African Boxthorn (Lycium Ferocissimum) and Asset Protection from a National Perspective

Nineteenth Australasian Weeds Conference

African boxthorn (Lycium ferocissimum) and asset protection from a national perspective

Michael Noble1, Robin Adair2 and Alan Yen3 1 Department of Primary Industries, Parks, Water and Environment, PO Box 303, Devonport, Tasmania 7310, Australia 2 Australis Biological, PO Box 151, Bittern, Victoria 3918, Australia 3 Department of Environment and Primary Industries and School of Applied Systems Biology, La Trobe University, 5 Ring Road, Bundoora, Victoria 3083, Australia ([email protected])

Summary African boxthorn (Lycium ferocissimum fly (Bactrocera tryoni Froggatt), and potentially the Miers), a Weed of National Significance, is widespread tomato potato psyllid (Bactericera cockerelli Sulc) in southern Australia. Development of a national should it enter Australia. African boxthorn has a sig- strategy, biological control feasibility assessment, nificant presence in southern Australia’s agricultural and a national best practice manual for boxthorn led areas. to the identification of key areas to guide investment. In 2012, African boxthorn was declared a Weed of With a weed as widespread as African boxthorn National Significance (WoNS). Following WoNS dec- in Australia, asset protection is the priority for man- laration, an African boxthorn national strategic plan, agement, along with provision of additional tools for feasibility of biological control of African boxthorn management of a widespread weed. initial assessment and African boxthorn national best This paper outlines three key areas where man- practice manual have been produced. The strategic agement investment for African boxthorn in Australia plan outlines national priorities for the strategic man- might be made. These are: biodiversity-rich areas of agement of African boxthorn in Australia. Western Australia where boxthorn has significant Widespread weeds like boxthorn can be difficult invasive potential; horticultural regions susceptible to direct expenditure toward, as priorities are often to pest species hosted by boxthorn; and boxthorn difficult to pinpoint. Using the biosecurity continuum biocontrol research. (AWC 2013), asset protection and building manage- Keywords African boxthorn, Weeds of National ment capability are logical investment approaches Significance, biodiversity, horticulture, biological for African boxthorn in much of southern Australia. control. This paper looks at three specific areas of importance for the national management of African INTRODUCTION boxthorn. These are the ongoing expansion and impact African boxthorn has been present in Australia for potential of African boxthorn in ecologically rich more than 150 years and is one of Australia’s most southern Western Australia, the potential of African widespread weeds. It occurs across a diverse range of boxthorn as a host for horticultural pests in areas Australian landscapes from coastal to semi-arid inland with solanaceous crops, and the potential of classical habitats, and is present in many of Australia’s most biological control to provide an additional African important environmental and agricultural asset areas. boxthorn management tool. In Australia, boxthorn impacts World Heritage listed places (e.g. Shark Bay in Western Australia and WESTERN AUSTRALIAN LANDSCAPES the Lord Howe Island Group in New South Wales), In Western Australia, unlike most other suitable parts Ramsar-listed wetlands (e.g. Pitt Water – Orielton La- of Australia, African boxthorn has not fully expanded goon in Tasmania and the Coorong in South Australia), throughout its potential range. This may be linked to internationally and nationally recognised biodiversity the relationship between boxthorn and the starling hotspots, and many of the nation’s most significant (Sturnus vulgaris). Evidence from Bass Strait (Harris offshore island environments. and McKenny 1999) and New Zealand (Taylor 1968) African boxthorn hosts a range of pest animals suggests that starlings boost boxthorn’s capacity to including rabbits (Oryctolagus cuniculus Linnaeus), invade natural environments, and in turn, boxthorn foxes (Vulpes vulpes Linnaeus), feral pigs (Sus scrofa provides quality roosting and feeding habitat for Linnaeus), starlings (Sturnus vulgaris Linnaeus), fruit starlings. The pest species’ appear to have facilitative

