom stands, but was un- range. grass, Phalaris aquatica L. (Table 1). One affected by grazing. The age when As part of a multi-national broom bio- plot in each pair was fenced to keep out broom first flowered varied from three to logical control program, comparable ex- animals from the size of rabbits to cattle. five years across sites and treatments and periments were set up to study factors af- Fencing material consisted of mesh (mesh was influenced by competition within fecting broom regeneration through re- size approx 5 cm) with large corner fence the grassland and by grazing. These pre- cruitment in France and the UK where it is posts to a height of 1.5 m and depth of 0.5 liminary results are compared with simi- native and rarely considered a weed m in the soil. Site 2 (Krawarree ‘native’) lar data from the native range of the (Rousseau and Loiseau 1982, Thompson consisted of two unfenced plots set up on weed. Implications of these results for 1988) and in Australia and New Zealand the national park side of the broom stand broom management are also discussed. where it is a highly invasive exotic weed in infested native grassland dominated by (Hosking et al. 1998). Additional aims of Poa labillardieri Steud., Microlaena stipoides Introduction these studies were: (a) to complete under- (Labill.) R.Br. and Themeda australis (R.Br.) In its native range broom (Cytisus scopar- standing of whether insects regulate Eu- Stapf; one in mature and other in imma- ius (L.) Link) is a common leguminous ropean broom populations (Paynter et al. ture broom (Table 1). shrub typical of heaths and other acid 2000) taking into account a previous study The third site, named ‘Waterboard’ af- soils in areas of temperate climate (Tutin that measured impact of insects on broom ter the utility responsible for the area, was et al. 1968). Following introduction to Aus- survival and fecundity (Waloff and a cattle and sheep grazed paddock alti- tralia for its many historic, cultural and Richards 1977); (b) to help understand tude c. 500 m (35°17'S 149°48'E), on the horticultural uses (Hosking et al. 1998, which insects may have the greatest im- west bank of the Shoalhaven River. Here Smith 2000), broom has spread, usually pact on exotic broom infestations; (c) to the broom formed a 30 m wide solid strip from homesteads or small (often mining) understand why broom is such an inva- parallel to the river and separated from it hamlets near native bushland, to invade a sive weed in its exotic range; and (d) to by an equivalent strip of blackberry (Ru- number of montane parks, forests and obtain reliable data for key broom popula- bus discolor Weihe & Nees). The broom river systems in temperate Australia. In tion parameters to allow further develop- stand was of mixed aged with some senes- these systems, broom poses the most sig- ment of a population model for broom cence amongst the largest individuals and nificant threats as, not only does it reduce management (Rees and Paynter 1997). The was growing in riversand-based soil. The Plant Protection Quarterly Vol.15(4) 2000 157 Table 1. Conditions at the start of experiments set up at Krawarree and 1993. After six months grass was clipped Waterboard sites. The cover of native species excluded broom cover and to ground level leaving existing broom was from data collected at the first census on 6 December 1993 in seedlings intact. The age at first flowering of broom seedlings in these plots was undisturbed plots. Densities of broom and the broom seedbank are back- noted and compared to age at first flower- transformed means ± SE. ing in other cut treatments at the same site. Site Krawarree Krawarree Waterboard ‘improved’ ‘native’ Statistical analysis Data were analysed using the GLIM sta- % cover native species in herb layer 5% 71% 14% tistical package (McCullagh and Nelder Density of mature broom (m-2) 3.4 ± 1.4 10.0 ± 7.4 1.1 ± 0.8 1983) and followed the same procedure as Maximum age (years) of broom outlined in Paynter et al. (1998). Seedbank (by growth rings) 15 8–10 20–21 data for each core were Log (n+1) trans- Height of mature broom (cm) 249 ± 11 191 ± 8 238 ± 57 formed to normalize data prior to analy- Broom seeds under mature broom (m-2) 18524 ± 3162 3036 ± 1977 15675 ± 3756 sis. Broom seeds under immature broom (m-2) 2360 ± 1233 1500 ± 524 1569 ± 601 -2 Broom seeds 5 m from broom stand (m ) No plot used No plot used 39 ± 26 Results Conditions at the start of the experiment infested grassland was dominated by na- the start of the experiment in November (Table 1) showed that in the immature tives (mainly P. labillardieri, Carex 1993 and in November 1996. This sam- broom plots no plants had set seed sug- gaudichaudiana Kunth and M. stipoides) pling allowed assessment of the propor- gesting maximum age would not have ex- and mixed introduced perennial and an- tion of the autumn seedbank germinating ceeded five years. Mature broom density nual grasses. Three pairs of plots were also each autumn-spring. was highest in the Krawarree ‘native’ site used in (a) mature broom, (b) immature Detailed sampling of broom plots in and lowest at the Waterboard site, where broom and (c) 5 m out from the edge of the southern Australia was done in a compa- the mature broom had started to senesce. broom stand on the pasture side of the rable manner to experiments at the other Maximum recorded broom age reflected strip (Table 1). One plot in each pair was sites and conducted in two ways: this, the youngest broom being at the fenced as at Krawarree to keep out live- (a) Five random quadrats (0.5 × 0.5 m) Krawarree ‘native’ site thereby suggesting stock as well as resident rabbit, wombat were used in each of the experimental this was the site that had been invaded by and pig populations. subplots. For each quadrat the number broom most recently. Seedbank density of broom seedlings (with no woody was lowest at the site with the youngest Disturbance treatments parts), saplings (woody and 1+ year mature broom and highest at the The following disturbance treatments old), the approximate percentage cover Krawarree ‘improved’ site (Table 1). were randomly allocated to the three 5 × 5 of broom, native species, other exotic m subplots within each plot. In two sub- species, litter and bare ground were re- Seedbank dynamics plots all broom growing in or overhang- corded. Quadrats were re-randomized Change in the seedbank under mature ing the subplot was clipped or sawed to for each sampling date to give statisti- broom at Krawarree ‘improved’ and ‘na- ground level and the age of five of the cally independent samples across tive’, and at Waterboard are given in Fig- largest individuals was assessed from dates. ure 1 for the disturbed (cut only and cut growth rings. (b)In each experimental subplot, five per- and cultivated combined) and undis- (a) In one subplot the stumps were painted manent quadrats (also 0.5 × 0.5 m) were turbed plots. In undisturbed plots at each with Grazon® (active ingredients marked out using random co-ordinates site the average seedbank over four years triclopyr and picloram), otherwise after treatment allocation. Once broom was approximately 20 000 seeds m-2 at leaving the herb-layer undisturbed as plants were at least one-year-old sap- Krawarree ‘improved’ where the seed- might occur following natural stand lings, each plant was identified by a set bank remained quite steady, 6000 seeds senescence (‘cut’ treatment). of unique co-ordinates. Their heights m-2 at Krawarree ‘native’ where the (b)In the other subplot all broom stumps were measured at each sampling date. seedbank increased three-fold over the were removed and the ground manu- When the plants first flowered their four years and 15 000 seeds m-2 in the ally cultivated to 10 cm depth to resem- age was recorded. mixed grassland at Waterboard where the ble disturbance caused by pigs and Censusing was performed once in spring seedbank showed a three-fold decline wombats (‘cultivation’ treatment). (September–November), and autumn prior to the last sampling date. The high- (c) The third subplot was left untouched (March–June) and after each major rainfall est annual increment recorded in the as a control. event (>20 mm) in summer (November– seedbank was 5500 seed m-2 at the These treatments were identical in the ex- March). Censusing was not carried out Krawarree ‘native’ site 28 months after the periments in France and New Zealand, during droughts, i.e. 12–17 months after start of the experiment (summer 1995/96). with only treatment (a) being left out of the start of the experiment (summer 1994/ Seedbanks in disturbed plots (i.e. without the UK experiment (Paynter et al. 2000). 95), 28–30 months after the start of the ex- seed input) declined steadily during the Before allocating disturbance treat- periment (autumn 1996) and 44–54 course of the experiment at all sites giving ments, the number and heights of mature months after the start of the experiment an overall rate of decline of 36% per year. broom plants in each subplot were meas- (the El Niño drought from July 1997 to After four years seedbanks were half to ured and ten soil cores, 3.2 cm diameter May 1998). one order of magnitude lower across sites, and 10 cm depth, were taken from each by which time, regenerated broom was subplot (during November 1993). The Grass competition-free plots seeding in the plots. These changes did cores were sieved, hand-sorted and the To assess the effect of competition from not differ significantly between cut and number of seeds with fresh white endo- grass cover on broom seedling growth fol- cultivation treatments. sperm per core recorded. Soil cores were lowing disturbance treatments, a ‘cut’ then taken yearly at the annual maximum, treatment was imposed on two additional Recruitment from seed that is after seed fall and before autumn fenced 5 × 5 m subplots in mature broom Emergence of seedlings was observed in germination, except on two occasions at at Krawarree ‘improved’ in November all months but appeared to be linked to 158 Plant Protection Quarterly Vol.15(4) 2000

(a) Krawarree ‘improved’ 400 400 100 000 (a) (b) 300 300

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o

Seeds m o o 0 0 o 1000 1 1 61218 24 32 36 42 48 54 60 01224364860 61218 24 32 36 42 48 54 60 Time (months since start) Time (months since start)

Figure 1. Changes in number of Figure 2. Population curves for broom plants at Waterboard in broom plots broom seeds in the seedbank over for (a) fenced undisturbed, (b) unfenced undisturbed, (c) fenced cultivated, ▲ time in undisturbed (l, ,n) and (d) unfenced cultivated, (e) fenced cut and (f) unfenced cut subplots. ¡ q o disturbed ( , , ) broom plots Different shades are different cohorts. (mean ± SE). significant rainfall and daytime tempera- survival of different seedling tures of at least 15°C. Flushes of germina- cohorts in the different treat- 0.8 tion followed dry periods, particularly ments, in six mature broom 0.7 q droughts. For example, a 10 month subplots at Waterboard are 0.6 drought period in 1997/1998 (44–54 given in Figure 2. The patterns o months after the start of the experiment) observed at this site were typi- 0.5 o ¡ followed by rain led to the greatest flush cal of all sites except for fenced 0.4 (Figure 2) at all sites where seedling den- disturbed plots at Krawarree q -2 0.3 n sities reached 2500 m . The chance that a ‘improved’ which was the only ¡o l seed in the seedbank became a seedling site where rapid grass growth 0.2 q n n n o q o q l l lo ¡ also varied greatly between sites and led to decreasing success of 0.1 o n ¡ o n ▲n n loq o n l o o years (0.1% to 69%). This was not a func- later cohorts (data not shown). Proportion of the seedbank germinating ¡ l 0 l ¡ tion of whether broom overstorey was re- Waterboard (Figure 2) was also 0 1224364860 moved and/or soil was cultivated. The the most natural broom regen- Time (months since start) chance that a seed in the seedbank became eration site of the three as the a seedling was highest during the fourth existing mature broom stand Figure 3. Probability of seed in the seedbank year at all sites (Figure 3), the year after was already starting to senesce becoming a seedling against time at (a) the drought, suggesting that this propor- when the experiment was set ¡ tion was related to seasonal factors rather up. Broom saplings survived Krawarree ‘improved’ ( ,l), (b) Krawarree than local conditions. The exception to this under mature broom for up to ‘native (q,▲) and (c) Waterboard (o,n) both was grazing which tended to increase the three years. For the first five co- with (¡,q,o) and without (l,▲,n) grazing. chance a seed germinated into a seedling horts there was no significant (Figure 3). effect of cohort number on survival of autumn. Cohorts that geminated in later seedlings to three-year-old saplings (Fig- seasons are also showing similar survival Survival ure 4). Season of germination may not be levels (data not presented). Rainfall is Seedlings were divided into cohorts based important in seedling survival as these fairly aseasonal in the Shoalhaven valley on the date of first census. Patterns of five cohorts started in both summer and and may help explain seedling survival. Plant Protection Quarterly Vol.15(4) 2000 159 0.35 1000 There was an effect of site on 123rd year

12

0.3 percentage survival to three 12 124th year

12

years, being higher at Kra- 12 5th year 0.25 12 warree ‘improved’ (5.4% ± 2.1 12 100 12 0.2 (SE)) than at the other two sites 12

12 (0.64% ± 0.01; F2,31 = 13.3, 12 0.15 12 P<0.01). Cultivation (but not 12 0.1 12 the cut treatment) (F1,31 = 6.4, 12 123 10 12 123 12 123 0.05 P<0.05), grazing (F1,31 = 18.9, 123 12 123 Proportional survival after 3 years 12 123 P<0.001) and whether the seed- 12 12 123 0 12 12 123 lings were in immature broom 12 12 123 12 34 5 Log (number of flowering plants) 12 12 123 over mature broom (F = 23.5, 12 12 123 Cohort 1,31 12 12 123 1 P<0.001) increased sapling sur- Disturbed Control Disturbed Control Figure 4. Survival of the first five cohorts of vival over this time across all Fenced Unfenced broom seedlings (dates varied between sites), sites (Figure 5). for the first three years after germination, Figure 6. Number of flowering following application of disturbance Height and rate of regeneration plants in different age classes (third treatments (back transformed from arcsine to fifth year) at first flowering in transformed data) for the three sites; Height of three-year-old broom saplings (n = 585) was unaf- disturbed and control plots inside Krawarree ‘improved’ (white bars), Krawarree fected by cohort number or and outside fenced areas. Data from ‘native’ (striped bars) and Waterboard (black grazing although there were all sites. bars) ± SE. significant effects of site (F2,48 = 8.15, P<0.01), disturbance treat- dried too quickly for seedling establish-

(a) Grazing ment (F2,48 = 4.69, P<0.05), and ment (at Krawarree ‘native’). 0.04 whether the plots had mature or immature broom present Age at flowering

(F1,47 = 5.47, P<0.05; see Table 2). For broom plants that were followed, the 0.03 Three-year-old saplings were minimum age at which plants first flow- significantly shorter at the ered per subplot had a median and peak 0.02 Krawarree ‘native’ site, signifi- at four years, but varied between three cantly taller in immature broom and five years (Figure 6). Grazing and the 1234567 1234567 and significantly shorter in the presence of grass competition following 0.01 1234567 1234567 undisturbed control subplots. seedling establishment increased age at 1234567

1234567

Proportional survival after 3 years There were no significant flowering by at least a year, while distur- 0 1234567 Fenced Grazed height differences between the bance decreased age at flowering by at cut and cultivated treatments least a year. (b) Stand age (Table 2). 0.04 There were some marked lo- Discussion cal differences in rate of regen- Seedbanks 0.03 eration between treatments Changes in the seedbank under undis- across sites that must have re- turbed broom (Figure 1) suggested differ- flected local site conditions. For ent stages of stand development across 0.02 example, following a broom cut sites and this was supported by age of the or cultivation at Krawarree ‘im- oldest plants at each site. An increasing 0.01 1234567 1234567 proved’, regeneration without seedbank at Krawarree ‘native’ during

1234567

1234567 grazing was fastest following this study suggested that seedbank re-

1234567 Proportional survival after 3 years 0 1234567 cultivation in mature broom plenishment outweighed seed losses, Mature Immature subplots, while being fastest on while the senescent broom at Waterboard cut subplots in the immature failed to replenish its seedbank. A rela- (c) Disturbance treatment broom plots. Rapid growth of tively constant seedbank at Krawarree 0.08 exotic grasses slowed regenera- ‘improved’ over four years suggests this 0.07 tion in the cut plots under ma- site had seedbank replenishment match- 0.06 ture broom, while broom seed- ing seedbank losses, thereby indicating a 0.05 lings were probably already likely maximum to seedbank size. The present in the cut subplots un- peak recorded annual increments in the 0.04 der immature broom that could seedbank were of similar magnitude to 0.03 grow quickly following the cut. the inputs recorded in terms of a seed rain 0.02 Outside the fence, grazing of up to 8000 seeds m-2 (Hosking et al.

0.01 12345 12345 tended to nullify these differ- 1998). Rates of seedbank decline and the

12345 Proportional survival after 3 years 0 ences. In other mature broom final seedbanks after four years in dis- Cultivated Cut Under broom plots at Waterboard and Kra- turbed plots with mature broom over- Figure 5. Effect of treatment on survival of the warree ‘native’, regeneration storey removed were comparable to those was fastest in cut plots as re- from southern France (Paynter et al. 1998). first five cohorts of broom seedlings for the moval of vegetation cover ei- Censusing only three times a year and first three years after germination following ther caused the mobile sand to strategically following rain, detected most application of disturbance treatments (back bury the first few cohorts of peaks in seed germination, although seed- transformed from arcsine transformed data). seedlings (at Waterboard) or lings could have emerged and died unde- Mean data for all sites combined ±SE. exposed a shallow soil that tected between sampling dates. Despite 160 Plant Protection Quarterly Vol.15(4) 2000 Table 2. Cohort mean heights (cm) of three-year-old broom saplings across 1 given the observed average seedling sur- these sites in mature and immature broom in the three disturbance vival rates. This observation broadly treatments. Means calculated using heights of a total of 585 three-year-old agrees with field evidence that at least 25 saplings divided into a maximum of five cohorts for each site/treatment years of spraying broom in the one loca- tion has not been enough to prevent con- combination. See text for statistical analysis. tinued broom germination from the Site Krawarree ‘improved’ Krawarree ‘native’ Waterboard seedbank (Smith 2000). To hasten this Broom maturity Mature Immature Mature Immature Mature Immature process control strategies that impact di- rectly on the seedbank, for example fire Undisturbed 12 ± 8 37.8 0 5.7 ± 3 12 ± 2 34.5 ± 8 (see Downey 2000), should be considered Cut 33.1 ± 12 45.5 ± 10 9.2 ± 1.2 15.7 ± 9 56.2 ± 19 72.5 ± 26 for broom management in Australia. Cultivated 33.4 ± 14 54.2 ± 6 6.6 ± 4 10.9 ± 2 49.1 ± 11 60.5 ± 36 Our study also showed that any of the kinds of disturbance tested enhanced this deficiency the proportion of the effect on survival to three years old or broom survival. Even slashing mature seedbank which germinated in peak height reached by that age, which is prob- broom should therefore be recommended flushes was high and of comparable mag- ably equally true for survival to flowering only when combined with existing or nitude to the annual rate of seedbank de- (complete data not yet available). Cultiva- oversown competitive ground cover. At cline. This result suggests that most of the tion increased seedling survival to three- our study sites with moderate exposure to seedbank decline observed at sites with- year-old saplings and cultivation or cut- grazing animals and wombats, such expo- out seedbank replenishment (Figure 1), ting was necessary for survival beyond sure also increased the germination rate was likely to have been due to germina- three years in a mature broom stand, a re- and survival to three years, without any tion. Post-dispersal seed predation levels sult comparable to results from France negative impact on height gains of broom. observed, at least at Krawarree (Paynter et (Paynter et al. 1998). Cultivation resets the Although this exposure did slightly in- al. 1996), probably account for seed losses herb layer to zero cover, thereby allowing crease age at first flowering it did more prior to entering the seedbank. broom a greater chance of surviving than harm than good and should be avoided when it has to grow through an existing during the regeneration phase of broom. Recruitment from seed herb layer. Higher seedling survival to For broom management, exposure to Germination was not restricted to particu- three years in grazed plots may have been grazing may need to be restricted to ma- lar seasons as in the native range, a result due to grazing animals (mainly rabbits, ture plants (Sheppard et al. 2000). The common to many weeds in Australia kangaroos and cattle) removing much of great variation in response to fencing (Sheppard 2000) and results from aseason- the competing grass layer and reducing its across all sites shows that the type of ver- ality of rainfall. The proportion of the smothering capacity. Grazing was ob- tebrate herbivore involved will greatly in- seedbank that germinates was highly vari- served to have a significant negative effect fluence their impact (c.f. Paynter et al. able across seasons, as observed in France, on seedling survival in the UK experi- 2000). Restriction of access for those verte- but was generally higher on average in ment, but in the Australian experiment brates that are associated with broom Australia for any given germination co- grazing did not significantly reduce the stands in Australia, such as pigs and hort. For example the proportion of the height of three-year-old saplings, prob- wombats, is likely to be an important com- seedbank that germinates averaged about ably due to lower grazing intensity. In the ponent of any overall broom management 4% in France for the first three cohorts UK rabbit grazing intensity was consid- strategy. (data in Paynter et al. 1998), but 11% for ered to be very high (Paynter et al. 2000). Our study suggests broom may be the first three cohorts in Australia. This Site differences within Australia were evi- easier to control on sites with infertile or proportion represents about one tenth of dent in survival, being lower in sites with quick drying soils as at these sites survival the seedbank decay rate in France com- soils that appeared more prone to drying to three years was an order of a magnitude pared to a third of the seedbank decay rate (i.e. sandy soil at the Waterboard site and lower. Our preliminary observations also in Australia. While the proportion of the shallow soil at the Krawarree ‘native’ site) suggest that the time from disturbance to seedbank that germinated was correlated and height attained being lower in largely a new flowering infestation of broom will with March rainfall in France, in Australia native grassland. Broom survival and also be longer in such soils. Similarity in it appeared to be more related to the time height gains were greatest in immature age at first flowering across the distribu- since previous significant rainfall. This broom. tion of broom suggests that basic climatic proportion did not vary with disturbance Seedling survival to three years ap- factors such as temperature may have lit- treatment in this experiment. This differ- peared to be somewhat lower at our sites tle effect on speed of stand regeneration. ence contrasts with the results from the compared to the native range. For exam- Broom control is likely to be most effec- UK and France where disturbance pro- ple average survival following cultivation tive when the seedbank is low and com- moted germination of seed. An explana- across sites in Australia ranged from 21.4 petitive ground-cover high (i.e. when the tion for this result may be that the avail- to 2.1%, while average survival to three broom stand is still developing). If there is able competitive herb layer in undis- years of broom was c. 15 and c. 50% in an even-aged established broom stand al- turbed Australian plots was not sufficient France and the UK respectively (Paynter ready present, more effective control may to significantly suppress broom germina- et al. 1998, 2000). Average height at three be achieved if control measures are held tion rates. years was similar however between our back until the stand becomes naturally se- sites and the French site at about 40 cm nescent, as the seedbank may decline Survival and growth (Paynter et al. 1998). naturally during this stage. The most significant contrast between broom population dynamics in Australia Implications for management Acknowledgments compared with the native range (Paynter Seedbank survival data collected here sug- John Hosking, Jeremy Smith and Richard et al. 2000) was the survival and growth gest that at these sites it will take c. 11 Groves for critically reviewing this manu- rates of later cohorts of seedlings. In the years for an average seedbank under ma- script and John Hosking for assisting with native range, only the first cohort sur- ture broom to decay to a level where the the identification of some native species in vived to flowering and only following dis- chance of regenerating one three-year-old the plots. John Lester, Joel Armstrong and turbance. In Australia cohort age had no plant per square metre would be less than Paul Downey for assistance with data Plant Protection Quarterly Vol.15(4) 2000 161 collection and Anthony Swirepik and Noble, I.R. (1989). Attributes of invaders Rousseau, J. and Loiseau, A. (1982). Struc- Matthew Smyth who also helped with set- and the invading process: terrestrial ture et cycle de development des ting up the fenced and cleared plots. and vascular plants. In ‘Biological inva- peuplements a ‘Cytisus scoparius L.’ sions: a global perspective’, eds J.A. dans le chaine des puys. Acta Oecologia References Drake, H.A. Mooney, F. di Castri, R.H. Applicata 3, 155-68. Downey P. (2000) Broom and fire: man- Groves, F.J. Kruger, M. Rejmanek and Sheppard, A.W. (2000). Weed ecology and agement implications. Proceedings of M. Williamson, pp. 301-10. (J. Wiley & population dynamics. In ‘Australian the broom symposium held at Ellerston Sons, Chichester). weed management systems’, ed. B.M. and Moonan, 16–17 November 1998, Paynter, Q., Fowler, S.V., Hinz, H.L., Sindel, pp. 39-60. (R.G. and F.J. eds A.W. Sheppard and J.R. Hosking. Memmott, J., Shaw, R., Sheppard, A.W. Richardson, Melbourne). Plant Protection Quarterly 15, 178-83. and Syrett, P. (1996). Are seed-feeding Sheppard, A.W., Hosking, J.R. and Leys, Fowler, S.V., Harman, H.M., Memmott, J., insects of use for the biological control A.R. (2000). Broom (Cytisus scoparius Paynter, Q., Shaw, R., Sheppard, A. and of broom? Proceedings of the Ninth In- (L.) Link) population management Syrett, P. (1996). Comparing the popu- ternational Symposium on Biological strategies. Proceedings of the broom lation dynamics of broom, Cytisus sco- Control of Weeds, 21–26 January 1996, symposium held at Ellerston and parius, as a native plant in the UK and Stellenbosch, South Africa, eds C. Moonan, 16–17 November 1998, eds France, and as an invasive alien weed Moran and J. Hoffman, pp. 495-501. A.W. Sheppard and J.R. Hosking. Plant in Australia and New Zealand. Pro- (University of Cape Town, Cape Protection Quarterly 15, 134-9. ceedings of the Ninth International Town). Smith, J.M.B. (2000). An introduction to Symposium on Biological Control of Paynter, Q., Fowler, S.V., Memmott, J. the biogeography and ecology of Weeds, 21–26 January 1996, Stellen- and Sheppard, A.W. (1998). Factors broom (Cytisus scoparius) in Australia. bosch, South Africa, eds C. Moran and affecting the establishment of Cytisus Proceedings of the broom symposium J. Hoffman, pp. 19-26. (University of scoparius in southern France: implica- held at Ellerston and Moonan, 16–17 Cape Town, Cape Town). tions for managing both native and ex- November 1998, eds A.W. Sheppard Hosking, J.R., Smith, J.M.B. and Sheppard, otic populations. Journal of Applied Ecol- and J.R. Hosking. Plant Protection Quar- A.W. (1998). Cytisus scoparius (L.) Link ogy 35, 582-95. terly 15, 140-4. ssp. scoparius. In ‘The biology of Aus- Paynter, Q., Fowler, S.V., Memmott, J. Thompson, A.R. (1988). Fluroxypyr, a tralian weeds’. Vol. 2. eds F.D. Panetta, Shaw, R.H. and Sheppard, A.W. (2000). new herbicide for scrub and woody R.H. Groves and R.C.H. Shepherd, pp. Determinants of broom (Cytisus scopar- weed control in forestry and amenity 77-88. (R.G. and F.J. Richardson, Mel- ius (L.) Link) abundance in Europe. areas. Aspects of Applied Biology 16, bourne). Proceedings of the broom symposium 177-82. McCullagh, P and Nelder, J.A. (1983). held at Ellerston and Moonan, 16–17 Tutin, T.G., Heywood, V.H., Burges, N.A., ‘Generalized linear models’, 2nd edi- November 1998, eds A.W. Sheppard Moore, D.M., Valentine, D.H., Walters, tion. (Chapman and Hall, London). and J.R. Hosking. Plant Protection Quar- S.M., and Webb, D.A. (eds) (1968). Memmott, J., Fowler, S.V., Syrett, P. and terly 15, 149-55. ‘Flora Europaea’, Volume 2, p. 89. Hosking, J.R. (1993). What makes Rees, M. and Paynter, Q. (1997). Biological (Cambridge University Press, Cam- broom a major problem? Proceedings control of Scotch broom: modelling the bridge). of the Brighton Crop Protection Confer- determinants of abundance and the po- Waloff, N. and Richards, O.W. (1977). The ence, 22–25 November 1993, Brighton, tential impact of introduced insect her- effect of insect fauna on growth, mor- United Kingdom, pp. 753-8. (British bivores. Journal of Applied Ecology 34, tality and natality of broom, Saro- Crop Protection Council, Farnham, 1203-22. thamnus scoparius. Journal of Applied UK). Ecology 14, 787-98.

over 10 000 ha on the Tops. Broom is now estimated to cover about 2000 ha of the Controlling broom (Cytisus scoparius) in pasture on 4800 ha grazing property ‘Tomalla’, part the Barrington Tops – a graziers perspective of the larger Ellerston Pastoral Company. Seeds have been spread in several ways on ‘Tomalla’. They were carried on tracks A. Clark, Ellerston Pastoral Company, Ellerston via Scone, New South Wales of bulldozers during logging operations, 2337, Australia. on livestock and by water down creeks. Cattle have been observed reducing broom growth in young broom stands by Summary eating seedlings. This paper reviews Broom, Cytisus scoparius, is a major efforts on the Barrington Tops plateau. broom control options that have been tried weed on the property ‘Tomalla’, part of To date there has been no impact from on the property in recent years and dis- Ellerston Pastoral Company. Current biological control agents that have been cusses the success of these programs. broom control is by herbicides, fire and released on broom on the Barrington grazing. The effectiveness of these tech- Tops. Herbicides niques at ‘Tomalla’ is reviewed. Cost of On the property, broom is easily killed us- herbicide control of broom on ‘Tomalla’ Introduction ing the herbicide Garlon® (active ingredi- is currently around $45 000 per annum. Broom, Cytisus scoparius (L.) Link, was re- ent triclopyr, 170 mL to 100 L) when Additional resources have also been in- ported to have been introduced as a pot broom is in leaf and flower during the vested by the Company as a core partner plant to the property ‘Tomalla’ property months of October, November and De- in a biological control program initiated (1200–1317 m) on the Barrington Tops pla- cember. In other months diesel has been by the Broom Council. The council was teau in the 1840s (Waterhouse 1988). It has added to the mixture, but in the long term set up to coordinate broom control spread from ‘Tomalla’ to be a problem on this ends up being too costly. When 162 Plant Protection Quarterly Vol.15(4) 2000 herbicide is applied using a ‘handgun’ Livestock Biological control sprayer, the whole plant must be covered Goats In 1990 a need to coordinate broom con- otherwise it will regenerate from the Goats (a combination of feral nannies trol on ‘Tomalla’ and the adjoining State unsprayed portion. After successful from Cobar, New South Wales and male Forest and National Park led to the crea- spraying, dead branches of the plant must meat goats from Condobolin, New South tion of the Broom Council. One of the be destroyed, usually through burning, Wales) provide about the best form of con- main objectives of this council was to otherwise they help protect new broom trol using livestock as they eat smaller work towards the long term control of seedlings in the undergrowth and speed plants and ring-bark larger stems. Goats, broom through biological control agents up broom stand regeneration. however, seem to be more prone to toxins (Adams 2000). Ellerston Pastoral Com- On ‘Tomalla’ there are four main fac- in the weed than sheep and were difficult pany has been involved in this council and tors that prevent successful spraying: to contain within the control area. For ex- the Management Committee for the Bio- (a) Weather – with the high frequency of ample, during the 1980 drought the goat logical Control of Scotch Broom which rainfall and mist on the property it is herd escaped through holes in the fencing was set up following the commencement hard to find days suitable for spraying. caused by wombats and now lives as a of the biological control program. (b)Timber – trees and logs, in addition to feral population on the side of Sunny Brae Ellerston Pastoral Company, along with density of broom itself, make it hard to Hill. Here at least they are doing a good National Parks and Wildlife Service, State achieve an even spray cover of broom. job eating blackberries. Forests, NSW Agriculture and CSIRO, has (c) Rocks – the rocky terrain is not friendly contributed to the expense of the biologi- to spray vehicle gearboxes and differ- Sheep cal control campaign since its inception. entials causing frequent additional re- Sheep have been the main livestock used Three insects have been released for con- pair costs or preventing access to areas. to control broom and are quite effective. trol of broom on ‘Tomalla’. These insects (d)Wombat holes – these also damage the Sheep, especially crossbreeds, behave are the broom twigminer, Leucoptera suspension and chassis of spray vehi- similarly to goats, being also very difficult spartifoliella Hübner, a broom psyllid, cles and slow access to infested areas, to contain within the control area. In con- Arytainilla spartiophila Förster and a seed again making site access difficult. trast, merinos have less of a tendency to feeding bruchid, Bruchidius villosus Spray rigs used for herbicide application escape and are therefore more easily man- Fabricius. Only one insect, broom twig- to broom on ‘Tomalla’ include: (a) tractors aged. Up until the mid 1960s there were miner, has been seen following release on with spray tanks, (b) 4-wheel-drive trucks 3000 to 4000 sheep run on ‘Tomalla’ and, ‘Tomalla’ and no impact on broom has with spray tanks, (c) aerial spraying by with the use of fire, broom was well con- been achieved to date. Further releases helicopter (prior to restrictions on this tained. However, due to wild dog attack, will be made on ‘Tomalla’ in coming years form of control imposed in the 1980s), and sheep numbers have been reduced to and monitoring of releases and evaluation (d) manual cutting of bushes followed by about 1500 and these can only be run for of impact will no doubt continue. the spraying of stumps with Tordon® about 3 months a year until wild dogs find A scale insect, Parthenolecanium rufulum (active ingredients 2,4-D amine and them. At this time sheep need to be shifted (Cockerell), a native of Europe, occasion- picloram, applied undiluted). Chemical to lower country of Ellerston Pastoral ally kills branches and sometimes entire control of broom on ‘Tomalla’ is mainly Company. In 1985, 4000 sheep were run broom plants on ‘Tomalla’. It is not known for containment of existing infestations, for three months, November to January, in how this insect reached this area. control along access tracks and roads, and a 517 ha paddock called Hushes. They ate maintenance of previously sprayed areas. all the broom seedlings and the larger Conclusion Current chemical and labour costs of plants up to a height of 1.2 m. The follow- There is at present no effective cheap tech- spraying are approximately $45 000 per ing year seedlings reappeared all over the nique for control of broom on ‘Tomalla’. annum. paddock. The sheep had eaten the seeds Broom is being held in check by herbicides and effectively spread them in their drop- and grazing, but costs of control are too Fire pings. In 1986 and each year since, 1500 expensive to attempt broom control Fire is one of the most economic ways of sheep were returned to the paddock in throughout the entire 2000 ha infestation. controlling broom on ‘Tomalla’. The main November for four months. When possi- disadvantage of this control technique is ble the area is now burnt off which also References that it stimulates germination of broom kills plants that have been damaged by Adams, B. (2000). Raising awareness of seeds. Since frequent use of fertilizer on sheep. There is some evidence from this the broom (Cytisus scoparius) problem grazing land from the late 1950s, however, that livestock and fire can be effectively on the Barrington Tops. Proceedings of general farm management practise has used in combination. the broom symposium held at Ellerston frowned upon fire, as it tends to deplete and Moonan, 16–17 November 1998, soil sulphur levels, thereby reducing effec- Cattle eds A.W. Sheppard and J.R. Hosking. tiveness of fertilizer applications. Since the During a drought a large area of broom in Plant Protection Quarterly 15, 139-40. 1980s, fire was reintroduced as a scrub one part of Hushes paddock was sprayed Waterhouse, B.M. (1988). Broom (Cytisus control technique, but there are very few with molasses. Cattle were introduced scoparius) at Barrington Tops, New days suitable for burning at ‘Tomalla’, and into the paddock where they broke down South Wales. Australian Geographical the majority of these fall in periods when bushes to get to the foliage and this also Studies 26, 239-48. a total fire ban has been imposed else- allowed sheep to clean up seedlings. This where in the region! novel use of cattle with sheep may also have wider application. Plant Protection Quarterly Vol.15(4) 2000 163 internal minimum of 25 measure trees (i.e. perimeter trees acted as buffers). The Broom (Cytisus scoparius (L.) Link) competition and above ground biomass of broom (kg ha-1 management in eucalypt tree farms dry matter (DM)) was determined by ran- domly selecting six 1 m2 quadrats from both inter- and intra-rows. C.D. Barnes and G.K. Holz, North Forest Products, PO Box 63, Ridgley, Tree heights and DBH (diameter at Tasmania 7321, Australia. breast height i.e. 1.3 m) were measured at trial establishment (1997) and again in June 1998 and 1999. This data was ana- Summary lysed using analysis of variance. Results A trial to evaluate competitive impact of broom control and fertilizer treatments are presented as incremental stem volume broom (Cytisus scoparius (L.) Link) on was established in a three year old E. calculated as the difference between vol- establishing Eucalyptus nitens (H.Deane nitens plantation. ume in 1999 and 1997, i.e. & Maiden) Maiden was established in a In order to assess significance of the height × DBH2 × π two year old plantation with a uniform broom threat, affected areas were identi- Stem volume = broom cover, near Waratah, north-west fied in a broom mapping program linked 12 Tasmania. Treatments consisted of three to a Geographical Information System levels of broom control (total, inter-row (GIS). The many benefits of using GIS for Management of broom and none), combined with two levels of weed management planning have been Broom was mapped in the north-west of fertilizer (0 and 200 kg ha-1 nitrogen). Af- reviewed by Prather and Callihan (1993). Tasmania, focusing on the Surrey Hills es- ter one and a half years the current prac- The GIS software (ArcView) graphically tate south of Burnie using the Tasmanian tice of inter-row broom control without positions map features in relation to Weed Mapping Guidelines (Bishop 1997). added nitrogen had no significant im- known locations, and relates these fea- Mapping was concentrated on those areas pact on E. nitens stem volume. There was tures to other cartographic features. susceptible to infestation, or where broom a significant increase in stem volume of was known to occur, rather than picking at least 23% due to nitrogen and of 49% Materials and methods sites at random. The location (Australian increase due to total broom control. This Competition trial Grid Map Coordinates), land use and ten- suggested that competition was likely to The trial was established on an ex-native ure, dimensions of infestation, plant size be for nutrients and that it would be forest site near Waratah in north-west and signs of management were manually more economic for plantation managers Tasmania. Soils at the site were developed recorded and entered into a database. The to apply 200 kg ha-1 nitrogen at years two on basalt (ferrosol) with soil pH around data was processed by ArcView GIS soft- to three than to perform post-plant inter- 5.2. The average annual temperature is ware. row broom control. 8°C. The average annual rainfall of 2199 Mapping of broom in the north-west mm (decile one = 1748 mm per annum, Results and discussion of Tasmania revealed 59 250 ha contain- decile nine = 2675 mm per annum) is dis- Competition trial ing broom. Data generated during map- tributed throughout the year with a Biomass measurements indicated there ping was used to develop a broom man- marked winter peak. Rainfall for the pe- were similar amounts of broom on the in- agement plan that includes control of riod from trial establishment (December tra-rows (16 050 kg ha-1) and inter-rows isolated broom plants, isolation of large 1997) to the most recent measurements (16 300 kg ha-1), confirming observations infestations and adoption of long term (June 1999), was 3399 mm, while evapora- that broom was evenly distributed across control strategies such as release of bio- tion for the same period was 1287 mm. the plantation. logical control agents. Following harvesting in 1993, the site As shown in Figure 1 the addition of was disced then mounded using a Savan- fertilizer significantly increased the DBH Introduction nah mound plough. E. nitens were planted increment from 1997 to 1999 (P=0.0001). Broom (Cytisus scoparius (L.) Link) is a po- at a spacing of 3.5 × 2.6 m in October 1995 Total broom control had a significant im- tential threat to the success of eucalypt tree giving a planting density of approxi- pact on DBH increment (P=0.0001), but farms in north-west Tasmania. Anecdotal mately 1100 seedlings per hectare. The site inter-row broom control had no signifi- evidence suggests that broom competes has a uniform broom cover with few other cant impact (P=0.61). strongly with developing Eucalyptus weeds present. Incremental gain in tree height aver- nitens (H.Deane & Maiden), resulting in Trial design was a randomized com- aged 216.9 cm ± 19.9 cm for the 18 months reduced tree growth with longer rotation plete block with four replicates, three lev- and was not significantly influenced by ages and fewer trees surviving to matu- els of broom control (total, inter-row and broom control (P=0.86) or fertilizer treat- rity. Three years after planting Richardson none) and two levels of nitrogen fertilizer ment (P=0.84). et al. (1996) found a 51% reduction in Pinus (0 and 200 kg ha-1 nitrogen). Inter-row Incremental gain in stem volume for 18 radiata D.Don stem volumes when grown broom control represents approximately months after the treatments were applied in the presence of broom. However, there 35% of the plantation area. Broom control is shown in Figure 2. Total broom control, are no references on the impact of broom was performed initially using brush- with or without fertilizer resulted in a 49% competition on developing eucalypts. cutters, with all slashed broom left on site. increase in stem volume (P=0.0001) com- Broom is currently controlled in plan- Glyphosate was applied to broom re- pared with the control. Fertilizer re- tations through combinations of inter-row growth using a shielded nozzle knapsack sponses with inter-row or no broom con- tractor mounted slashing and shielded at 1350 g active ingredient ha-1 three trol were around 24% (P=0.0038). There spraying with glyphosate. Since these months after brushcutting. An organo- was no response to inter-row broom con- costs are incurred in years two to three of silicant penetrant was included at 0.2% trol alone (P=0.54). an on average fifteen year rotation, it is v/v. Urea was applied after the initial As total broom control is expensive essential that these operations provide op- broom control treatments as a spot appli- (~$400-$500 ha-1) the current practice on timal tree productivity gains. To evaluate cation at the base of each tree. broom infested sites is to inter-row slash competitive impact of broom in young Plots were approximately six tree rows and apply glyphosate (i.e. IRBC and E. nitens a trial consisting of post-plant wide by eight trees long, providing an NFER) to control regrowth (~$180 ha-1). 164 Plant Protection Quarterly Vol.15(4) 2000 ) 3 Incremental Stem Volume (cm