231 Nineteenth Australasian Weeds Conference interactions. The starling is so far absent (other than reaching Australia in the near future. In North America, occasional incursions) from Western Australia. its overwintering host plants are several native Lycium The virtual absence of starlings in Western species (Butler and Trumble 2012). The TPP is a major Australia permits greater potential for containment pest of solanaceous crops such as tomatoes, potatoes, of boxthorn, so far preventing it from establishing a capsicum, egg plants and tamarillos because it is the foothold throughout important natural assets, despite vector of the plant bacteria, Candidatus Liberibacter being present around them. solanacearum Jagoueix et al., the causative agent of The establishment of starlings in Western Australia the so-called zebra chip disease. would almost certainly result in increased invasive The TPP is reputed to have over 40 host plant spe- capacity of boxthorn in natural ecosystems. cies, primarily in the Solanaceae family (Biosecurity Western Australia has substantial environmental Australia 2009). It was recently found to use African assets of national and global significance. In the south- boxthorn as an overwintering host plant (Fowler 2013), ern half of the state, boxthorn poses a direct threat to and is able to breed on that host species (J. Dohmen, some of these. For example, on the South Coast the Fitz- pers. comm. 2013). TPP populations build up on their gerald River Ravensthorpe region provides habitat for over wintering hosts, and they colonise commercial an extraordinary number of nationally listed threatened crops in spring. The sizes of TPP populations can be species (more than 40 species of fauna and over 100 reduced if access to overwintering host plant species flora species) (Gilfillan et al. 2009). The area holds a is reduced; hence the importance of controlling Af- United Nations designation of ‘Fitzgerald Biosphere’, rican boxthorn near susceptible horticultural crops. containing two internationally listed wetlands, and Another danger is the possible transfer of Candidatus having immense overall species richness – making it Liberibacter solanacearum to native Australian plant a biodiversity hotspot. species by any native Australian psyllids that may feed The presence of African boxthorn on off-shore on plants with this disease. Acizzia solanicola Kent & islands in Western Australia appears to be increasing. Taylor is a native Australian psyllid that has switched African boxthorn continues to threaten, for example, from its native solanaceous plant species to egg plants Australian sea lion (Neophoca cinerea Peron) and (Taylor and Kent 2013). Australian fur seal (Arctocephalus pusillus Schreber) breeding habitats through displacing the native nitre BIOLOGICAL CONTROL bush (Nitraria billardieri DC.) that shelter sea lion and African boxthorn is difficult to suppress using seal pups. Boxthorn does not provide the equivalent mechanical and chemical control methods due to a quality of nursery habitat to that provided by nitre persistent seed bank, strong re-colonisation capacity bush, leaving pups more vulnerable to predation and expense. Although African boxthorn has been sug- (Moritz and Kikkawa 1994). gested as a target for biological control (Julien 2006), In 2013 Western Australia’s South Coast NRM Australia is the only region where this approach is completed a substantial African boxthorn management being considered. In 2013, the potential for biological program. Other Western Australian initiatives have control was formally evaluated and considered to be included the state’s Department of Parks and Wildlife feasible (Adair 2013). recent undertaking of African boxthorn management In Australia, a low diversity and abundance of on the Beagle Islands south of Geraldton. These islands natural enemies from African boxthorn are known. provide some of the most important sea lion breeding In a recent survey, only 12 species of arthropod and habitat on the Western Australian coastline. pathogen were recorded from south-eastern Australia, Follow-up of initial boxthorn control measures is but it is likely additional taxa could be recorded with essential to successful management. It is very impor- more extensive searches. tant that ongoing investment be made to continue and Similarly, in southern Africa, only five arthropods extend this strategically important work in Western and one pathogen are recorded from L. ferocissimum, Australia. but a richer assemblage is known from other Lycium species elsewhere indicating that the low diversity is IMPLICATIONS FOR HORTICULTURE perhaps an artefact of limited survey and collection Boxthorn hosts a range of agricultural pests including effort in the region of origin. Biological surveys on the fruit fly (Bactrocera tryoni) and the tomato potato other large, woody African shrubs (e.g. boneseed psyllid (TPP) (Bactericera cockerelli). The latter is Chrysanthemoides monilifera subsp. monilifera (L.) a North America species that has spread to Central Norlindh and myrtle-leaf milkwort Polygala myrti- America (Davidson et al. 2008). It has not been found foilia L.), show a richer assemblage of phytophagous in Australia yet, but there is a very high risk of it arthropods. Further survey effort in both Australia