Figure 2. Effect of broom control and fertilizer treatment on incremental stem volume after 18 months (standard error = 771). Percent figures represent increase in volume compared with the control. (TBC = total broom control, IRBC = inter-row broom control, NBC = no broom control. FERT = spot application of nitrogen (200 kg ha-1), NFER = no fertilizer).

broom control. Nambiar and Management of broom Sands (1993), suggest that on The survey identified approximately Figure 1. Effect of broom control (standard sites where moisture is not lim- 59 250 ha infested with broom. error = 0.36) and fertilizer treatment (standard iting, such as at Waratah, the Broom maps (Figure 3) were used to error = 0.37) on incremental DBH (diameter at effect of controlling competi- develop a management plan aimed at con- breast height) after 18 months. (TBC = total tors in improving nutrient sup- trol of isolated plants close to North Forest ply is equalled to that of apply- Products land, management of larger in- broom control, IRBC = inter-row broom ing large amounts of fertilizer. festations and encouragement of biologi- control, NBC = no broom control. FERT = spot Considering an estimate of ni- cal control measures. A key to the strategy -1 application of nitrogen (200 kg ha ), NFER = trogen content in broom shoots is to manage spread of major infestations no fertilizer). (1.45%) by Wheeler et al. (1987) through cultural practices. Moving ma- and the biomass of broom on chines from infested broom sites spreads site (~16 240 kg ha-1) there is a broom seed. Identifying these sites and After 18 months this had no significant potential input of 235 kg ha-1 nitrogen at implementing a wash down procedure impact on eucalypt growth (6% increase). this site from total broom control. It may should limit future broom seed spread. A cheaper, more effective option is to spot be that we can achieve equivalent growth Across the larger broom infested areas, apply 200 kg ha-1 nitrogen (i.e. NBC and responses to total broom control simply biological control agents, provided by the FERT) at the base of each tree (~$140 ha-1). through the addition of higher rates of ni- Management Committee for the Biological On many sites access for fertilizing is diffi- trogen. Control of Scotch Broom through the Co- cult, and work is currently being under- As broom is intolerant of shade operative Research Centre (CRC) for taken to assess the relative merits of spot (Hosking et al. 1998), the key to managing Weed Management Systems are being re- versus broadcast (e.g. aerial) fertilizer ap- broom in plantations is to achieve canopy leased. It is envisaged this long term con- plication. closure at the earliest possible age. Appli- trol strategy, rather than chemical control, Mechanisms of competition at this site cation of nitrogen at years two to three can will be successful in significantly reducing are unclear. It can be assumed with high help achieve this. the broom population in the mapped area. annual rainfall that moisture is not a ma- jor limiting factor to growth. At trial estab- lishment the eucalypt canopy was above that of broom, which would suggest com- petition for light is not limiting tree growth, although there maybe some effect on the lower canopy. Response of eucalypts to nitrogen in the no broom control treatment shows that soil nitrogen is limiting tree growth at this site. Rhizobial nodules on broom roots fix nitrogen, but compared to other agricul- tural legumes the rate of nitrogen produc- tion is low (Wheeler et al. 1979, cited in Hosking et al. 1998). In controlling broom there would be an increased level of min- eralization and nutrient uptake by euca- Figure 3. Locations of known broom infestations on and around Surrey lypts possibly explaining the lack of re- Hills, Tasmania (scale of North West Coast 1:50 000). NFP = North Forests sponse to nitrogen associated with total Products. Plant Protection Quarterly Vol.15(4) 2000 165 Acknowledgments References Prather, T.S. and Callihan, R.H. (1993). The authors wish to thank John Hosking Bishop, A. (1997). ‘Tasmanian weed map- Weed eradication using geographic in- (NSW Agriculture and CRC for Weed ping guidelines’, 2nd edition. (Tasma- formation systems. Weed Technology 7, Management Systems) and Andy nian Weed Mapping Network, Devon- 265-9. Sheppard (CSIRO Entomology and CRC port). Richardson, B., Vanner, J.R., Davenhill, D. for Weed Management Systems) for their Hosking, J.R., Smith, J.M.B. and Sheppard, and Coker, G. (1996). Mechanisms of continued support and helpful discussion A.W. (1998). Cytisus scoparius (L.) Link Pinus radiata growth suppression by on broom management in Tasmania. We ssp. scoparius. In ‘The biology of Aus- some common forest weed species. New would also like to thank Terry Williams tralian weeds’. Volume 2, eds F.D. Zealand Journal of Forestry Science 26, and Bruce Fielding of North Eucalypt Panetta, R.H. Groves and R.C.H. Shep- 421-37. Technologies for their help in mapping herd, pp. 77-88. (R. G. and F. J. Richard- Wheeler, C.T., Helgerson, O.T., Perry, broom, and Jeremy Wilson and Ashley son, Melbourne). D.A. and Gordon, J.C. (1987). Nitrogen Goldstraw of North Forest Products for Nambiar, E.K.S. and Sands, R. (1993). fixation and biomass accumulation in their support with GIS software. Competition for water and nutrients in plant communities dominated by forests. Canadian Journal of Forestry Re- Cytisus scoparius L. in Oregon and Scot- search 23, 1955-68. land. Journal of Applied Ecology 24, 231-7.

As a part of public forest management, access is also provided for recreational Controlling broom (Cytisus scoparius (L.) Link) in traffic, particularly 4-wheel-drive enthusi- native forest ecosystems asts. This development contributed to spread of broom along fire trails in the

A B area. Broom infestations also cause other K. Carter and A. Signor management problems. Feral pigs favour A State Forests of New South Wales, Manning Region, PO Box 392, Taree, New dense broom clumps (some up to 1 km2 in South Wales 2430, Australia. Current address: NSW National Parks and size) and this makes pig control more dif- Wildife Service, 78 Hargreaves Drive, Taree, New South Wales 2430, ficult. In turn, pig diggings create a seed- Australia. bed for new broom, and pigs are believed B State Forests of New South Wales, Gloucester, PO Box 1, Gloucester, New to transport seed in mud attached to them. South Wales 2422, Australia. Current address: NSW Agriculture, RMB 944, Watercourses are another important vec- Tamworth, New South Wales 2340, Australia. tor of broom seeds. Control techniques Control programs commenced in ear- Summary nest in the late 1970s using hand slashing From State Forests of New South Wales broom on the Barrington Tops in State and some chemical spraying. Early work perspective the major broom infestation Forests, a National Park and on private trialed hand slashing, then heaping the is on Barrington Tops – covering over property. slash over the site and burning it when 10 000 ha of State Forest, National Park Broom seems to mainly occupy areas of dry. Achieving a satisfactory burn is a real and private land. The use of State Forests open forest and woodland with a snow- problem in this sub-alpine environment. on Barrington Tops as a case study soon grass (Poa sieberiana Spreng.) understorey. With an intense fire, a very good kill was explains the frustration of dealing with These areas tend to be mostly non-com- achieved and some seed was incinerated. this environmental weed in forest eco- mercial forests and therefore the impact of The downfall was an excellent seedbed for systems. Adequate access for ground broom on forestry of commercial native remaining seed, resulting in very dense techniques like slashing and spraying is species is largely untested in terms of com- regeneration of broom within 12 months. a major issue in its control. mercial timber production. Given the lati- Given that broom may produce seed tude of Barrington Tops, broom, by de- within 2–3 years of germination, spraying Introduction fault, occupies the highest altitudes due to of broom regeneration was mandatory On Barrington Tops, the broom (Cytisus its preference for cool climates. It is feared within that time. Obviously this produced scoparius (L.) Link) infestation possibly (but not proven) that broom on the an exponential increase in sites to be started as early as the 1840s as an im- Barrington Tops may develop the capac- treated i.e. maintenance of previously ported garden and hedge plant ity to encroach on areas of lower altitude sprayed areas plus any new areas. Control (Waterhouse 1988). Much of the broom in- over time through natural selection proc- requirements using these methods grew fested forest land on the Barrington Tops esses. This possibility is suggested by the beyond the capacity of available re- was vacant crown land until dedication as occasional observation of short-lived indi- sources. Accessibility of broom infested State Forests and National Park from the vidual broom plants along watercourses areas was also a problem. It became in- early 1960s through to early 1970s. Access at lower altitudes than the main infesta- creasingly obvious that alternative meth- to the high country (over 1000 m above sea tion. ods of control were needed, the most level) where broom occurs awaited State Broom has infiltrated some forest log- likely being long-term control using bio- Forests of New South Wales (SFNSW) ging areas adjacent to the woodlands – logical agents. road construction programs from 1968- mainly in Eucalyptus fastigata H.Deane & Spraying with Garlon® (active ingredi- 1978. It is perceived by some that broom Maiden, E. obliqua L’Hér. and E. dalrymple- ent triclopyr, 170 mL to 100 L) is very ef- spread also coincided with displacement ana Maiden ecotones and may well inter- fective, but expensive and labour inten- of graziers’ seasonal burning of the fere with commercial Eucalyptus regenera- sive. The spray program has concentrated Barrington Tops high country. There is tion by rapidly occupying the site. No for- on preventing linear expansion of the now over 10 000 ha of land infested with mal studies have been done. broom infestation along fire trails, by 166 Plant Protection Quarterly Vol.15(4) 2000 destruction of broom plants in new loca- during the flowering season when it is enterprise in NSW, rather broom is an tions, as well as by providing a buffer be- very distinctive. The mapping work has environmental weed that needs to be tween seed bearing broom plants and the shown that spread of broom in the last controlled to ensure aesthetic value of trails. This has been quite successful, but three years has not been as dramatic as these areas and to protect native bio- again requires annual maintenance of re- some initially expected. diversity, and State Forests is committed generating broom given the many years to carry out control measures as a respon- that seed remains viable (Hosking et al. Cost-benefit assessment sible land management agency. The only 1998). The quandary with ongoing or ex- The current State Forests broom control sensible solution to broom control in such panded herbicide use is that all past and budget is around $30 000–40 000 per an- extensive native forest ecosystems with present efforts will be to no avail if the num. SFNSW has also contributed to the poor general access lies in biological con- program is discontinued and broom re- current biological control programs with trol with other control methods dovetailed generation occurs. The program is also contributions of between $5000 and into an integrated program across the en- limited in success due to the need to con- $41 500 per annum from 1989 to 1998. tire landscape, independent of tenure. The tain the movement of broom occurring Overall, the physical control measures immediate, if sidestepping, solution for away from trail edges, i.e. beyond the carried out by SFNSW over the past 20 SFNSW to most of the Barrington Tops spray hose length of about 100 m. Beyond years have managed to reduce linear broom problem has recently been deliv- this distance access is a problem requiring spread of broom along trails. However, ered by the NSW Government transfer of installation of spray tracks where possible the above mapping has clearly identified these impacted State Forest lands to the (using machinery) if control using herbi- more rapid linear spread of broom along NSW National Parks and Wildlife Service cide is desired. water courses. as part of the establishment of a ‘Compre- Quarantine controls are implemented hensive, Adequate and Representative Re- where logging occurs alongside broom in- Other SFNSW infestations serve System’ – complete with broom! fested areas. This is costly to industry and Other infestations on State Forest land oc- SFNSW will continue to apply control SFNSW, but is seen as a necessary meas- cur in areas of native vegetation and pine methods for broom in the balance of its ure. Quarantine measures mainly involve forest within the central tablelands pine estate but this is considered to be rela- washing down machinery and trucks, as plantations at Sunny Corner State Forest tively minor with a fair chance of eradica- they leave infested areas, to remove mud and in Gemalla State Forest, areas to the tion from State Forest land, provided that containing broom seeds. east of Bathurst. Here there is over 40 ha adequate resources are focused on that of broom, and like the Barrington Tops in- area. Mapping broom festation, the weed is of concern for its en- Accurate mapping of broom commenced vironmental effects rather than any sig- References in 1982 using aerial photographs. In 1995 nificant commercial effect. The Sunny Hosking, J.R., Smith, J.M.B. and Sheppard, mapping was conducted using a helicop- Corner infestation is encroaching on the A.W. (1998). Cytisus scoparius (L.) Link ter mounted Global Positioning System habitat of the endangered Bathurst copper ssp. scoparius. In ‘The biology of Aus- ‘live linked’ to a Geographic Information butterfly (Paralucia spinifera Edwards and tralian weeds’ Volume 2, eds F.D. System on a lap-top computer. Mapping Common). Control measures in this area Panetta, R.H. Groves and R.C.H. Shep- using this technology was carried out are mostly through use of herbicide and herd, pp. 77-88. (R.G. and F.J. again in 1998 as a cooperative exercise be- mechanical removal to assist in regenera- Richardson, Melbourne). tween State Forests and the NSW National tion of the host plant of this butterfly, na- Waterhouse, B.M. (1988). Broom (Cytisus Parks and Wildlife Service. It has supple- tive blackthorn (Bursaria spinosa Cav.). scoparius) at Barrington Tops, New mented mapping work carried out either South Wales. Australian Geographical from the ground or from aerial photo- Conclusion Studies 26, 239-48. graphs. Broom mapping is made particu- Broom appears to have no real impact on larly easy from the air or from photos the commerciality of any State Forests Plant Protection Quarterly Vol.15(4) 2000 167 briar (Rosa rubiginosa L.) infestations re- spectively. As broom may defoliate after Herbicides for broom (Cytisus scoparius (L.) Link): flowering, it was considered appropriate testing alternatives to Grazon® to compare results with the addition of a wetting agent that may assist herbicide absorption into woody photosynthetic Craig Hore, Alpine National Park, Parks Victoria, PO Box 20, Bright, Victoria branches. A relatively high application 3741, Australia. rate of 0.2% of the wetting agent BS1000 was used to qualitatively assess impor- tance of its inclusion. Roundup Biactive Summary was applied on 13 May 1997, and Grazon® is registered for control of however, Grazon cannot be used in close Roundup was applied on 14 May 1997. broom (Cytisus scoparius) and is used proximity to crops (such as grapes and to- Both applications were made in the after- widely by Parks Victoria. Because of its bacco), waterways or residential areas. An noon. Prevailing weather conditions were volatility, however, Grazon cannot be alternative registered herbicide for broom calm, fine and sunny, daily maximum used in close proximity to crops (such as that can be used in such situations is re- temperatures were 17 and 18°C respec- grapes or tobacco), waterways and resi- quired. This paper describes field trials tively, following frosty nights. dential areas. An alternative registered that were conducted to determine the ef- herbicide for broom that can be used in fectiveness of Roundup® and Roundup Second trial such situations was required. This paper Biactive® (called Biactive in the tables) The second trial was conducted on 4 De- describes field trials that were conducted (Monsanto; active ingredient glyphosate). cember 1997. In this trial additives, the to determine effectiveness of Roundup® wetting agent, BS1000, and the penetrant, and Roundup Biactive®. As a result of Methods Pulse®, were compared, as the latter is this study Roundup and Roundup A trial area was located near the Bright known to enhance absorption of herbi- Biactive have been registered for control Recreation Reserve. This area was divided cide, particularly by non-foliar areas of the of broom. into discrete broom plots. Each plot con- plant. Treatments were applied as in Ta- tained broom plants of variable age, in- ble 2 to seven plots. Prevailing weather Introduction cluding both isolated plants and dense conditions were calm, sunny and the ex- Broom (Cytisus scoparius (L.) Link) is a se- thickets, and was of a size (10 × 10 m ) to ternal temperature was 26°C. rious environmental weed in Victoria’s justify a tank mix volume (40–50 L) that Alpine National Park and surrounding ar- would be representative of normal work- Results and discussion eas. Communities where it poses a serious ing rates. The treatments applied in the tri- First trial threat include the Bogong High Plains and als are described in Table 1. A slip-on Assessment was made on 20 November other subalpine areas up to 1700 m above spray unit with a single hand-gun was 1997. Observations (Table 1), made inde- sea level. Many river systems sourced used to apply herbicide with a spray gun pendently by several trained personnel, from these catchment areas, such as the pressure of 180 psi. suggested that greater success had been Mitta Mitta and Snowy River systems are achieved using the 2.9% glyphosate appli- lightly to seriously infested. The herbi- First trial cation rates (plots 2, 3 and 5). Nonetheless cide, Grazon® (DowElanco; active ingredi- Two application rates, 1.3% and 2.9% ac- significant success was achieved by 1.3% ents triclopyr and picloram) is registered tive ingredient were used. Based on other glyphosate application rates particularly for broom control and is used widely weed control treatments, application rates considering the late application. The addi- by Parks Victoria and the Department selected were those recommended for 2 m tion of wetting agent was determined to of Natural Resources and Environment tall blackberry (Rubus fruticosus L. species be advantageous. The results from this (DNRE). Because of its volatility, aggregate) infestations and 1.5 m sweet trial prompted the second.

Table 1. Results of glyphosate spray trials on broom. Plot Herbicide Wetting agent Volume Shoot Comments Type % active Type % wetting applied brownout ingredient agent (L) (%) Trial 1A 1.1 Biactive 1.3 nil 40 >90 1.2 Biactive 2.9 nil 50 >90 1.3 Roundup 1.3 nil 40 >90 1.4 Roundup 2.9 nil 40 >90 1.5 Roundup 2.9 BS1000 0.2 40 >90 1.6 Roundup 1.3 BS1000 0.2 40 >90 Trial 2B 2.1 Roundup 1.3 BS1000 0.1 50 85–90 Possibly due to insufficient coverage. Smaller bushes 100% 2.2 Biactive 1.3 BS1000 0.1 50 100 2.3 Biactive 1.3 nil 50 100 2.4 Biactive 2.9 nil 50 100 2.5 Roundup 1.3 nil 50 100 2 small plants 40% due to insufficient coverage 2.6 Biactive 1.3 Pulse 0.2 50 100 1 large bush 60% due to insufficient coverage 2.7 Roundup 1.3 Pulse 0.2 50 100 Montpellier broom (Genista monspessulana (L.) L.A.S. Johnson) also present (also 100% brownout) A Herbicide applied 13 and 14 May 1997, assessment made 20 November 1997. B Herbicide applied 4 December 1997, assessment made 4 June 1998. 168 Plant Protection Quarterly Vol.15(4) 2000 Second trial Table 2. Relative cost of mixed herbicide. Assessment was made on 4 June 1998. The Herbicide Cost (20 L) Application rate Cost (100 L of mix) results are presented in Table 1. Results overall were a good kill where sufficient Grazon $660 250 mL / 100 L $8.25 coverage was achieved during spraying. Biactive $133 1.3 L /100 L $8.65 Any differences between Roundup or A The advice provided in this document is intended as a source of information only. Roundup Biactive, or the value of using Always read the label before using any of the products mentioned. The author accepts various additives in the spray mix, could no responsibility or liability whatsoever for any loss or damage arising from using the not be defined given the application rates above products used.

Herbicide selectivity The possibility of non-target damage is a and potential contamination of water- Satisfactory results were obtained at the key criteria in herbicide selection. courses. 1.3% application rates if applications were Roundup and Roundup Biactive are non- made during periods of active broom selective herbicides. The possibility of the Registration for label use growth. With this application rate, wet- understorey surrounding the weed spe- The results were sufficient to start the reg- ting agent or penetrant additives gave no cies being affected is high, particularly istration process for Roundup and additional benefit. Further trials may grass species. Similarly, with Grazon (a Roundup Biactive against broom. Lack of show that lower application rates are also selective herbicide for woody weed con- this registration did not prevent Parks Vic- effective during active growth and that trol), the possibility of nearby woody spe- toria from using Roundup for broom con- additives may contribute to the level of cies being affected is high. The legal use of trol in National Parks, as the agency is al- control at such levels. While applications herbicides near watercourses is covered lowed to use herbicides at label rates for at the 2.9% rate gave control during early by label registration. There is worldwide the control of off-label species provided winter periods, when the plant was not concern regarding the effects that Parks Victoria management agrees. Off- actively growing, application at that time surfactants have on amphibians. Most label recommendations, however, cannot is not recommended as applications are herbicides either contain surfactants or re- be made to the public until the herbicide is most economically made when the quire their addition during mixing, to en- registered. This places the agency in an amount of active ingredient applied is hance adherence and absorption. awkward position, when undertaking minimal.A Roundup Biactive (apparently ‘surfactant- control operations in conjunction with free’) is claimed to be safe for use in and neighbouring landholders. Legislation in Acknowledgments around watercourses in certain situations. Victoria does allow for training and certi- Steve Chaffey (Field Representative, Despite this, the application method fication of DNRE staff to provide off-label Monsanto) and Keith Fallow (Business should be designed to minimize the advice. These considerations are now aca- Manager, Monsanto) for discussions on amount of spray actually entering any demic as Roundup and Roundup Biactive trial protocols, assistance with assessment water. were registered for broom control in of effectiveness and for support to obtain March 2000 and this use will appear on registration of Roundup and Roundup Relative costs future labels. Biactive for use against broom. Ian Walton Relative costs are remarkably close (Table (Catchment Management Officer DNRE 2). Factors affecting herbicide choice that Conclusions Myrtleford) for assistance in the assess- should be considered, prior to cost consid- These trials have shown that glyphosate is ment of the first trial and assistance on the erations, are potential non-target damage an effective herbicide for broom control. second trial. Plant Protection Quarterly Vol.15(4) 2000 169 The broom containment program is re- vised and implemented on an annual ba- Controlling broom (Cytisus scoparius (L.) Link) in sis. Current control techniques have natural ecosystems in Barrington Tops National Park evolved to minimize environmental im- pact. Since implementation of the contain-

A B ment program in the late 1980s broom has Mellesa Schroder and Chris Howard been successfully contained along con- A National Parks and Wildlife Service, Hunter Region, Locked Bag 99, Nelson tainment lines within the National Park, Bay, New South Wales 2315, Australia. however this has not prevented an in- B Barrington Tops National Park, National Parks and Wildlife Service, PO Box crease in density of broom within the 236, Gloucester, New South Wales 2422, Australia. main infestation. The containment pro- gram has been successful in treating iso- lated infestations and protecting unaf- Summary fected catchments. Isolated broom plants In 1996 the New South Wales National established in woodlands and open forest in the Gloucester Tops area subalpine en- Parks and Wildlife Service (NPWS) de- dominated by Eucalyptus pauciflora Sieber vironment (separated from the infested veloped a formal management strategy ex Spreng. with occurrences of other spe- area on the Barrington Tops by a forested for broom containment in Barrington cies such as E. stellulata Sieber ex DC. and area at slightly lower altitude) have been Tops National Park. This strategy was E. dalrympleana Maiden (NPWS 1989). removed as part of this program. based on a review of the 1987 contain- Since the 1980s broom has also began to When the containment strategy was ment strategy developed by the NPWS in infest both the edge of subalpine wetlands implemented it was recognized that the association with the Broom Council. The and the open plains of the plateau (M. only long term solution to reducing the strategy recognizes the impact of broom Newton personal communication). Veg- size of the main infestation appeared to be on the natural ecosystem and aims to en- etation communities below the Barrington establishment of suitable biological con- sure annual implementation of an effec- Tops plateau within the National Park are trol agents. The Broom Council in the tive containment program without com- dominated by subtropical rainforest, 1980s campaigned for funding to under- promising natural values of the area by warm temperate rainforest, beech forest take research into biological control causing further impacts on this sensitive (Nothofagus moorei (F.Muell.) Krasser) and (Adams 2000). subalpine environment. wet and dry sclerophyll forests. Whilst rainforests do not provide conditions suit- Broom management strategy for Introduction able for the establishment of broom, large Barrington Tops National Park Broom (Cytisus scoparius (L.) Link) has be- disturbed areas and drainage lines within The NPWS is developing control strate- come a major weed on the Barrington rainforests, where there is more light, may gies for all major weeds in National Parks Tops plateau (including Barrington Tops provide suitable conditions. Dry sclero- across New South Wales. In 1996 the National Park) since it was first intro- phyll forests at high altitude also provide NPWS developed a ‘Scotch Broom Man- duced as a garden plant on the property suitable open conditions for broom estab- agement Strategy’ which includes an an- ‘Tomalla’, at the northern end of the pla- lishment. nual works program based on the original teau, in the 1840s. Broom was recognized Broom control was initiated as early as containment program. No review had as a major weed by 1964 and its spread 1972 in Barrington Tops National Park. been undertaken since the original con- was associated with grazing, fire and log- Experimental plots were established to tainment program was developed in 1987 ging trails throughout the plateau (Water- trial various control methods including and the annual works program had suf- house 1988). clearing, fire and a range of chemicals (M. fered from limited resources. Barrington Tops National Park con- Newton personal communication). Early The strategy was developed to ensure serves about 80 000 hectares of rugged control methods involved large scale her- an integrated approach to containing the landscapes varying in altitude from 1585 bicide spraying. This method was largely infestation. The strategy incorporates the m above sea level (asl) on the Barrington ineffective as it involved a high degree of following objectives: Tops plateau down to 170 m asl at Chich- disturbance to native vegetation and soils 1. Contain and treat broom within the ester Dam. This large altitudinal range which in turn promoted broom seed ger- existing infestation. Broom is control- combined with a mosaic of geology, soils, mination. There were also concerns about led along roadways, walking tracks rainfall and aspects provide a diversity of the safety of spray operators using such and recreational areas to minimize vegetation communities and faunal habi- large amounts of herbicides. spread into non-infested area. The tats. Vegetation communities grade from As a result of unsuccessful control tech- boundaries of the infestation are also subtropical rainforests and tall open for- niques the Broom Council was formed in treated biennially. These boundaries ests in the valleys through to cool temper- 1987. The council recognized that the dis- are either road edges or natural ate rainforests and subalpine woodlands tribution and ecology of broom did not al- boundaries such as rainforest. Recently and wetlands on the plateau (the latter low for its total eradication (Howard broom control has commenced in areas two are impacted by broom). Rainforests 1995). In 1987 a containment strategy was identified as containing threatened of Barrington Tops National Park are the developed between affected landholders, plant species. southern limit of World Heritage listed including New South Wales National 2. Identify and treat any isolated infes- rainforests of eastern Australia. The di- Parks and Wildlife Service (NPWS), State tations outside the main infestation. verse vegetation communities found Forests of New South Wales (SF NSW) Isolated infestations are identified by a in the park provide habitat for over 60 and private landholders. The aim of the biennial aerial survey and subse- rare or threatened plant and animal spe- strategy was to protect non-infested quently treated. Previously treated in- cies. subalpine and lower catchment areas and festations are mapped and monitored Broom infests an estimated 10 000 minimize broom spread from the main in- biennially. hectares of the Barrington Tops and is festation. In addition the NPWS has a re- 3. A monitoring program. Aims to: having a major impact on the natural ecol- sponsibility to contain broom in a way (a) identify isolated infestations, ogy of the subalpine environment (Water- that minimizes further environmental im- (b) measure changes in the density and house 1988, Smith 1994). This weed is pacts. distribution of the main infestation, 170 Plant Protection Quarterly Vol.15(4) 2000 (c) measure success of the annual con- The cut and paint technique minimizes Current treatment techniques have tainment program, soil disturbance reducing potential broom limitations and the cost of physical re- (d) monitor impact and spread of bio- seed germination. Physical removal re- moval and chemical application on such a logical control agents. duces impact to non-target species and grand scale (even for containment only) is 4. Co-ordination of management with protects water quality and aquatic fauna. high. Table 1 shows the cost of broom and adjoining landholders. As part of the containment strategy within associated control measures since 1985. 5. Provide community information and the main infestation herbicide spraying Considering the seed longevity and the awareness. using triclopyr is undertaken along verges quantity of soil stored seed (Hosking et al. 6. Support the biological control pro- of vehicle trails and walking trails. Treat- 1998) containment alone must continue to gram. Participate in the release of bio- ment extends 10–20 m from the road edge. protect subalpine areas outside the main logical control agents and implement Treatment of trails reduces seed spread to infestation and sensitive communities suitable monitoring programs. other areas by vehicles, walkers and ani- within the main infestation. This contain- 7. Identify the resources required to im- mals. Some of the treated areas along trail ment program also involves control of ver- plement the management strategy an- edges have become refuges for native tebrate pests. Dense broom thickets pro- nually. An annual works program has plant species including rare and threat- vide shelter for feral animals (Parsons and been developed for objectives 1 and 2. ened plants. Triclopyr is used, as it is not Cuthbertson 1992) such as pigs and foxes. This provides a detailed account of the detrimental to Poa sieberiana Spreng. var. The annual pig control program reduces location of treatment areas and appro- sieberiana which is the dominant ground- soil disturbance and potential movement priate control techniques. cover, thus protecting the soil from distur- of broom seed by pigs. bance. Other non-target species, particu- Biological control of broom is integral Control techniques larly rare plants can be at risk from herbi- to the longer-term containment program. Three control techniques are used during cides if applied indiscriminately (Heinrich Three biological control agents have been the annual program from October to Janu- and Dowling 1998, 2000). Staff and con- released in locations throughout the ary these include: tractors are being trained to identify rec- Barrington Tops plateau, Leucoptera 1. physical removal of immature broom, ognizable rare plant populations and less spartifoliella (Hübner) (twig mining moth), 2. cut and paint technique (stems are cut obvious ones are tagged to avoid herbi- Artainilla spartiophila (Förster) (a broom and neat glyphosate is applied), cide application to broom plants within psyllid) and Bruchidius villosus Fabricius 3. herbicide spraying. the vicinity. These broom plants are re- (seed feeding bruchid). Release sites have High costs are associated with physical moved either physically or by using the been recorded and impact and spread of removal and the cut and paint technique cut and paint technique. agents from these sites is being monitored. because they are labour intensive. There- The herbicide, triclopyr, is sprayed Once numbers build up a planned and fore these techniques are only employed from vehicle mounted rigs but is not used systematic approach to their redistribu- on isolated plants, small infestations or in near waterways, or in wetlands, in the tion is anticipated. the following areas: area because of potential impact to aquatic (a) where some populations of threatened ecosystems. All staff and contractors are Monitoring of the broom infestation plants are located, trained in appropriate use of herbicides to Previous ad hoc monitoring of the broom (b)along the edge of water ways and in decrease potential ecological impacts from infestation has indicated the need for a co- the subalpine wetlands, herbicide use. ordinated and consistent approach in the (c) in and around recreational areas.

Table 1. Expenses associated with broom control in Barrington Tops National Park from 1985 to 1999. Program 1985/ 1986/ 1987/ 1988/ 1989/ 1990/ 1991/ 1992/ 1993/ 1994/ 1995/ 1996/ 1997/ 1998/ 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996A 1997 1998 1999 NPWS labour / administration 15 000 15 000 18 000 20 000 22 000 25 000 20 000 15 000 15 000 5 000 5 000 4 000 4 000 5 000 Broom spraying (temporary labour) 2 500 3 500 4 000 5 000 5 000 3 000 Broom spraying (contract labour) 6 000 8 000 25 000 30 000 35 000 Broom physical removal 6 000 10 000 20 000 Herbicide and materials 7 000 11 500 13 000 16 000 10 000 6 000 4 500 5 500 4 000 4 500 5 000 12 000 12 000 10 000 Pig control staff and materials 3 000 3 000 4 000 4 000 4 000 4 000 5 000 4 000 4 000 5 000 7 000 10 000 7 000 7 000 Biological control program 25 000 25 000 27 000 33 000 33 000 27 000 27 000 25 000 20 000 Rare and threatened plant survey 30 000 Aerial survey (by helicopter) 2 000 2 000 Mapping of main infestation 20 000 Total 27 500 33 000 39 000 45 000 41 000 63 000 54 500 51 500 56 000 53 500 52 000 86 000 118 000 119 000 A In 1996 the Barrington Tops National Park received new additions which included 1000 hectares of crown land infested with broom. As a result of this new land resources were increased to support the Scotch Broom Management Strategy. Plant Protection Quarterly Vol.15(4) 2000 171 future. The two main infestations were Many of these species utilize the sub al- within the wetlands and along the edges first mapped by NPWS in 1988 from 1982 pine woodlands and wetlands. of rivers (M. Newton personal communi- aerial photographs. In 1989 SF NSW pro- Fauna species listed on the Threatened cation). Wetlands of high ecological duced maps showing the density (i.e. infill Species Conservation Act 1995 and known significance are being prioritized for within the infestations) from 1987 aerial to occur within Barrington Tops National physical broom removal. photographs. In 1992/3 SF NSW mapped Park and likely to occur on the plateau are: Since the 1970s fire on the plateau has the perimeter of the broom infestations. been largely restricted. Prior to this time, This map indicated a slight increase in the Birds low intensity summer burns associated area of the main infestations from 1987. Powerful owl with cattle grazing were common (NPWS Broom densities have only been recorded Ninox strenua (Gould) 1989). Broom infestation has resulted in on one occasion, therefore density Masked owl increased soil moisture levels (Water- changes within the main infestation are Tyto novaehollandiae (Stephens) house 1988) and a lack of ground cover. currently unknown. Additional aerial sur- Sooty owl There are now very few days where con- veys of the boundary of the broom infesta- Tyto tenebricosa (Gould) ditions are dry enough to carry fire result- tion were undertaken in 1996 and 1998 Rufous scrub-bird ing in a decline in fire events. Further re- with particular emphasis on locating iso- Atrichornis rufescens (Ramsay) search is required to gain an understand- lated infestations for on-ground treat- Painted snipe ing of fire ecology on the Barrington Tops ment. Aerial photographic runs were Rostratula benghalensis (Linnaeus) plateau and potential changes to fire ecol- completed in December 1998. Aerial pho- Glossy black-cockatoo ogy due to broom infestations. tographic interpretation (API) has re- Calyptorhynchus lathami (Temminck) cently been undertaken and will provide Olive whistler Research information regarding the rate of spread Pachycephala olivacea Vigors & There have been various research projects and densities. This information will be Horsfield undertaken on broom on the Barrington compared with the 1989 maps. Tops. More information, however, is re- Mammals quired to improve overall management of Threatened species and other Spotted-tailed quoll the broom infestations particularly in ref- environmental impacts Dasyurus maculatus (Kerr) erence to the ecology of species native to Broom is causing major ecological Parma wallaby the Barrington Tops plateau. The authors changes to the natural environment of the Macropus parma Waterhouse consider further research would be valu- Barrington Tops plateau (Waterhouse Broad-toothed rat able on: 1988, Smith 1994). The subalpine natural Mastacomys fuscus Thomas (a) impact of broom on threatened species, environment of Barrington Tops National Brush-tailed phascogale (b)impact of broom on the fire ecology of Park provides habitat for a range of threat- Phascogale tapoatata (F.A.Meyer) the Barrington Tops plateau, ened species. In 1997 the NPWS employed Koala (c) relationship between broom and intro- consultants to undertake a rare plant sur- Phascolarctos cinerus (Goldfuss) duced vertebrate pests, vey of the plateau area (Heinrich and Eastern freetail-bat (d)changes in broom density within the Dowling 1998). Although the survey had Mormopterus norfolkensis (J.E.Gray) main infestation, limitations it was designed to identify the Eastern false Pipistrelle (e) changes to the soil profile in areas of location, abundance and provide further Falsistrellus tasmaniensis (Gould) infestation, information on rare or threatened plants Common bent-winged bat (f) impact of broom on subalpine wet- likely to occur within the broom infesta- Miniopterus schreibersii (Kuhl) lands, waterways and open plains. tions. The information gained has been in- Little bentwing bat valuable in assisting with the protection of Miniopterus australis (Tomes) Future broom management those species. Distribution records from Yellow-bellied sheathtail-bat Broom containment forms just part of the the survey are being used to assist in tar- Saccolaimus flaviventris (Peters) annual operational management of geting broom control. Greater broad-nosed bat Barrington Tops National Park, which In total, 28 species of rare or threatened Scoteanax rueppellii (Peters) also includes management of feral ani- plants have been identified within the mals, fire, recreational use as well as natu- main broom infestations of the Barrington Amphibians ral and cultural resources. Part of the Tops plateau (Heinrich and Dowling Glandular frog success of the broom containment pro- 1998). Of these, four are listed as vulner- Litoria subglandulosa Tylers & Anstis gram has been due to ongoing communi- able under the New South Wales Threat- Stuttering frog cation with surrounding landholders ened Species Act 1995 and seventeen (in- Mixophyes balbus Straughan to ensure a coordinated program. The cluding the four vulnerable species) are NPWS is committed to a regional/catch- listed as rare or poorly known in Briggs In the case of the broad-toothed rat, broom ment approach to pest management (Leys and Leigh (1996). Five possible new spe- is invading the edges of the subalpine 1998). cies of orchids were also discovered in the wetlands, outcompeting grasses such as P. As land managers the NPWS have a re- 1998 survey (Heinrich and Dowling 1998). sieberiana var. sieberiana which are an im- sponsibility to continue to implement con- The study highlighted the importance of portant shelter and food source for the rat. tainment programs that will not compro- the Barrington Tops plateau for rare, Further research on the plateau is required mise existing natural ecosystems. NPWS threatened and endemic plant species and to determine the distribution of threat- will continue environmental assessment indicated the need for further survey ened fauna species and the potential im- of control techniques. The broom infesta- work to be undertaken. For more informa- pact of broom upon them. tion is likely to expand unless the contain- tion on rare and threatened plant species The wetlands within the subalpine area ment program is successful. The success of of the Barrington Tops see Heinrich and feed six river systems. Use of herbicides this program is reviewed annually. Dowling (2000). for broom control within wetlands and The program will continue to prevent Twenty seven species of threatened along waterways is unacceptable because infestation of unaffected catchments and fauna (NPWS Wildlife Atlas 1999) occur of potential impacts on aquatic flora and subalpine environments. NPWS also aims within Barrington Tops National Park. fauna. Broom is becoming more common to protect sensitive communities within 172 Plant Protection Quarterly Vol.15(4) 2000 the main infestation by using an inte- Strategy to include new areas of the Na- ssp. scoparius. In ‘The biology of Aus- grated management strategy. In addition tional Park. tralian weeds’ Volume 2, eds F.D. to the containment program, effective Panetta, R.H. Groves and R.C.H. monitoring and continued research are an References Shepherd, pp. 77-88. (R.G. and F.J. integral component of managing broom in Adams, B. (2000). Raising awareness of Richardson, Melbourne). the future. The use of biological control the broom (Cytisus scoparius (L.) Link) Howard, C. (1995). Hunter District Sub- agents is regarded as the only economic problem on the Barrington Tops. Pro- mission to the Wilderness Assessment long-term method of reducing the size of ceedings of the broom symposium held Report for Barrington Tops. Unpub- the main broom infestations. A planned at Ellerston and Moonan, 16–17 No- lished report. systematic redistribution program for bio- vember 1998, eds A.W. Sheppard and Leys, A. (1998). NSW National Parks and logical control agents will be undertaken J.R. Hosking. Plant Protection Quarterly Wildlife Service Summary of Pest Man- in collaboration with researchers once 15, 139-40. agement Programs 1997/98. Unpub- numbers of agents build up. Briggs, J.D. and Leigh, J.H. (1996). ‘Rare or lished. threatened Australian plants’. (CSIRO NPWS (1989). Draft plan of management Acknowledgments Publishing, Melbourne). of Barrington Tops National Park, New We would like to thank M. Newton, Sen- Heinrich, A. and Dowling, B. (1998). Rare South Wales National Parks and Wild- ior Field Supervisor, NPWS, for informa- and threatened plant survey of life Service, Raymond Terrace office of tion on broom control on the Barrington Barrington Tops National Park - pla- NPWS. Tops. He has been involved with broom teau area. Unpublished report pre- NPWS (1999). The NSW National Parks control in Barrington Tops National Park pared for the NSW National Parks and and Wildlife Atlas database, CD ROM. since the 1970s. Wildlife Service. Parsons, W.T. and Cuthbertson, E.G. Heinrich, A. and Dowling, B. (2000). (1992). ‘Noxious weeds of Australia’. Postscript Threats to the rare and threatened plant (Inkata Press, Melbourne and Sydney). In March 1999 the Barrington Tops Na- species of the Barrington Tops. Pro- Smith, J.M.B. (1994). The changing eco- tional Park was expanded to include areas ceedings of the broom symposium held logical impact of broom (Cytisus scopar- of Barrington Tops State Forest and at Ellerston and Moonan, 16–17 No- ius) at Barrington Tops, New South Polblue Crown Land Reserve. The NPWS vember 1998, eds A.W. Sheppard and Wales. Plant Protection Quarterly 9, 6-11. are now responsible for management of J.R. Hosking. Plant Protection Quarterly Waterhouse, B.M. (1988). Broom (Cytisus most of the broom infestations occurring 15, 172-6. scoparius) at Barrington Tops, New on community lands. The NPWS is cur- Hosking, J.R., Smith, J.M.B. and Sheppard, South Wales. Australian Geographical rently reviewing the 1996 Management A.W. (1998). Cytisus scoparius (L.) Link Studies 26, 239-48.