232 Nineteenth Australasian Weeds Conference and southern Africa is required on African boxthorn step though requires research funding to progress the to fully evaluate its phytophagous biota (Adair 2013). assessment of this rust for introduction into Australia. Despite these limitations, four of the species re- These three areas represent priority environmen- corded from L. ferocissimum in South Africa appear tal and agricultural asset protection and improved to be monophagous and have potential as classical management capability investment opportunities for biological control agents for African boxthorn. These African boxthorn management in Australia. are the tortoise beetles Cassida lycii Borowiec & Swi- etojanska, C. ditinguenda Spaeth, C. melanophthalma REFERENCES Boheman, and the pathogen Puccinia rapipes R.Berndt Adair, R. (2013). Feasibility of biological control of and E.Uhlmann. African boxthorn (Lycium ferocissimum). Unpub- Puccinia rapipes (boxthorn rust) has consider- lished report. (Department of Primary Industries, able potential as a biological control in Australia as Parks, Water and Environment, Devonport, Tas- most rusts have highly restricted host ranges, can be mania). highly damaging to their hosts and are generally easy Australian Weeds Committee (AWC) (2013). Weeds of to collect and establish in the laboratory or field. It is National Significance African Boxthorn (Lycium highly likely other damaging pathogens also occur ferocissimum) Strategic Plan. (Australian Weeds on African boxthorn in southern Africa, but remain Committee, Canberra). unrecorded due the absence of systematic survey ef- Biosecurity Australia (2009). Final pest risk analysis fort (Adair 2013). report for ‘Candidatus Liberibacter psyllaurous’ Although Lycium is taxonomically isolated from in fresh fruit, potato tubers, nursery stock and its the majority of other Solanaceae in Australia, the vector the tomato-potato psyllid. (Biosecurity native shrub L. australe F.Muell. is closely related Australia, Canberra). and is a key species for consideration in future host Butler, C.D. and Trumble, J.T. (2012). The potato psyl- specificity evaluation, should it occur. lid, Bactericera cockerelli (Sulc) (Hemiptera: Tri- ozidae): life history, relationship to plant diseases, DISCUSSION and management strategies. Terrestrial Arthropod The 2012 Weeds of National Significance declaration Reviews 5(2), 87-111. and Australian Government coordination investment Davidson, M.M., Teulon, D.A.J., Scott, I.A.W. and allowed a first national overview of African boxthorn Workman, P. (2008). A review of the potato psyl- in Australia. Coming from that overview were several lid (Bactericera cockerelli); a new insect pest of key national management priorities that have been potato in New Zealand. Crop and Food Research elaborated upon here. Report No 2231. From a natural environment perspective, a stra- Fowler, S. (2013). What do zebra chips have to do with tegically important expenditure on African boxthorn broom biocontrol? What’s new in the biological management is Western Australia’s high value envi- control of weeds? Issue 64, 6-7. ronmental assets (e.g. the Fitzgerald River biosphere Gilfillan, S., Mitchell, P., Newell J., Danks, A. and and offshore islands). Should starlings establish in Comer, S. (2009). South Coast threatened species Western Australia, boxthorn infestations will extend and ecological communities regional strategic into natural areas where they have not yet achieved management plan. (Department of Environment a foothold. and Conservation, Albany, Western Australia). There is a strong potential for tomato potato psyl- http://www.conservation.wa.gov.au/media/14355/ lid (Bactericera cockerelli) to arrive in Australia, and ref%207%20gilfillian_etal_2009_scregionaltsp- use of boxthorn by it for overwintering. An assess- lan.pdf (accessed 21 May 2014). ment of solanaceous cropping areas and comparison Harris, S. and McKenny, H. (1999). Preservation of boxthorn infestation areas is recommended. This Island, Furneaux Group: two hundred years of would assist biosecurity staff, industry and others to vegetation change. Papers and Proceedings of the determine priorities and undertake strategic action. Royal Society of Tasmania 133(1). From a broader perspective, investment in devel- Julien, M.H. (2006). Biological control of rangeland opment of an African boxthorn biological control agent weeds in Australia. Rangeland Journal 28, 47-54. is strongly warranted, having the potential to reduce Moritz, C. and Kikkawa, J. (1994). Conservation the weed’s impact across its existing range. Initial biology in Australia and Oceania. (Surrey Beatty, research (Adair 2013) has indicated strong potential Chipping Norton, New South Wales). for boxthorn biocontrols. The potential of the rust spe- Noble, M. and Rose, M. (2013). African boxthorn cies Puccinia rapipes particularly stands out. The next national best practice manual – managing African

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boxthorn (Lycium ferocissimum) in Australia. first record from New Zealand of Acizzia solani- (Department of Primary Industries, Parks, Water cola (Hemiptera: Psyllidae). Zootaxa 3613(3), and Environment, Hobart). 257-73. Taylor, G.S. and Kent, D.S. (2013). Potential eco- Taylor, R.H. (1968). Introduced mammals and islands: nomic pests of solanaceous crops: a new species priorities for conservation and research. Proceed- of Solanum-feeding psyllid from Australia and ings of the New Zealand Ecological Society 15.

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