extensive areas of almost treeless, wet Threats to the rare and threatened plant species of heath and sedgelands occurring in drain- age depressions of both Barrington and Barrington Tops Gloucester Tops. These areas are often very open and therefore exposed to dry- Anne HeinrichA and Bill DowlingB ing winds, ice and snow. Some wetlands A 389 Playfords Road, Comboyne, New South Wales 2429, Australia. were more protected from the extreme weather conditions as they occur between B PO Box 197, Dungog, New South Wales 2420, Australia. wooded areas e.g. Little Murray wetland. Mean annual rainfall over Barrington Tops and Gloucester Tops is approxi- Summary mately 1470–1700 mm (CMPS&F Environ- Future management of rare and threat- State Forests and private land should mental 1995). Some areas on the escarp- ened plant species in the Barrington place high priority on the protection of ment side receive higher rainfall than ar- Tops National Park on the Barrington the whole subalpine habitat as well as eas further north-west, away from the es- and Gloucester Tops plateau is depend- populations of rare plants by focusing carpment (CMPS&F Environmental 1995). ent upon knowledge of their locations, funding priorities to reduce these Mean annual temperature is about 9°C abundance and threats to their survival. threats. (Tweedie 1963). A literature and field survey was carried According to Veness and Associates out in summer 1997–98 and further field Introduction (1995) the two parent rock types on the surveys in summer 1998–99 and spring The plateau in the Barrington Tops Na- plateau area are granodiorite and tertiary 1999. Surveys found that 30 species of tional Park covers an area of 11 000 ha and basalt. Resulting soils are friable with scat- rare or threatened plants, 18 of which are is dominated by subalpine woodland tered stones. Granodiorite soils consist of possibly endemic, are likely to occur, or where the major tree species is Eucalyptus a dark reddish brown, silty clay loam A are known to occur, on the plateau area pauciflora Sieber ex Spreng. interspersed horizon while basalt topsoils are charac- of Barrington Tops and Gloucester Tops. with Eucalyptus stellulata Sieber ex DC., terized by strong pedal layers of a very Nine possible new species, all Orchid- Eucalyptus dalrympleana Maiden and Euca- reddish brown, subplastic, silty clay loam. aceae, were located during the literature lyptus fastigata H.Deane & Maiden. In ad- The A2 horizon in basalt areas consists of and field surveys. Populations of rare dition the plateau has an extensive system a dark reddish brown, silty clay or is and threatened plants were found both of subalpine wetlands and patches of cool unbleached (Veness and Associates 1995). in the National Park and in forestry land. temperate rainforest dominated by Much of the 11 000 hectares in the Na- Threats include further spread of broom Nothofagus moorei (F.Muell.) Krasser up to tional Park and extensive areas outside the (Cytisus scoparius), spread of other 1550 m above sea level (asl). Park are affected to varying degrees by weeds, feral pigs, recreational use and A considerable part of the plateau is broom (Cytisus scoparius (L.) Link subsp. fire. Managers of the National Park, occupied by subalpine wetlands which are scoparius) which has the potential to Plant Protection Quarterly Vol.15(4) 2000 173 reduce the available habitat for rare or subsampled in several random plateau could have an adverse impact on threatened plant species. The Gloucester quadrats (10 × 10 m). the rare plants as this is a serious pest in Tops (c. 1000 hectares) has no known • The location of broom plants within 50 similar climatic areas in the southern ta- broom infestations. A broom management m of the rare plant population at risk blelands of New South Wales. This threat strategy has been prepared to contain was recorded. to rare plants would be similar to broom broom within affected catchments using • Signs of potential threats were noted except that the seeds of blackberry are annually applied control measures along e.g. access, feral animal activity, fire. spread by birds and mammals present on roadways and at the boundaries of the in- Sites were only surveyed once or twice the plateau. festation. There are also management given the size of the survey areas so some strategies to control other weeds, to better terrestrial orchids and annual plants 5. Rare plant populations not adequately manage recreational usage and fire and to would have been missed. conserved. The largest population of control feral animals. However in order to Identities of all rare and unknown Corybas sp. A so far located on the protect rare and threatened plant plants were confirmed by voucher speci- Barrington Tops and another smaller one populations, their locations, abundance men sent to Sydney or Canberra. Plant remain outside reserves on Barrington and threats to their survival needed to be names follow Harden (1990–1993), except Tops. This orchid is however reserved at determined. where there have been more recent revi- Ben Halls Gap National Park. Similarly Surveys for rare and threatened plant sions. Chiloglottis platyptera has a large popula- species were carried out on the Barrington tion in a forestry area surrounded by log- Tops (1350–1585 m asl) and Gloucester Results ging activities and is present in Ben Halls Tops (1140–1300 m asl) plateau in the Na- Rare and threatened plants located on the Gap National Park. Populations of tional Park, State Forests and private land plateau Grevillea granulifera and Pterostylis sp. D ensuring coverage of all the different plant A list of rare and threatened plants on the were found at only one unreserved site. communities. plateau of Barrington and/or Gloucester Before the survey documented here, Tops and their status is given in Table 1. Discussion botanical surveys of the Barrington Tops The plateau of Barrington Tops and and Gloucester Tops plateau although Potential threats to rare and threatened Gloucester Tops appears to be a centre of quite extensive in their coverage had very plants endemicity as well as providing suitable few details on rare and threatened species 1. Broom. Broom has altered grassland subalpine habitat for many other rare and (Fraser and Vickery 1938a,b, Mort 1983, and woodland understorey habitats of threatened plants. Such plants occurred in Adam 1987). One survey of State Forests most of the rare plants by shading out her- all habitats of the plateau. However, con- (Binns 1995), did identify a number of rare baceous plant species. Nearly all rare and centrations of these plants occurred in or and threatened plants as did the New threatened plant populations on Barring- near the edges of the subalpine wetlands South Wales north east forest biodiversity ton Tops have been affected to some de- and along creeks on the Barrington Tops study (NPWS 1995). Other recent surveys gree by either individual broom plants or and Gloucester Tops plateau. have usually been of short duration, of thickets of broom. Table 1 gives an indica- Broom appears to be the major threat to only accessible areas and by botanists in- tion of the percentage of rare plant the rare and threatened plants on the terested in one group of plants (e.g. the populations within 50 m of broom. Some Barrington Tops plateau. Populations of Orchidaceae). rare plant habitat has probably already plants which appear to be most threatened been lost to broom. Broom also provides by broom include: Chionogentias barring- Methods shelter for feral pigs. tonensis, Diuris venosa, Microtis sp. aff. rara, Field searches for each rare or threatened Like broom one of the rare plants, Plantago cladarophylla, Plantago palustris, plant were made based on priority areas Ozothamnus sp. 1, appeared to re-colonize Prasophyllum rogersii, Pterostylis sp. aff. i.e. known locations and habitats obtained disturbed areas especially along the edges cycnocephala, Prasophyllum sp. aff. fuscum, during the literature search and following of tracks but broom had not yet reached Prasophyllum sp. aff. odoratum and consultation with National Parks and the main population of Ozothamnus sp.1. Tasmannia glaucifolia. Broom increases Wildlife Service staff. Various sources shading and leads to high litter accumula- were used, including scientific journals, 2. Feral pigs. Feral pigs turned over soil in tion as well as competing for growth sites. previously collected specimens at the Na- many places. Sods of snowgrass (Poa Smith (1994) found that common plants tional Herbarium of New South Wales sieberiana Spreng.) were often completely typical of well-lit snowgrass grassland on and from people with specific knowledge. turned over as though a plough had Barrington Tops neither remained nor be- Transects within the priority areas worked the area, often in the vicinity of came frequent as broom plants aged. were surveyed by walking many kilome- the rare Orchidaceae, suggesting their diet Many of the plants identified in this report tres through the selected vegetation com- includes orchid tubers. Pigs also dig out occupy grassland habitats and would munities. These included: the edges of large wallows in peaty soils at the edges probably be similarly affected. Studies of wetlands, wetlands, open grassland, of the wetlands which is part of the habi- individual rare plant populations may be woodland and forest. Rare plant informa- tat of Chionogentias barringtonensis, Corybas required to determine how long they can tion was gathered within 20 m of the sp. A, Euphrasia ciliolata, Microtis sp. aff. survive with broom invasion of their habi- transects. If a rare plant population was rara, Plantago cladarophylla, Plantago tat. For example how long will terrestrial located the area searched was extended at palustris, Prasophyllum sp. aff. odoratum, orchids survive in the shade of broom? each site using the following guidelines Prasophyllum rogersii and Pterostylis sp. D. Can Ozothamnus sp. 1 survive competition (adapted from the National Resources with broom seedlings for newly disturbed Audit Council significant plant project 3. Recreational use. Many of the rare sites? (NPWS 1995)). plants were found in or near frequently Management of broom on the Barring- When a rare plant was found: used picnic or camping areas. Such sites ton Tops plateau should be given high • Small populations were counted by were associated with large areas of regen- priority in areas in and around the searching along parallel lines and tem- erating broom. subalpine wetlands, creeks and rivers. It is porarily marking plants to avoid dou- also important to reduce broom spread ble counting. 4. Other weeds. Blackberry (Rubus along trails and from the edge of existing • Large or widespread populations were fruticosus L. complex) also present on the infestations. Biological control of broom is 174 Plant Protection Quarterly Vol.15(4) 2000 Table 1. Vulnerable, rare, poorly known and significant plant species identified on the Barrington Tops or Gloucester Tops plateau during the survey or in consultation with David L. Jones, Centre for Plant Biodiversity Research, Australian National Herbarium, Canberra. The ROTAP code (Appendix A has the ROTAP Conservation Code) and Risk Code (under the New South Wales Threatened Species Conservation Act), plant population distribution status and the percentage of known rare plant populations within 50 m of broom plants are noted. Name of taxa Family ROTAP (Appendix A)/ Plant population % of known Risk Code distribution populations on plateau within 50 m (reference) of broom Category –Vulnerable Diuris venosa Rupp Orchidaceae 2VC Schedule 2 Disjunct (13) 100 Pterostylis sp. D Orchidaceae 3VCa Schedule 2 Endemic (13) 40 Tasmannia glaucifolia J.B. Williams Winteraceae 3VCi Schedule 2 Disjunct (3) 80 Tasmannia purpurascens (Vickery) A.C.Sm. Winteraceae 2VC-t Schedule 2 Disjunct (3) 50 Category – Rare Acacia barringtonensis Tindale Fabaceae 3RCa Disjunct (4) 40 (Mimosoideae) Chiloglottis palachila D.L. Jones Orchidaceae 3RC- Disjunct (5) 0 Chionogentias barringtonensis L.G. Adams Gentianaceae 2RC- Endemic (6) 100 Corybas sp. A Orchidaceae 2RC- Disjunct (13,15) 30 Chiloglottis sphyrnoides D.L. Jones Orchidaceae 3KC- 0 Leptospermum argenteum Joy Thomps. Myrtaceae 2RC- Endemic (8) 80 Plantago cladarophylla Plantaginaceae 2RC- Endemic (9) 80 B.G. Briggs, Carolin & Pulley Plantago palustris L.R. Fraser & Vickery Plantaginaceae 2RC- Endemic (9) 90 Poorly known Chiloglottis platyptera D.L. Jones Orchidaceae 2KC- Disjunct (5) 0 Euphrasia ciliolata W.R. Barker Scrophulariaceae 2KC- Endemic (10) 64 Ozothamnus sp. 1 Asteraceae 2KC-t Endemic (11) 33 Grevillea granulifera Proteaceae 3KC- Disjunct (12) 0 (McGill.) P. M. Olde & N. Marriott Pterostylis elegans D.L. Jones Orchidaceae 2KC Altitudinal 0 range extension to 1530 m (1, 14) Significant taxa / no ROTAP codes Prasophyllum sp. aff. fuscumA Orchidaceae ?Endemic (1) 100 Prasophyllum sp. aff. odoratumA Orchidaceae ?Endemic (1) 50

Prasophyllum rogersii Rupp Orchidaceae Endemic (1) 100 Microtis sp. aff. raraA Orchidaceae ?Endemic (1) 100 Chiloglottis sp. aff. pluricallata Orchidaceae Disjunct (5) not known Orthoceras strictum forma viride Orchidaceae Very rarely seen (1) 0 Pterostylis sp. aff. cycnocephalaA Orchidaceae ?Endemic (1) 100 Pterostylis sp. aff. parvifloraA Orchidaceae ?Endemic (13) 30 Pterostylis sp. aff. longifoliaA Orchidaceae Range extension (13) 0 Pterostylis sp. aff. monticolaA Orchidaceae Endemic (13) 0 Caladenia sp. aff. carneaA Orchidaceae Disjunct (13) 0 Caladenia sp. aff. patersoniiA Orchidaceae ?Endemic (13) not known A Possible new species. References (1) pers. comm. D.L. Jones 1998 (2) D.L. Jones pers. comm. in Binns 1995 (3) Harden 1990 (4) Binns 1995 (5) Bishop 1996 (6) Adams 1995 (7) Jones 1993 (8) Thompson and Logan 1991 (9) Briggs 1992 (10) Barker 1992 (11) pers. comm. C. Puttock 1998 (12) Olde and Marriott 1994 (13) pers. comm. D.L. Jones 1999 (14) Jones 1997 (15) pers. comm. J.R. Hosking 1999 desirable as other control measures are native plant communities. The impact of and flowering periods of these species. more likely to damage native plants. It broom spraying on Chionogentias Feral pig control should also be a prior- was observed during the present surveys barringtonensis, Euphrasia ciliolata and ter- ity as they often concentrate their activi- that broom spraying had at least tempo- restrial orchids (for example Diuris venosa, ties in and around the wetlands where a rarily affected some Tasmannia purpur- Microtis sp. aff. rara, Pterostylis sp. aff. number of the rare plants were affected. ascens and Tasmannia glaucifolia bushes. cycnocephala, Prasophyllum sp. aff. fuscum, Feral horses appeared to be too few to be Damage was possibly caused by spray Pterostylis sp. aff. parviflora, Pterostylis sp. having an impact on the rare or threatened drift, though localized damage will need aff. patersonii) may be more harmful, as plants. However, their numbers should to be tolerated given the overall benefit to spraying coincides with the vegetative not increase as this may add to the impact Plant Protection Quarterly Vol.15(4) 2000 175 Appendix A. ROTAP Conservation Code. Puttock, Centre for Plant Biodiversity Re- search, Canberra; Gwen Harden, Curator, Conservation Code (Briggs and Leigh 1996) National Herbarium of New South Wales, Distribution Category (can be 1, 2 or 3) Royal Botanic Gardens, Sydney; Doug 1. Known by one collection only Binns, Research Division, State Forests of 2. Geographic range in Australia less than 100 km NSW; Hunter District and Northern Zone 3. Geographic range in Australia greater than 100 km staff, National Parks and Wildlife Service The Conservation Status (can be X, E, V, R, or K) and Wayne Burns, artist, Dungog. X Presumed Extinct: taxon not collected or otherwise verified over the past 50 years The 1997–1998 literature and field sur- despite thorough searching in all known and likely habitats, or of which all known vey was funded by the New South Wales wild populations have been destroyed more recently. National Parks and Wildlife Service. As- E Endangered: taxon in serious risk of disappearing from the wild within 10–20 years sistance in the field was given by Harold if present land use and other threats continue to operate. This category includes taxa Ralston. with populations possibly too small (usually less than 100 individuals) to ensure sur- vival even if present in proclaimed reserves. References V Vulnerable: taxon not presently endangered , but at risk over a longer period (20–50 Adam, P. (1987). ‘New South Wales Rain- years) of disappearing from the wild through continued depletion, or which occurs forests. The Nomination for the World on land whose future use is likely to change and threaten its survival. Heritage List’. (National Parks and R Rare: taxon which is rare in Australia (and hence usually in the world) but which Wildlife Service, Sydney). currently does not have any identifiable threat. Such species may be represented by a Adams, L.G. (1995). Chionogentias relatively large population in a very restricted area or by smaller populations spread (Gentianaceae), a new generic name for over a wide range or some intermediate combination of distribution pattern. the Australasian ‘snow-gentians’, and a K Poorly Known: taxon that is suspected, but not definitely known, to belong to one of revision of the Australian species. Aus- the above categories. At present accurate field distribution information is inadequate. tralian Systematic Botany 8, 935-1011. C Reserved: indicates taxon has at least one population within a national park, other Barker, W.R. (1992). Euphrasia. In ‘Flora of proclaimed conservation reserve or in an area otherwise dedicated for the protection New South Wales’, Volume 3, ed. G.J. of flora. The taxon may or may not be considered to be adequately conserved within Harden, p. 583. (New South Wales Uni- the reserve(s), as reflected by the conservation status assigned to it. Where applicable, versity Press, Kensington). the ‘C’ symbol immediately follows the conservation status symbol in the written Binns, D. (1995). ‘Flora survey Gloucester code, e.g. 2RC. and Chichester management areas en- Size-class of all reserved populations ( can be a, I, or t) vironmental impact statement support- a 1000 plants or more are known to occur within a conservation reserve(s), ing document No. 4.’ (Research Divi- I less than 1000 plants are known to occur within a conservation reserve(s); sion, State Forests of New South Wales, - reserve population size not accurately known; Sydney). t total known population reserved. Bishop, A. (1996). ‘Field Guide to the Or- chids of New South Wales and Victo- ria.’ (University of New South Wales of native grazing animals (kangaroos, many of the rare and threatened plants Press, Kensington). wombats etc.). but they are quite distinctive areas which Briggs, B.G. (1992). Plantago. In ‘Flora of Although rare plants are persisting un- warrant special management attention. New South Wales’, Volume 3, ed. G.J. der current park usage, continuation of Harden, p. 592 (New South Wales Uni- the present level of visitor use or any in- Postscript versity Press, Kensington). creased usage of the camping areas and A number of plant species considered to Briggs, J.D. and Leigh, J.H. (1996). ‘Rare or tracks may adversely impact upon the be endemic to the Barrington Top plateau threatened Australian plants’. (CSIRO plants. The most serious threat here is the are now known to occur in Ben Halls Gap Publishing: Melbourne). impact of broom spread along tracks. National Park. Due to lack of access this CMPS&F Environmental (1995). ‘Glouces- Closing key areas to vehicles and campers Park has few weed problems and does not ter and Chichester management areas until broom is better controlled and native have a broom problem. However, broom environmental impact statement. Sup- vegetation rehabilitated should be consid- would be a major problem in this Park if it porting document No. 2 hydrology and ered. established as the altitude, soil and the cli- water quality.’ (Forestry Commission Fires on the Tops could adversely affect mate are similar to the Barrington Tops of New South Wales, Pennant Hills). some rare plant populations, however, plateau. Corybas sp. A and Chiloglottis Fraser, L. and Vickery, J. (1938a). The ecol- aging populations of Acacia barringtonensis platyptera are present in Ben Halls Gap ogy of the upper Williams River and may benefit from a fire through germina- National Park, as are Tasmannia glaucifolia Barrington Tops districts. II The rain- tion of soil-stored seed. Broom is a threat and Tasmannia purpurascens. Additional forest formations. Proceedings of the here too as it also germinates in huge surveys are required to determine if other Linnean Society of New South Wales 63 (3- numbers following fire (Smith 1994) and rare or threatened plants are also present. 4), 139-84. out competes native plants. Fraser, L. and Vickery, J. (1938b). The ecol- The only known populations of some of Acknowledgments ogy of the upper Williams River and the rare plants (Grevillea granulifera and People who were consulted and assisted Barrington Tops districts. III The euca- Pterostylis sp. D) and the largest known with information on particular rare plants lypt forests and general discussion. Pro- population of Corybas sp. A on Barrington or groups of rare plants included: David ceedings of the Linnean Society of New Tops are not conserved. Jones, Centre for Plant Biodiversity South Wales 64, 1-33. The rare and threatened plant survey Research, Canberra; John Reilly, Austral- Harden, G.J. (1990–1993). ‘Flora of New of Barrington Tops and Gloucester ian Native Orchid Society, Sydney; South Wales.’ Volumes 1–4. (University Tops identified the subalpine wetlands, Peter Metcalfe, University of New Eng- of New South Wales Press, Kensing- the streams and their surrounding land, Armidale; Lyn Meredith, ROTAP ton). catchments to be of extremely high conser- Database Manager, Centre for Plant Jones, D.L. (1993). Pterostylis. In ‘Flora of vation value. Not only are they habitat for Biodiversity Research, Canberra; Chris New South Wales’, Volume. 4, ed. G.J. 176 Plant Protection Quarterly Vol.15(4) 2000 Harden, p. 171. (University of New Olde, P.M. and Marriott, N.R. (1994). A Tweedie, A.D. (1963). Part III. Climate of South Wales Press, Kensington). taxonomic revision of Grevillea arenaria the Hunter Valley. In ‘General report Jones, D.L. (1997). Six new species of and Grevillea obtusiflora (Proteaceae: on the lands of the Hunter Valley. Land Pterostylis R.Br. (Orchidaceae) from Grevilleoideae). Telopea 5, 711-33. Research Series No. 8.’ (Common- Australia. The Orchadian 12, 247-54. Smith, J.M.B. (1994). The changing eco- wealth Scientific and Industrial Re- Mort, S.J. (1983). ‘The Barrington Tops logical impact of broom (Cytisus scopar- search Organization, Melbourne). swamps – flora, ecology and conserva- ius) at Barrington Tops, New South Veness and Associates (1995). ‘Gloucester tion.’ (Unpublished document, School Wales. Plant Protection Quarterly 9, 6-11. and Chichester management areas en- of Geography, University of New Thompson, J. and Logan, V. (1991). vironmental impact statement. Sup- South Wales). Leptospermum. In ‘Flora of New South porting Document No. 1 Soils Report National Parks and Wildlife Service Wales’, Volume 2, ed. G.J. Harden, p. G. and C. Forest management areas EIS (1995). ‘North East Forest Biodiversity 154. (New South Wales University Study’. (State Forests of New South Study.’ (National Parks and Wildlife Press, Kensington). Wales, Central Region). Service).

brooms developed from this genus exist as varieties of wild-type species as well as Brooms as part of the Australian nursery industry hybrids developed from two or even three species. Often the exact origins of some of Ian AtkinsonA and Andy SheppardB the commercial broom varieties, have A Industry Development Manager, Nursery Industry Association of Australia, themselves a degree of uncertainty. Table PO Box 55, Lyons, Australian Capital Territory 2606, Australia. 1 shows a list of commercial varieties of B CRC for Weed Management Systems, CSIRO Entomology, GPO Box 1700, broom available from one supplier of plant labels to the nursery industry Canberra, Australian Capital Territory 2601, Australia. (Norwoods Industries) together with flower colour and currently accepted bo- tanical origins. Included in this list are va- Summary rieties derived directly from recognized Nursery plants that come under the reigned with respect to this for horticul- species (e.g. Cytisus ‘Cornish cream’), heading of ‘brooms’ are estimated to be tural varieties of broom, whose origins re- from horticultural varieties of recognized currently worth about $1.5 million to the main hard to trace. species (e.g. Cytisus ‘Andreanus’), and industry. Their taxonomic origins are of- There has been much switching of taxo- from hybrids between two species (e.g. ten complex and uncertain, however, nomic names of the parents of horticul- Cytisus praecox ‘Warminster broom’) Cytisus scoparius, is the most common tural broom varieties in the botanical lit- (Rowell 1991, D. Cooke personal commu- parent species and this and some other erature, which has led to plenty of confu- nication). naturalized species are banned from sale sion in the appropriateness of names used The two commonest Cytisus species by selected states. While the continued in the market place. For example the par- that have been used to generate horticul- sales of some broom varieties closely re- ent of the broom variety called ‘weeping tural varieties (C. scoparius and C. multi- lated to weedy species may pose a threat bridal veil’, Retama monosperma (L.) florus) are both naturalized in Australia to the environment through the opportu- Heywood, has in the past been included and the most frequently used parental nity of bringing in greater genetic diver- in both Cytisus and Genista, and many pa- species is C. scoparius (Table 1). Having sity, so the activities of biological control rental species have been swapped be- stated this, however, there is not necessar- programs against brooms pose a threat to tween Cytisus and Genista. ily a clear relationship between the horticultural brooms, and may lead to The aim of this contribution is to: amount of parental make up that is from a greater use of chemicals by gardeners. It (1) discuss the taxonomic origins of the known weed and the likelihood that the will be important that decisions taken to different types of broom available in developed variety will pose a threat to the manage weedy brooms, that may have an nurseries, environment if planted. There is also no impact on the nursery industry, are done (2) to summarize the economic importance direct evidence that any of the currently so in direct consultation with the indus- of brooms to the nursery industry in marketed varieties as listed in Table 1 are try. This paper discusses these issues. Australia, and of identical genetic make up to the natu- (3) discuss potential impacts of efforts to ralized brooms in Australia. For example, Introduction manage broom (Cytisus scoparius (L.) some varieties have reduced growth rates ‘Brooms’ for the nursery industry encom- Link) on the industry. or poor seed set, although if such varieties passes a whole suite of species, hybrids are compatible with naturalized weeds and varieties associated with the genera Taxonomic origins of horticultural this will provide a potential source of in- Argyrocytisus, Chamaecytisus, Cytisus, brooms creased genetic diversity and hence Genista, Retama, Spartium and Teline (Spen- The most important genus for brooms in weediness should crossovers occur (Smith cer 1997). These genera also contain spe- the nursery industry is Cytisus. Species 2000). There is plenty of anecdotal evi- cies that, worldwide, have either agricul- from this genus have contributed most to dence from gardens to suggest that most tural value or are recognized and noxious the broom horticultural varieties available varieties fail to naturalize or self-seed weeds (Holm et al. 1979, Parsons and in the market place. The main Cytisus spe- following planting, however clearly one Cuthbertson 1992, Hosking et al. 1998). As cies that have been parents of horticultural or more ‘Andreanus’ like varieties of such, some of these weed species have re- varieties in Australia are C. scoparius, Cytisus scoparius have naturalized given strictions on their sale and distribution in Cytisus multiflorus (L’Hér.) Sweet, Cytisus the frequency of its ‘egg and bacon’ flower Australia (see http:/www.weeds.org.au) purgans (L.) Boiss., Cytisus ardoini E.Fourn. colour in weedy populations in several ar- and similar legislation covers weedy in this order of frequency (D. Cooke eas. brooms in New Zealand. Confusion has personal communication). Horticultural Plant Protection Quarterly Vol.15(4) 2000 177 The value of ‘brooms’ to the sales of species already banned from sale grown by a production nursery and sec- Australian nursery industry within Australia and varieties considered ondly impacts on plants growing in gar- From the 1996/97 Australian Bureau of to pose a risk to broom weed management den and landscape situations. Statistics (ABS) report commissioned by in Australia. The question remains to what Firstly brooms in production nurseries the Nursery Industry Association of Aus- extent does the continued sale of broom will be subject to some level of pest and tralia (NIAA) and the Horticultural Re- varieties pose a threat to the Australian disease management and the biological search and Development Corporation environment? control agents may well succumb to exist- (Atkinson 1998), there are over 3000 pro- Some states in the US have considered ing control measures. However the nature duction nurseries with sales amounting to that certain nursery varieties still do pose of some agents would limit options for slightly over $539 million, at farm gate, in a significant risk and have brought in leg- control even in nurseries e.g. boring in- Australia. Approximately 55% of total islation preventing the sale of such sects are always very difficult to control. sales are made to 3500 retail garden cen- brooms (Isaacson 2000). However if such Secondly plants in gardens and landscape tres. Consequently the industry is a stance was to be considered in Australia, situations are mostly expected to flourish strongly driven by the desires of it’s main then it would be extremely important to without active pest and disease manage- customers, the Australian gardening pub- tackle this issue directly with the nursery ment. The consequences of such problems lic. However most gardeners are after a industry through consultation. We should over time are likely to include an undesir- particular ‘look’ rather than specific spe- also consider the distribution of plants by able increase in chemical use by gardeners cies so, with appropriate education, gardeners and amateurs as these may not and a decline in demand for brooms if changes can be made to the lines sold by actually be ‘sold’. they are seen as difficult to grow. nurseries. Industry would have good grounds for There are no direct figures available arguing against a blanket ban on all Conclusions from the ABS survey for broom sales. ‘brooms’ given the taxonomic diversity The sale of brooms by the Australian nurs- They would mostly be included in the ‘ex- included under that title. There would ery industry is a significant trade ($1.5 otic trees and shrubs sold in pots sizes 76 also be justifiable concerns regarding sale million annually) that could be adversely mm to 300 mm’ category which makes up of existing stock and the capital bound up impacted by controls on sale of brooms 17.4% of total greenlife sales. However, in that, prior to any ban coming into ef- and introduction of biological control working from the number of plant labels fect. Appropriate ‘lead in periods’ should agents. Research on potential biological sold by Norwood Industries (confidential be negotiated as well as significant efforts control agents must include an assessment communication) and estimates of the av- made to educate the buying public, horti- of their impact upon brooms sold by the erage sale price per pot, the authors esti- cultural media and industry about the nursery industry. Any move towards ban- mate broom sales in Australia at approxi- need for bans. ning the sale or movement of selected mately $1.5 million annually. The introduction of biological control brooms would require significant re- agents for control of broom may also im- sources for informing the media, and edu- Potential impacts on industry of pact negatively on industry. Information cating the industry and the buying public. efforts to control broom and research on the host specificity of po- However, with appropriate consultation The degree of diversity in the types of tential agents must include those brooms and education, industry can move to- broom available through the nursery in- produced by industry. Actual impact of wards sale of alternative non-weedy spe- dustry has an additional consequence. It biological control agents, which do attack cies to the gardening public. is both hard to educate people about the plants in the trade, will have two dimen- differences in varieties and hard to police sions. Firstly impacts upon stock being

Table 1. ‘Brooms’ supplied by Norwoods (from their collection of available plant tags) together with flower colour and currently accepted parental origins (Rowell 1991, D. Cooke personal communication). Horticulturally Variety name Flower colour Probable parental origins used latin namesA (Rowell 1991, D. Cooke personal communication) Cytisus ‘Burgundy’ Red with white Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Burkwoodii’ Red and white Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘C.E. Pearson’ White and red Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Chocolate soldier’ Brown and white Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Cornish cream’ White and yellow Cytisus scoparius Cytisus ‘Crimson king’ Pink and White Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Dorothy Walpole’ Red and white Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Lilac time’ Purple and white Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Peter Pan’ Pink and white Cytisus scoparius var. andreanus × Cytisus multiflorusB Cytisus ‘Snow queen’ White Cytisus multiflorus Cytisus ‘Andreanus’ Yellow and red Cytisus scoparius var. andreanus Cytisus praecox ‘Warminster broom’ White and yellow Cytisus multiflorus × Cytisus purgans Cytisus racemosus ‘Yellow broom’ Yellow Genista canariensis × Genista stenopetala (Genista fragrans) Cytisus racemosus nana ‘Dwarf genista’ Yellow Genista canariensis × Genista stenopetala Genista lydia Pale yellow Genista lydia Boiss Cytisus/Genista ‘Weeping bridal veil’ White Retama monosperma (L.) Heywood (Genista monosperma) A As they appeared on the labels thus names in brackets may be synonyms used in the industry. B The F1 hybrid from which most of these varieties were developed is called Cytisus × dallimorei developed at Kew in 1900, most varieties are selections of F2 or later, or possibly some back crosses (D. Cooke personal communication). 178 Plant Protection Quarterly Vol.15(4) 2000 Acknowledgments Holm, L., Pancho, J.V., Herberger, J.P. and Parsons, W.T. and Cuthbertson, E.G. David Cooke has put together an invalu- Plucknett, D.L. (1979). ‘A geographical (1992). ‘Noxious weeds of Australia’. able, unpublished list of horticultural va- atlas of world weeds’. (Wiley, New (Inkata Press, Melbourne and Sydney). rieties, names of brooms in Australia and York). Rowell, R.J. (1991). ‘Ornamental flowering their most likely parentage. Table 1 would Hosking, J.R., Smith, J.M.B. and Sheppard, shrubs in Australia’. (New South Wales not have been possible without this (Full A.W. (1998). Cytisus scoparius (L.) Link University Press, Kensington). list available from him at Animal and ssp. scoparius. In ‘The biology of Aus- Smith, J.M.B. (2000). An introduction to Plant Control Commission, GPO Box tralian weeds’, Volume 2, eds F.D. the biogeography and ecology of 1671, Adelaide, South Australia 5001). Panetta, R.H. Groves and R.C.H. Shep- broom (Cytisus scoparius) in Australia. Sharon Corey, John Hosking and Kate herd, pp. 77-88. (R.G. and F.J. Proceedings of the broom symposium Blood for critically reviewing the manu- Richardson, Melbourne). held at Ellerston and Moonan, 16–17 script. Isaacson, D. (2000) Impacts of broom November 1998, eds A.W. Sheppard (Cytisus scoparius), in western North and J.R. Hosking. Plant Protection Quar- References America. Proceedings of the broom terly 15, 140-4. Atkinson, I. (ed.) (1998). Lies damned lies symposium held at Ellerston and Spencer, R. (1997). A clean sweep for new and statistics! The Nursery Papers, is- Moonan, 16–17 November 1998, eds brooms. Australian Horticulture Dec. sue 1998/016, 1-2. A.W. Sheppard and J.R. Hosking. Plant 1997, p. 18. Protection Quarterly 15, 145-8.

(Hosking et al. 1998, Peterson and Prasad 1999, Smith 2000), often forming a dense Broom (Cytisus scoparius (L.) Link) and fire: monoculture to 5 m in height and quickly management implications establishing large long-lived seedbanks (up to 60 000 seeds m-2, P. Downey unpub- lished data). Broom responds well to dis- Paul O. Downey, CRC for Weed Management Systems, CSIRO Entomology, turbance and if subject to favourable con- GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia. ditions can grow 1.5 m in less than one year (P. Downey unpublished data), reaching reproductive capacity in a mini- mum of three years (Hosking et al. 1998, Summary Introduction Downey and Smith 2000). Fire is often employed to control Over 220 plant species were declared as At present herbicides are the main con- populations of weeds especially over noxious weeds in Australia in 1992 (Par- trol option for broom in its exotic range. large and/or remote areas. However, how sons and Cuthbertson 1992), and approxi- Herbicides are expensive, logistically dif- fire may favour subsequent re-invasion, mately ten times this number have become ficult and costly to apply in remote loca- either from the original or other weeds is naturalized since the arrival of European tions (Carter and Signor 2000, Schroder poorly understood. There is a need to settlers, some 210 years ago (Humphries and Howard 2000). The biological control know how weed species respond to fire et al. 1991). They occur in almost every program in Australia is still in its infancy, and to incorporate this knowledge into landscape and can modify the pre-inva- but based on overseas experience could management strategies for both fire and sion disturbance regimes to their advan- prove increasingly beneficial over time weeds. This paper explores how broom tage and the demise of native species (Syrett et al. 1999). Due to broom vigour (Cytisus scoparius) responds to fire. Fire (Mack and D’Antonio 1998). A dominant and longevity of its seeds, any control can cause high seed mortality in broom and frequent disturbance in the Austral- strategy must be long-term. Fire can de- seedbanks reducing them to less than ian landscape is fire. With a long history plete the seedbank to 8% of pre-fire levels 10% of pre-fire levels, depending on the of Aboriginal burning (Nicholson 1981) either by killing or stimulating germina- timing and intensity of the fire. It is the many native plant species have developed tion of seeds (Bossard 1990). Following only potential management tool avail- strategies to survive periodic fires. Many fire there is a three-year window of oppor- able that can directly target the weed-invaded environments are subject tunity to intensely manage broom seed- seedbank, however, remaining viable to fires, be it a wildfire or a controlled banks and subsequent recruitment, before seeds in the soil are sufficient for stand burn. Fire is still frequently used in weed freshly produced seed will re-enter the replacement. Any effects of fire on management even though very little is system. In light of this the potential ben- seedbank germination and subsequent known about its effectiveness and how efits of fire are very attractive to land- seedling survival in the field had negli- weed species respond to fire (Downey holders. gible consequences on recruitment 12 1999). This practice may have arisen from Rigorous and comparable experimental months after the fire. However, seed- the transfer of agriculture-based weed data on how fire affects broom seedbank bank decline in burned soil samples pot- management to native ecosystems and the size and its dormancy profile from a range ted out in the glasshouse showed a logistic constraints of broad-scale weed of sites are hard to obtain as fire intensity marked difference compared to un- management in remote areas (Humphries varies, particularly between experimental burned over the same period. Burned et al. 1991). and wild fires. Data presented here are broom plants die, but lightly scorched Broom (Cytisus scoparius (L.) Link from three sites. Two of the sites had plants have the capacity to resprout. Us- subsp. scoparius) is an exotic, leguminous fires deliberately lit to manage broom. ing fire to control broom should be and deciduous shrub, which invades agri- These fires were relatively low in intensity avoided, unless intensive follow-up cultural and natural ecosystems in tem- and in one case no pre-fire data were treatments are planned as part of an inte- perate areas of high annual rainfall. It is a available. Data from a third site were grated weed management strategy. major weed in many parts of the world collected opportunistically following a Plant Protection Quarterly Vol.15(4) 2000 179 spatially variable, but in some spots, quite The plot at Barrington Tops was sam- Analysis intense wildfire, which in places probably pled twice prior to the burn in October These data were used to obtain mean approached the maximum fire intensity (four months pre-burn) and December number of broom seeds and seedlings m-2 possible given fuels derived solely from 1997 (two months pre-burn), using 25 and at each site by back-transforming means broom. 30, 3.2 cm diameter soil cores respectively. of ln (x+1) transformed data of seeds per The aim of this paper is to present data Cores taken in December were lumped core and seedlings per quadrat. Mean on how broom responds to fire, as meas- into groups of three prior to processing, number of seeds m-2 was considered to be ured through changes in the soil due to the high frequency of seedless cores the ‘actual’ seedbank (some seeds in the seedbank, germination and mortality of in the October samples. Following the fire, soil cores were in the process of germinat- seedlings. These findings are subse- samples were taken after 12 months (in ing and were thus considered part of the quently discussed in a management con- February 1999). In addition, five soil sam- actual seedbank) on the given sampling text for this species. ples of 20 × 20 cm in area and to a depth of date, while mean number of seeds m-2 plus 10 cm were randomly collected and com- mean number of new seedlings m-2 was Methods bined (to form one sample), from both the considered to be the ‘original’ seedbank. Study sites yet-to-be burned and unburned areas, at Three sites were selected in widely sepa- the Barrington Tops site, in January 1998. Fire intensity – Majors Creek rated locations in south-eastern Australia, Similar samples were taken from the In three, 1 m2 randomly placed quadrats on the basis of their known fire history. burned site three months after the burn in in each of the three burned areas at Majors Two sites were in New South Wales at June 1998. These samples were put out in Creek, the heights and minimum stem di- Majors Creek (35° 30'S, 149° 43'E) and trays in the glasshouse and weekly broom ameters at the base and at the top of all Barrington Tops (31° 57'S, 151° 28'E), germination rates were established for burned stumps were recorded. Basal di- while the third site, ‘The Lanes’, was on both burned and unburned samples to es- ameters only were recorded from the con- the Bogong High Plains in the Victorian tablish seedbank decay rates under con- trol area (i.e. of live plants). All measure- Alps National Park (36° 55'S, 147° 25'E). trolled conditions. After 13 months (i.e. 12 ments were taken at the first sampling Each site had a mature broom infestation months post fire) and nine months soil date only and then used to define relative prior to burning. Majors Creek had been from each tray was washed through a 0.5 fire intensity between the three burned ar- burned in March 1998 by a wildfire over mm mesh sieve and remaining broom eas. The area with the lowest average approximately 15 ha leaving about 65% of seeds counted. stump height and the largest minimum the broom infestation intact. A 25 × 25 m At ‘The Lanes’ samples were collected mean stem diameter at the top was con- plot at Barrington Tops had been slashed in January 1999 in two areas correspond- sidered to have experienced the highest with chainsaws in October 1997 and the ing to 21 and 58 months after the fire. fire intensity and the area with the tallest slash spread evenly across the site and left Thirty, 7.3 cm diameter soil cores were mean stump heights and the smallest to dry. This plot became part of a control taken at random throughout each area. No mean stem diameter at the top was con- burn in February 1998. After this the control site could be established here as all sidered to have experienced the lowest height reached by scorching on the sur- mature broom stands had been removed fire intensity. These data were also used rounding vegetation was recorded. At by Parks Victoria staff. to estimate number and sizes of broom ‘The Lanes’, two areas had been burned Soil from each core was washed plants that had died as a result of the under experimental conditions; one in through a 0.5 mm mesh sieve and all fire. March 1994 (approximately 1 ha, see broom seeds extracted from the remains. Robertson et al. 1999) and the other in All un-germinated seeds present in the Results April 1997 (several ha). The second burn post-fire soil cores were tested for Fire intensity assessments at Majors was an attempt to control broom by Parks germinability in a growth cabinet, regu- Creek Victoria. lated at 15–25°C (min-max) with 10 hours Observed values of stem height and apical of light per 24 hours. Each seed was scari- and basal stem diameters of burned Seedbank sampling fied with a scalpel (by placing a small nick stumps left after the fire in the three Sampling consisted of 10 cm deep soil in the seedcoat) and then placed into a burned areas at Majors Creek are given in cores. Below this depth few broom seeds Petri dish with damp filter paper and wa- Figure 1. The area with the tallest stumps are found (A. Sheppard personal commu- tered daily. Daily germination rates were also had the smallest apical stem diam- nication). taken over a period of 12-13 days, at which eters and vice versa. The area with the tall- Following the wildfire at Majors Creek, stage all remaining seeds were tested for est stumps was also the only burned area four sampling areas were selected (each viability with Tetrazolium® according to where any broom resprouting post-fire approximately 0.5 ha in area). One was methods set out by Grabe (1970). Seeds was observed (see below). This allowed not burnt while the others appeared to from the controls were not tested for relative fire intensity to be allocated to have experienced different fire intensities. germinability or viability as previous tests each burned area at this site and used sub- The unburned area was in mature broom had shown that 98% of broom seeds are sequently for presentation of seedbank within 30 m of where the fire had passed, viable (Hosking et al. 1998), a similar level and seedling density data in Tables 1–3. while the other burned areas were allo- being found in California (Bossard 1990). cated the relative fire intensities of low, Seedbank depletion medium and high, based on the height Assessing germination and At the Majors Creek site broom seedbanks and minimum diameter of burned broom establishment were 3.3–11% of the level in unburned ar- stumps remaining (see below). Samples At each site, on each of the same sampling eas six months after the wildfire (Table 1). consisted of 25, 3.1 cm diameter soil cores dates, number and approximate age of Assessed fire intensity had relatively little positioned at random within each sample seedlings in 12 random quadrats of 25 × effect on magnitude of seed loss to fire, as area. Areas were sampled in September 25 cm was recorded using the following the smallest estimated decline in seedbank 1998, six months after the fire. The categories: this season’s seedling (TS – density after the fire (89%) was found in unburned and high intensity burn areas non-woody plants with cotyledons), this the area where the fire intensity was as- were re-sampled at 12 months in March year’s older seedling (TY – woody, sessed as being highest. In this area the 1999. The other areas could not be relo- unbranched plants) and last year’s seed- seedbank was again estimated 6 months cated for sampling at that time. ling (LY – woody, branched plants). later (i.e. 12 months after the fire) and 180 Plant Protection Quarterly Vol.15(4) 2000 found to have declined to 98% (688 seeds Seedbank and seedling density density was higher in burned plots 210 m-2) of the background seedbank. Six months after the fire at Majors Creek, seedlings m-2) than in unburned plots (79 The control burn at Barrington Tops seedling density in burned areas demon- seedlings m-2, Table 2), but lack of data was of very low intensity with a scorch strated seedbank depletion to levels an or- prevented assessment of whether this re- height of 2–3 m. Seedbanks at the site a der of magnitude lower than in the flected the available seedbank and 12 year after the fire were approximately 57% unburned area (Tables 1 and 2). Fire did months after the fire there was no differ- of the density two months before the fire not appear to affect the chance of a seed in ence in seedling density between burned (Table 1). At ‘The Lanes’, where lack of an the seedbank becoming an established and unburned plots (Table 2). Broom seed adequate control site prevented assess- seedling as 18–47% of the ‘original’ seed- germination rates from Barrington Tops, ment of seedbank depletion in response to bank had established as seedlings in the based on soil collected two months pre- fire, viable seeds were still present in the burned area, while 19% of the ‘original’ burn and placed in glasshouse trays, seedbank at about 1500 seeds m-2, 58 seedbank had established as seedlings in showed a 28.7% reduction in the seedbank months after the fire when regenerated unburned plots (Table 1). At Barrington at the 12 month post-fire stage (Table 3). plants were starting to shed seeds (Table Tops six months after the fire, seedling Soil collected from within the burned area 1). showed a 52.3% reduction in the seed- bank, over the last nine months of a 12 month post-fire period. The difference ob- served in germination rates between 35 14 burned and unburned sites was highest in mean diameter at top the 3–6 month period, but still present 12 mean diameter at base 30 mean height 12 months after fire (Table 3). Germinability and viability of broom 25 10 seeds Broom seeds which remained in the soil 20 8 following fire exhibited a high level of germinability which appeared to decline 15 6 with time as highlighted by only 3% of seeds being germinable after 58 months. Height (cm) 10 4 Diameter (cm) Despite this viability of ungerminated seedbank seeds was 94–100% even after 58 months. 5 2 Seedling survival 0 0 At Majors Creek seedlings appeared to low medium high control survive longer in burned (assessed high intensity) than in unburned areas as re- Fire intensity flected by densities of TS seedlings found six months after the fire and numbers of Figure 1. The mean height of burned broom plants and their base diameters TY and LY seedlings found 12 months and top diameters. after the fire (Table 2). Actual seedling

Table 1. Broom seedbank and seedling density at different times following fires of differing intensity, at three sites in eastern Australia. Site Burn condition Time since Viable seeds m-2 % seedbank Total seedlings m-2 Seedlings fire (months) in seedbankA reduction with (back-transformed as a % of (mean ln (x+1) respect to from mean ln (x+1) ‘original’ transformed seeds unburned area transformed seedbankB per core ± SE quadrat-1 ± SE seedlings given in brackets) given in brackets) Majors Unburned 6 28 377 (22.86 ± 0.2) 6 620 (34.48 ± 0.2) 19 Creek 12 18 814 (15.15 ± 0.2) 61 (0.32 ± 0.1) 0.4 Low intensityD 6 1 862 (1.50 ± 0.2) 93 699 (3.64 ± 0.2) 27 Medium intensityD 6 699 (0.56 ± 0.1) 97 626 (3.27 ± 0.2) 47 High intensityD 6 3 117 (2.50 ± 0.2) 89 692 (3.60 ± 0.3) 18 12 688 (0.55 ± 0.1) 98 484 (2.52 ± 0.3) 13 Barrington Pre-fire -4 1 756 (1.33 ± 0.2) Tops Pre-fire -2 1 117 (2.53 ± 0.4) Very low intensity 12 482 (2.02 ± 0.2) 57C 103 (0.8 ± 0.2) 18 ‘The Control burn 21 2 482 (10.40 ± 0.1) No data 1 486 (7.7 ± 0.2) 37 Lanes’ Low intensityE 58 1 470 (6.16 ± 0.2) No data 261 (1.4 ± 0.3) 15 A Calculated from back-transformed values of seeds per core, where core size varied across sites (see text for details). B Original seedbank = seedlings + viable seeds at the time samples were taken. C % of sample taken 2 months before the fire. D Intensity estimated (see text for details). E See Robertson et al. 1999. Plant Protection Quarterly Vol.15(4) 2000 181 densities were eight times higher in this Discussion seeds are killed outright, while tempera- burned area than in the unburned area 12 Fire intensity and seedbank depletion tures around 65°C stimulate germination. months after the fire despite being an or- The degree to which broom seedbanks Fire intensity can also prolong the period der of magnitude less at six months after were depleted by fire in this study were of heat exposure, thereby killing more the fire (Table 2). This pattern was not re- comparable with the 92% reduction ob- seeds (Bossard 1990). Clearly, the drier the flected at Barrington Tops where the served by Bossard (1990) in California. soil at burning the greater the level of burned plot had a higher TS seedling den- The effect of fire intensity on seedbank seedbank depletion achieved. In their sity at six months but a lower TY+LY seed- depletion could not be detected at Majors study at ‘The Lanes’ Robertson et al. (1999) ling density at 12 months. This suggests Creek, the only site where an attempt was found that as it rained the day prior to seedling survival may be more related to made to select areas experiencing differ- burning, the soil temperatures during the initial seedling density than the effect of ing fire intensity. However the much fire were low. Hardman (1980) found the fire per se. It should also be noted that lower (54%) reduction in the seedbank 12 similar limitations during ten years of us- seedlings at the unburned site at Majors months after the low intensity fire at ing fire to control broom on Barrington Creek, but not at Barrington Tops, were Barrington Tops suggests fire intensity Tops. While he concluded that burning of under an undisturbed mature broom may influence the degree of seedbank de- broom should be carried out in drier hot- canopy. pletion to some degree. ter months, the availability of suitable cli- Variation in seedbank depletion fol- matic conditions for broom control burns Mature broom mortality lowing fires will be influenced by interac- is a limiting factor in its applicability as a At Majors Creek most plants that were se- tions between fire intensity and soil mois- management tool. The greatest seedbank verely burned died irrespective of age. ture and how this affects heat penetration depletion estimated in this study was at Scorched or partially burned plants (e.g. into the soil. Soil temperatures during a Majors Creek, where broom was burned those on the edge of a fire) could re-sprout. fire cannot exceed 100°C until soil mois- by a wildfire during a period when condi- Re-sprouting (3% of stumps) at six months ture has been boiled away. However, a fire tions were such that there was a total fire post-fire was only observed in the area as- over dry soils can lead to temperatures of ban in the shire. This fire therefore oc- sessed as having experienced a low inten- several hundred °C in the top few centi- curred when soil moisture was low and sity fire. This was similar to ‘The Lanes’ metres (M. Gill personal communication), thus soil heat penetration was maximal, site, but due to the interval between the which is where the majority of broom leading to similar levels of seedbank de- fire and sampling date, it could not be con- seeds are present (P. Downey unpub- pletion across all three fire ‘intensities’. clusively stated that fire alone led to plant lished data). Bossard (1990) found that Factors other than observed fire intensity death there. once temperatures reach 150°C broom (when assessed in terms of combustion of above ground biomass), such as site loca- tion and soil moisture levels and the size Table 2. Broom seedling density in the field at different times following of the broom seedbank relative to that of native species may therefore be more im- fires of differing intensity, at three sites in eastern Australia divided into portant for understanding fire impact on three seedling age classes. the seedbank and subsequent stand regen- Site Burn condition Time since Density of Density of Density of eration. fire TS seedlings TY seedlings LY seedlings Bradstock and Auld (1995) found that (months) m-2 A m-2 A m-2 A post-fire soil temperatures were similar to or higher than those recorded during a Majors Unburned 6 6613 6 3 fire, for longer periods of time, suggesting Creek 12 0 32 0 that post-fire dynamics may be important Low intensityB 6 699 0 0 for germination of leguminous shrubs. Medium intensityB 6 626 0 0 Despite this and not collecting samples till High intensityB 6 692 0 0 either three or six months post-fire, there 12 9 384 92 seems to be little difference at the 12 months stage in terms of recruitment, Barrington Unburned 6 70 6 3 which may be due to high levels of seed- Tops 12 43 47 10 ling mortality (Downey and Smith 2000). Low intensity 6 210 0 0 As in this study, others who sampled 12 83 21 0 seedbanks following a fire, found that there was still enough viable seed left in ‘The Control burn 21 1486 0 0 the soil to allow stand replacement Lanes’ Low intensityB 58 155 6 10 (Robertson et al. 1999). Studies on similar A from back-transformed data; TS – this season’s, TY – this year’s, LY – last year’s (see weeds such as Spartium junceum L. text above). (Fernandez-Santos et al. in press) and B see notes on table 1 for details. Genista monspessulana (L.) L.A.S.Johnson

Table 3. Germination of broom based on weekly counts taken from soil collected at Barrington Tops and put out in trays in the glasshouse. Soil collected from burned area three months post-fire. Period: 3–6 months post-fire 6–12 months post-fire 0–12 months post-fire Burned condition total number % of actual total number % of actual total germination of seedlings seedbank in tray of seedlings seedbank in tray number and % germinated that germinated germinated that germinated in brackets Unburned 28 (76A) 7.3 (19A) 34 8.9 110 (28.7) Very low intensity 48 36.4 21 15.9 69 (52.3) A value for the full 0–6 months, burned samples weren’t collected until three months after the fire. 182 Plant Protection Quarterly Vol.15(4) 2000 (J. Lloyd personal communication) have depend on density, standing biomass/ plan and carry out long-term post-fire also shown that fire does not completely fuel loads (combination of broom and the management will quickly nullify benefits destroy viable seed. other vegetation present) and to a lesser of fire and may indeed increase broom degree climatic conditions preceding and dominance due to the favourable seedbed Germination rates during the fire. The general effect broom created. It will be important therefore not Results from trays indicated that germina- has on fire regimes remains unanswered, to apply fire as a management tool to tion can occur throughout the year with- but potential effects on the native commu- broom areas too large to effectively man- out any major flushes when there is no nity may be more devastating than weed age thereafter, and large-scale fires are seed input, suggesting that seasonal invasion alone (Mack and D’Antonio probably the main reason why wildfires flushes in germination are attributable to 1998). in broom cause more harm than good to fresh seed, and that seedbank decay/de- cohabiting native species. Follow up treat- cline may be a slow process (7% in the first Fire and broom management ments may become less time consuming six months reaching 11% after 12 months). To develop a safe fire-based management as germinability of the remaining seed- However, based on glasshouse experi- strategy that both removes broom stands bank declines in the presence of compet- ments that were monitored weekly, the and usefully depletes underlying broom ing ground cover. Collection of better data rates were much higher with 16.7 and seedbanks requires greater understanding relating to this is of paramount impor- 23.7% respectively. There are two reasons of fire intensity requirements in relation to tance for designing long-term post-fire for this. Firstly the glasshouse is a more soil conditions and how this can be most weed management plans. benign environment, and secondly seed- effectively manipulated (e.g. by slashing ling mortality in the field is extremely broom prior to use of fire). Selecting ap- high (Downey and Smith 2000) and by propriate climatic conditions for the fire Acknowledgments sampling at six month intervals in the will also be important in the balance be- The author acknowledges Val O’Hare for field many seedlings will die without be- tween fire effectiveness and safety. In re- allowing the study to be undertaken on ing recorded, as demonstrated by the dis- mote areas an intense wildfire may pro- her property at Majors Creek, State For- crepancies between actual germination vide a window of opportunity for broom ests of NSW for allowing the study to be and the change in the seedbank at management, but strategies will need to conducted at Barrington Tops and for help Barrington Tops (113 seedlings m-2 re- be quickly available to benefit from this with burning, and Parks Victoria for al- corded in 12 months, but a reduction in type of event. Fire management strategies lowing the study to be conducted at ‘The the seedbank of 566 m-2). Decreased ger- need to include follow-up treatment for an Lanes’. The author is also grateful for help mination rates of seed from the longer fire extended period as broom seeds have a provided during the project by Anthony interval sites suggests that the longer seed long dormancy period. These follow-up Signor, Ron Reilly, Karina FitzGerald, Pe- remains in the soil the more difficult ger- strategies need to be incorporated into a ter Berenston, John Hosking, Andy mination becomes, despite high seed vi- integrated weed management strategy for Sheppard, Jeremy Smith and Kirsten ability. broom. Overeem. The author appreciated discus- Post-fire strategies are important in sions with Andy Sheppard, Jeremy Smith Seedling survival enabling native species to regain ground and John Morgan and additionally, com- The present study found clear evidence previously occupied by weeds as high- ments made on earlier versions of this that fire created a seedbed that led to lighted by Robertson et al. (1999). Post-fire manuscript by Andy Sheppard, John higher survival of seedlings. Seedling sur- treatments should minimize disturbance Hosking and Jeremy Smith. vival, estimated by counting number of and target regenerating broom just before new seedlings after six months, and then first flowering (three years). Disturbance number of woody and branched seedlings may enhance the chance of a seedling sur- References after 12 months suggested that absolute viving to reproduction which is generally Bradstock, R.A. and Auld, T.A. (1995). Soil initial seedling density was more related very low in Australia (less than 2%, Rees temperatures during experimental to later numbers than whether these seeds and Paynter 1997, Downey and Smith bushfires in relation to fire intensity: had appeared in a burned plot. Unfortu- 2000). Broom seedling survival can be re- consequences for legume germination nately this conclusion is only based on duced by a grass cover (P. Downey un- and fire management in south-eastern comparisons at two sites. published data) which can be encouraged Australia. Journal of Applied Ecology 32, by selective post-fire treatments. Observa- 76-84. Broom and fire tions from all three sites suggests that re- Bossard, C.C. (1990). Secrets of an ecologi- Like other exotic species (Mack and cruitment of native Poa species is slow fol- cal interloper: ecological studies on D’Antonio 1998), broom may modify eco- lowing fire, giving broom a competitive Cytisus scoparius (Scotch broom) in Cali- systems it invades to the detriment of sur- edge in these grass-dominated environ- fornia. Ph.D. Thesis, University of Cali- rounding native species. Prior to broom ments. fornia, Davis. invasion, Barrington Tops was subalpine Carter, K. and Signor, A. (2000). Control- open eucalypt woodland, with a grassy Conclusions ling broom (Cytisus scoparius (L.) Link) understorey, supporting a low density of Fire alone cannot control broom, but if in native forest ecosystems. Proceed- shrubs. As in most invaded areas, broom used as part of an integrated weed man- ings of the broom symposium held at now forms a dense shrub layer, over top- agement strategy it could be very effec- Ellerston and Moonan, 16–17 Novem- ping a depleted grass layer. A fire in this tive. As fire is the only management tool ber 1998, eds A.W. Sheppard, J.R. situation would be a higher intensity that can directly remove broom stands Hosking. Plant Protection Quarterly 15, shrub fire instead of a grass fire in which and deplete broom seedbanks, it can pro- 165-6. fire temperatures and duration would be vide a window to manage broom before Csurhes, S. and Edwards, R. (1998). Poten- lower (M. Gill personal communication). the stand regenerates. This study has tial Environmental Weeds in Australia: There is some debate as to whether living shown, however, that using fire effec- candidate species for preventative con- broom is very flammable (Csurhes and tively is not an easy task and requires an trol. National Weeds Program, Envi- Edwards 1998) or a fire retardant understanding of fire behaviour and in- ronment Australia, Canberra. (Hardman 1980). The degree to which tensity (through variables like soil mois- Downey, P.O. (1999). Fire and weeds: a broom will modify fire regimes may ture, climate and fuel loads). Failure to management tool or Pandora’s box? Plant Protection Quarterly Vol.15(4) 2000 183 Proceedings of the Bushfire 99 confer- Panetta, R.H. Groves, and R.C.H. Shep- Robertson, D.C., Morgan, J.W. and White, ence, Albury, 7–9 July 1999, pp. 111-7. herd, pp. 77-88. (R.G and F.J. M. (1999). Use of prescribed fire to (Charles Sturt University, Albury). Richardson, Melbourne). enhance control of English broom Downey, P.O. and Smith, J.M.B. (2000). Humphries, S.E., Groves, R.H. and (Cytisus scoparius) invading a subalpine Demography of the invasive shrub Mitchell, D.S. (1991). Plant invasions of snowgum woodland in Victoria. Plant Scotch broom (Cytisus scoparius (L.) Australian ecosystems: a status review Protection Quarterly 14, 51-6. Link) at Barrington Tops, NSW: and management directions. Kowari 2, Schroder, M. and Howard, C. (2000). Con- insights for management. Austral Ecol- 1-134. trolling broom (Cytisus scoparius (L.) ogy 25(5). Mack, M.C. and D’Antonio, C.M. (1998). Link) in natural ecosystems in Fernandez-Santos, B., Gomez-Gutierrez, Impacts of biological invasions on dis- Barrington Tops National Park. Pro- J.M. and Moreno-Marcos, G. (In press). turbance regimes. Tree 13, 195-8. ceedings of the broom symposium held The effect of traditional Spanish rural- Nicholson, P.H. (1981). Fire and the Aus- at Ellerston and Moonan, 16–17 No- practice perturbations on the regenera- tralian Aborigine-an enigma. In ‘Fire vember 1998, eds A.W. Sheppard, J.R. tive response in Cytisus multiflorius. and the Australian Biota’, eds A.M. Hosking. Plant Protection Quarterly 15, Grabe, D.F. (ed.) (1970). Tetrazolium Test- Gill, R.H. Groves and I.R. Noble, pp. 55- 169-72. ing Handbook for Agricultural Seeds, 76. (Australian Academy of Science, Smith, J.M.B. (2000). An introduction to The tetrazolium testing committee, The Canberra). the biogeography and ecology of Association, Amherst, Massachusetts, Parsons, W.T. and Cuthbertson, E.G. broom (Cytisus scoparius) in Australia. 62 pp. (1992). ‘Noxious Weeds of Australia’. Proceedings of the broom symposium Hardman, D.C. (1980) Scottish Broom (Inkata Press, Melbourne). held at Ellerston and Moonan, 16–17 (Sarothomnus scoparius): Control Pro- Peterson, D.J. and Prasad, R. (1999). The November 1998, eds A.W. Sheppard, gramme, Barrington Tops National biology of Canadian weeds. 109. J.R. Hosking. Plant Protection Quarterly Park. New South Wales National Cytisus scoparius (L.) Link. Canadian 15, 140-4. Parkes and Wildlife Service unpub- Journal of Plant Sciences 78, 497-504. Syrett P., Fowler S.V., Coombs E.M., lished report. Rees, M. and Paynter, Q. (1997). Biological Hosking J.R., Markin G.P., Paynter Q.E. Hosking, J.R., Smith, J.M.B. and Sheppard, control of scotch broom: modelling the and Sheppard A.W. (1999). The poten- A.W. (1998). Cytisus scoparius (L.) Link determinants of abundance and the po- tial for biological control of Scotch ssp. scoparius. In ‘The Biology of Aus- tential impact of introduced insect her- broom (Cytisus scoparius) (Fabaceae) tralian Weeds’, Volume 2, eds F.D. bivores. Journal of Applied Ecology 34, and related weedy species. Biocontrol 1203-22. News and Information 20, 17N-34N.

West Coast Weed Strategy The West Coast Weed Strategy was a five- Cutting and mulching broom (Cytisus scoparius (L.) year plan put forward by Bob Curley Link): a Tasmanian perspective (Ranger, Parks and Wildlife Service) in 1992 to coordinate weed control activities currently being undertaken by a number Eddie Talbot, West Coast Weed Strategy, PO Box 598, Queenstown, of organizations with independent goals. Tasmania 7467, Australia. This was the first community-based re- gional weed management strategy set up in Tasmania and led to the setting up of a Summary liver complaints (Launert 1981, Chevallier West Coast Landcare Group. The major This paper reviews current practices for 1996). Despite this diverse utilitarian his- weed species included were gorse (Ulex broom control used in north-west Tas- tory, none of these uses have yet been europaeus L.), brooms (C. scoparius and mania and describes the instigation and transferred to Australia where the plant Genista monspessulana L.A.S.Johnson), operating of the first community-based has become as serious noxious weed. pampass grass (Cortaderia spp.), black- regional weed management strategy de- Following introduction into Tasmania berry (Rubus frutisosus L. complex), and veloped in Australia. It also presents and soon after colonization, broom has spread Elisha’s tears (Leycesteria formosa Wall.). costs the ‘cut and mulch’ method devel- to be a significant weed of forestry, min- Landcare and various private and govern- oped for broom control as part of a ing company and public land and native ment organizations sponsored a part-time project by the West Coast Weed Strategy vegetation in north-west Tasmania, par- coordinator position from May 1994. The and funded by the National Heritage ticularly around the town of Waratah coordinator’s role is to coordinate weed Trust. where this weed has special ‘secondary control efforts in the group, provide rel- weed’ status under the State Noxious evant information, represent the group at Introduction Weeds Act 1964. It is also a scattered weed meetings, organize weed control meetings Broom (Cytisus scoparius (L.) Link), has a in other parts of Tasmania (J. Ireson per- and promote and sustain interest in the long history of cultural uses in its native sonal communication). It is now estimated Strategy. The coordinator is also responsi- range. In addition to being adopted by the to have infested at least 33 000 ha in the ble for maintaining in-kind funding from English king, Henry II (the ‘Plantagenet’ state (Hosking et al. 1998). This paper first affected organizations and councils and to from planta genista) as a personal emblem, describes the West Coast Weed Strategy; a obtain external grants (e.g. from the Na- these cultural uses also included: an agent project which developed a five-year plan tional Heritage Trust) to run this weed for tanning leather; as a source for yellow to coordinate major weed control efforts in control initiative. However, without active dye; for broom, rope and paper manufac- north-west Tasmania and then reviews involvement of supporting organizations ture; as rabbit feed; and for making an al- past broom control methods in this region and their adherence to the agreed plan the ternative medicine for use as a heart tonic, and describes a successful ‘cut and mulch’ strategy would fail. Areas of concern to diuretic, emetic, purgative and relief from control method for broom. the Strategy were to tackle weed problems 184 Plant Protection Quarterly Vol.15(4) 2000 in urban areas, monitor spread of weeds into bush via off-road tracks and control weeds in areas adjacent to the World Her- itage Areas. Since 1997 the West Coast Weed Strat- egy has obtained regular financial support from the National Heritage Trust, the West Coast Council and other stake- holders such as the Hydro Electric Com- mission and Renison Bell Gold Mines. The main successful management strategy for broom trialed by the West Coast Weed Strategy is the cut and mulch method.

Lessons to be learned from north- west Tasmania A number of different broom control pro- cedures have been used in the region. These and their effectiveness are dis- cussed below.

Bulldozing and fire Figure 1. Broom demonstration site at Waratah prior to the cut and mulch Bulldozing infestations into heaps and method being applied on 26 March 1996. burning resulting weed mounds has been a common practice. This causes massive soil disturbance and physical movement of broom plants not only burying seeds but also spreading seeds beyond the origi- nal infestation and leaving a perfect seed bed for regrowth. Topsoil is often buried in the process. In at least one situation (i.e. Waratah, Tasmania) this practice and a lack of follow up treatments exacerbated the broom problem throughout the town.

Herbicides In the past the general practice in the re- gion has been to control broom along roadsides with herbicides. This approach generally led to poor control. Plants along roadsides were sprayed to a set distance onto the verge resulting in only half of many plants being affected by herbicide. Such plants regrew and produced many seeds allowing continued spread out into adjacent paddocks or bush. These at- tempts to control broom also failed due to Figure 2. Picture of tractor and mulcher attachment used during the broom inadequate consultation with adjoining landowners. Since the instigation of the control demonstration trial. Strategy cooperation between adjacent landholders and a strategic spraying pro- gram by the Civil Construction Company Cut and mulch method using machinery The tractor and mulcher consisted of a has improved the success of chemical con- The cut and mulching method was devel- 115 horse power four wheel drive tractor trol programs. oped as a response to the tendency of pulling a Seppi Heavy Duty Forest Mower many landholders to think that herbicides which has a large rotating drum equipped Treating large infestations are the only answer to woody weed con- with what are termed ‘Hammers’, driven Large infestations have been generally trol. The Coordinator teamed up with the by the power take-off (Figure 2). As the treated haphazardly, such as by spraying commercial operations of a small com- tractor pushes and flattens plants the ma- herbicides around the perimeter, then pany (Silvi Culture Contracting, Laun- chine chews them up and deposits the when dry setting fire to the infestation. ceston) marketing vegetation mulching of leftovers as mulch. The mulcher did not There are inherent fire risks in this prac- inter-row weeds in plantations, where ac- disturb the soil surface and the tractor tice and it has failed to be used in any cess was required for pruning, thinning or caused much less disturbance than a bull- regulated manner. Risks of such methods as a means of retarding fire. The longest dozer and therefore offered little opportu- getting out of control will be high in, for running trial started on 29 March 1996 nity for sunlight to stimulate buried dor- example, semi-urban settings. The treat- and used the cut and mulch method on a mant seeds. Both a forward and reverse ments also initially leave the land unus- 0.4 ha plot of relatively flat ground that cut were necessary and the treatment able due to the many burnt stems sticking was densely covered by mature broom lasted 2–3 hours at a contracted cost of out of the ground. (3.5 m high) that had been present on the $1110 ha-1. A further contract cleared 21 ha site for many years (Figure 1). at a total cost of $17 800, which reduced Plant Protection Quarterly Vol.15(4) 2000 185 costs ha-1, and was cheaper and more ef- fective than earlier contracts to clear the land of broom using bulldozers. The thickness of the mulch depended upon biomass of broom plants per unit area. Mulch, 15–20 cm thick, significantly suppressed and retarded broom regenera- tion. No regeneration from seed was ob- served in these areas after 12 months. Variation in terrain and broom biomass, however, did lead to some variation in mulch thickness and effective broom sup- pression. In 1998, at 24 months (Figure 3), a few regenerating broom plants were found that had reached 30 cm, amongst a thick layer of regenerating grasses that excluded most broom seedlings. These plants were easily treated by hand pull- ing, slashing or carefully sprayed with an appropriate herbicide by ground staff. The cut and mulch control is based on the principle of removing seed producing plants before dealing with recruitment Figure 3. Picture of broom demonstration trial site showing degree of broom from the seedbank and is effective because regrowth on 1 February 1998. of specific aspects of broom biology. These are that the broom only reproduces by seed and, in the area of Waratah, only Conclusions West Coast Council and West Coast Weed flowers and sets seed between October On suitable ground the cut and mulch Strategy group also provided some and December when it is at least 40 cm tall. method described here is cost effective support. Andy Sheppard and Mark In the trial, the cut and mulch method al- and, with forward planning, will decrease Boersma are to be thanked for critically lowed approximately three years of costs of long-term broom control. It is reviewing this manuscript. breathing space between mulching and most effective when applied to a small follow up treatments that must be part of area initially. This area can be extended in References any integrated management strategy. stages. This method results in a longer pe- Chevallier, A. (1996). ‘The encyclopedia of The cut and mulch method may also be riod before broom regeneration needs to medicinal plants.’ (Dorling Kindersley applicable on a smaller scale for small be treated when compared with other me- Ltd, London). infestations using a smaller portable chanical broom control methods. This al- Hosking, J.R., Smith, J.M.B. and Sheppard, mulcher in combination with the cut lows the incorporation of biological con- A.W. (1998). Cytisus scoparius (L.) Link stump method of applying herbicide (see trol to assist in control of any untreated ssp. scoparius. In ‘The biology of Aus- Hosking et al. 1998). The cut and mulch regrowth. tralian weeds’, Volume 2, eds F.D. technique may be equally effective against Panetta, R.H. Groves and R.C.H. Shep- gorse. Acknowledgments herd, pp. 77-88. (R.G. and F.J. National Heritage Trust for operating Richardson, Melbourne). funds for this program. Waratah Landcare Launert E. (1981). ‘Country life guide to group provided support along with the edible and medicinal plants of Britain Major, General Manager and Joe Fagan and Northern Europe’. (Hamlyn Pub- from Waratah-Wynyard Council. The lishing Group Ltd., London). 186 Plant Protection Quarterly Vol.15(4) 2000 Phone: 08 8944 8420 Fax: 08 8944 8444 Email: [email protected] Role: ex-Broom Scientist France and UK Rick Roush Broom workshop participants CRC for Weed Management Systems, Waite Campus, University of Adelaide, PMB 1, Glen Osmond SA 5064. Phone: 08 8303 6591 Fax: 08 8303 7125. Email: [email protected] Role: Director CRCWMS Bev Adams Anne Heinrich Andy Sheppard PO Box 189, Scone NSW 2337 389 Playfords Road, Comboyne, NSW 2429 CSIRO Entomology, GPO Box 1700, Canberra Email: [email protected] Phone: 02 6550 4232 Fax: 02 6550 4232 ACT 2601. Phone: 02 6246 4135 Fax: 02 6246 Phone: 02 6545 0246 Fax: 02 6545 0246 Email: [email protected] 4177. Email: [email protected] Role: BTBC - Publicity Officer Role: Rare and Threatened Plants in broom Role: CSIRO/CRCWMS MCBCSB areas at Barrington Tops Ian Atkinson Mellesa Shroder Craig Hore PO Box 55, Lyons ACT 2606 National Parks and Wildlife Service, Locked Email: [email protected] Parks Victoria, PO Box 20, Bright Vic. 3741 Bag 99, Nelson Bay NSW 2315 Phone: 02 6282 7045 Fax: 02 6282 6734 Phone: 03 5755 1577 Fax: 03 5755 1176 Phone: 02 4984 8207 Fax: 02 4981 5913 Role: Nursery Industry Development Officer Email: [email protected] Email: [email protected] Chris Barnes Role: Parks Victoria Ranger for Broom Role: NPWS – Pest Species Officer BTNP North Forest Products, GPO Box 1480, Hobart John Hosking Anthony Signor Tas 7001. Phone: 03 6221 1114 Fax: 03 6221 NSW Agriculture, RMB 944, Tamworth NSW State Forests, PO Box 1, Gloucester NSW 2422 1100. Email: [email protected] 2340. Phone: 02 6763 1129 Fax: 02 6763 1222 Phone: 02 6558 1005 Fax: 02 6558 2073 Role: Weed Scientist - controlling broom in Email: [email protected] Current address: NSW Agriculture, RMB 944, native forests and eucalypt plantations Role: CRCWMS/NSW Agr, MCBCSB Tamworth NSW 2340 Kevin Carter Chris Howard Phone: 02 6763 1238 Fax: 02 6763 1222 State Forests, PO Box 692, Taree NSW 2430 National Parks and Wildlife Service, PO Box Email: [email protected] Phone: 02 6551 0074 Fax: 02 6551 2326 236, Gloucester NSW 2422 Role: Controlling broom in State Forests at Role: MCBCSB Phone: 02 6558 1478 Fax: 02 6558 2476 Barrington Tops Current address: National Parks and Wildlife Email: [email protected] Jeremy Smith Service, 78 Hargreaves Drive, Taree NSW Role: NPWS Officer, BTNP Department of Geography and Planning, 2430. Phone: 02 6552 4097 Fax: 02 6551 0575 Dennis Isaacson University of New England, Armidale NSW Email: [email protected] Oregon Department of Agriculture, 635 2351. Phone: 02 6773 2656 Fax: 02 6773 3030 Tony Clark Capitol Street, NE Salem, Oregon 97301, USA Email: [email protected] Hunter Pastoral Company, Ellerston via Scone Phone: 0011 1 503 986 4621 Role: Associate Professor at UNE, broom NSW 2337. Phone: 02 6540 7111 Fax: 02 6546 Email: [email protected] research and MCBCSB 5172. Email: [email protected] Role: Special projects officer (deals with Laurence Smith Role: Land manager – BTBC/MCBCSB broom) Oregon DA PO Box 7, Amberley, New Zealand Tim Cone Russell Knutson Phone: 0011 64 33148014 Upper Hunter Weed County Council, PO Box National Parks and Wildlife Service, PO Box Email: [email protected] 122, Muswellbrook NSW 2333 472, Tumut, NSW 2720 Role: Senior Biosecurity Officer (includes Phone: 02 6545 3428 Fax: 02 6545 3428 Phone: 02 6947 7016 Fax: 02 6947 4170 broom control) Role: Weeds Officer (Scone) Email: [email protected] Anthony Swirepik Role: at time of meeting Russell was NPWS Peter Deane CSIRO Entomology, GPO Box 1700, Canberra Manager Area Kosciusko National Park (now PO Box 91, Tallaganda Shire, Braidwood NSW ACT 2601. Phone: 02 6246 4252 Fax: 02 6246 Manager for Tantangara (South West Slopes 2622. Phone: 02 4842 2225 Fax: 02 4842 2669 4177. Email: [email protected] Region)) Email: [email protected] Role: CRCWMS biological control agent Role: Weeds Officer (Braidwood) Raelene Kwong redistribution officer Bill Dowling Keith Turnbull Research Institute, PO Box 48, Eddie Talbot PO Box 197, Dungog NSW 2420 Frankston Vic. 3199 PO Box 598, Queenstown, Tas 7467 Phone: 02 4995 9230 Fax: 02 4995 9281 Phone: 03 9785 0171 Fax: 03 9785 2007 Phone: 03 6471 2230 Fax: 03 6471 2230 Role: Rare and Threatened Plants in broom Email: [email protected] Role: Broom Control – Landcare areas at Barrington Tops Role: KTRI Ag Vic. Biocontrol services Queenstown/Waratah (at time of workshop) Paul Downey Andrew Leys Leigh Taylor CSIRO Entomology, GPO Box 1700, Canberra National Parks and Wildlife Service, PO Box 72 Cascade Street, Katoomba NSW 2780 ACT 2601. Phone: 02 6246 4253 Fax: 02 6246 1967, Hurstville NSW 2220 Phone: 02 4782 2218 4177. Email: [email protected] Phone: 02 9585 6651 Fax: 02 9585 6686 Role: Bonnie Doon Fauna Study – Blue Role: CRCWMS PhD Broom Email: [email protected] Mountains Role: NPWS Pest Species Program Leader John Fisher Mark Williams Janine Lloyd Program Leader (Weeds), NSW Agriculture, Blue Mountains City Council, PO Box 189, CRC for Weed Management Systems, Waite Locked Bag 21, Orange NSW 2800 Katoomba NSW 2780 Campus, University of Adelaide, PMB 1, Glen Current address: as above but now Progam Phone: 02 4780 5343 Fax: 02 4780 5339 Osmond SA 5064 Leader (Environmental Planning and Email: [email protected] Current address: CRC for Weed Management Management). Phone: 02 6391 3163 Fax: 6391 Role: Weeds Coordinator (Katoomba) 3767. Email: [email protected] Systems, 26/ 23 Hudson Fysh Avenue, Parap Acronyms Role: CRCWMS/NSW Agr, MCBCSB NT 0820. Phone: 08 8941 6820 CSIRO Commonwealth Scientific and Simon Fowler Email: [email protected] Role: CRCWMS Ph.D. Broom Industrial Research Organisation Private Bag 92170, Auckland, New Zealand NPWS National Parks and Wildlife Service Peter Marshall Phone: 0015 64 9 8154200 ext 7086 Fax: 0015 KTRI Keith Turnbull Research Institute PO Box 94, Braidwood NSW 2622 64 9 8497093. Email: [email protected] CRCWMS Cooperative Research Centre for Phone: 02 4842 2677 Fax: 02 4842 2950 Role: Broom Scientist UK and NZ Weed Management Systems Role: Property owner with broom Dave Grant MCBCSB Management Committee for the Hunter Pastoral Company, Ellerston via Scone Quentin Paynter Biological Control of Scotch Broom NSW 2337. Phone: 02 6546 4120 CSIRO Entomology, Tropical Ecosystems BTBC Barrington Tops Broom Council Role: Manager ‘Tomalla’ Research Centre, PMB 44, Winnellie NT 0822 BTNP Barrington Tops National Park