172 Plant Protection Quarterly Vol.16(4) 2001 and added to the suite of potential agents (Grosskopf 1996). Predicting the likely success of biological control of First-instar larvae of O. pilosellae hatch hawkweeds in New Zealand after 2–3 weeks, and over winter at this stage, or rarely as second-instar larvae. In

A A B A spring, larvae are found in a loose web Pauline Syrett , Lindsay Smith , Gitta Grosskopf and Colin Meurk at the centre of the rosette crown. By feed- A Landcare Research, PO Box 69, Lincoln, Canterbury, New Zealand. ing at the growing points, larvae deform B CABI Bioscience, 1 chemin des Grillons, Delémont, Switzerland. and severely stunt the growth of leaves and stolons. Flowering is reduced, and heavily infested rosettes may die. Levels Summary of parasitism of up to 35% in field- Five species of hawkweed (Hieracium strain of the rust so two further strains collected larvae of O. pilosellae have been pilosella, H. praealtum, H. caespitosum, have been imported for widespread observed in Europe (Grosskopf 1997). The H. aurantiacum and H. lepidulum), origi- release (T.A. Jenkins, personal communi- gall wasp, A. subterminalis, is partheno- nating from Europe, are invasive in na- cation). genic and only females are produced. tive grassland ecosystems in New Zea- Five of the nine adventive Hieracium Eggs are laid into stolon tips, and larvae land, displacing desirable environmen- species in New Zealand are regarded as develop within the tip, inducing forma- tal and agricultural species. A rust fun- problem weeds: H. pilosella L. (mouse-ear tion of a gall. The wasp larvae spend win- gus and five insect species have been hawkweed) is the most widely estab- ter inside the galls, pupating in spring so identified for introduction as comple- lished, and has been in New Zealand the that new-generation adult wasps emerge mentary biological control agents. The longest, since 1878; H. praealtum Gochnat in early summer. Stolons infested with rust fungus Puccinia hieracii var. (king devil) is also widespread, but less gall wasps produce deformed daughter piloselloidarum is now widely estab- abundant; while H. caespitosum Dumort. rosettes, or form galls instead of new lished as the result of an accidental intro- (field hawkweed) and H. lepidulum plants. Plant nutrients are diverted from duction, but attacks only some forms of (Stenstr.) Omang (tussock hawkweed) are forming daughter rosettes to producing H. pilosella. Two insect species, a plume more recent arrivals (1940 and 1946 re- galls so that vegetative reproduction may moth, Oxyptilus pilosellae, and a gall spectively) with more limited distribu- be severely impeded (Grosskopf 1995, wasp, Aulacidea subterminalis, have al- tions (Webb et al. 1988). Hieracium aurant- 1996). ready been released in the field, and two iacum L. (orange hawkweed) has only re- The predicted host range of the five in- syrphid flies (Cheilosia urbana and C. cently been regarded as weedy in New sect species to be established in New Zea- psilophthalma), and a gall midge Zealand, although it has been here since land was determined experimentally, and (Macrolabis pilosellae) are expected to be 1911 and is also a problem weed in North from these data, and the known feeding released shortly. The six control agents America (Wilson et al. 1997). behaviour of the species, possible com- should complement each other because A survey was conducted throughout parative levels of damage to weedy Hier- they attack different parts of the plant, the Hieracium-infested areas of New Zea- acium species were predicted. A simula- and between them are predicted to affect land (Figure 1) for insects feeding on these tion experiment was conducted to meas- all five weedy hawkweeds. All six agents plants with the aim of identifying phy- ure the impact of two levels of depression are likely to achieve significant levels of tophagous species that were already caus- of Hieracium species on vegetation compo- damage on H. pilosella, three of them ing damage (Syrett and Smith 1998). Sev- sition of hawkweed-infested grassland. will target H. praealtum, four of them enty six species of native and exotic insects The field release of two species, O. pilo- should suppress H. caespitosum and H. were found, including both polyphagous sellae and A. subterminalis, has been ap- aurantiacum. Only one insect species, and oligophagous species, but there were proved, but the outcome of an application the root-feeding C. urbana, is predicted none of the specialist European Hieracium- for release of the other three insects is still to be as damaging to H. lepidulum as to feeding insects. There were no species awaited. A summary of the host range H. pilosella, so further control agents are causing significant damage that would testing, preliminary results from the simu- likely to be needed to suppress this non- make the introduction of any potential lation experiment, and rearing and release stoloniferous hawkweed. biological control agent redundant. of O. pilosellae and A. subterminalis are re- Surveys were conducted in Europe to ported here. Introduction identify those host-specific insects that A biological control programme for had potential for introduction into New Methods Hieracium spp. (Asteraceae) (hawkweeds) Zealand as biological control agents for Host specificity tests was initiated in 1992 because the invasive- Hieracium species (Jordan 1993, Syrett and A similar number of plant species were ness of this group of plants was identified Sárospataki 1993). Four species were se- selected for host specificity tests with all as an important factor contributing to the lected for further study: a plume moth, five insects. They included all Hieracium desertification of large areas of tussock Oxyptilus pilosellae Zeller (Pterophoridae), species naturalized in New Zealand (ex- grassland in the South Island hill- and whose larvae feed in the crown of the ro- cept H. pollichiae Schulz.-Bip.), from both high-country of New Zealand (Syrett et al. sette plant; Aulacidea subterminalis Niblett subgenera Pilosella and Hieracium, species 1996). Representatives of both subgenera (Cynipidae), which galls stolons; Cheilosia chosen from other genera in the tribe Pilosella (stoloniferous) and Hieracii (non- urbana (Meigen) (= C. praecox (Zetterstedt)) Lactuceae (including native New Zealand stoloniferous) species are invasive in New (Syrphidae), which feeds externally on species that would not previously have Zealand. One possible biological control roots; and Macrolabis pilosellae (Binnie) been exposed to the insects), economically agent, a strain of the rust fungus Puccinia (Cecidomyiidae), which produces galls on important members of other tribes in the hieracii (Röhl.) H.Mart. var. piloselloidarum leaves and stems as well as at stolon tips family Asteraceae, and a selection of more (Probst) Jørst., was accidentally intro- (Grosskopf 1995, 1996). A further Hieracium- distantly related representatives of fami- duced and has established in New Zea- feeding syrphid, Cheilosia psilophthalma lies containing important cultivated plants land on H. pilosella (Morin and Syrett (Becker), that feeds on the above-ground and native New Zealand plants. Host 1996). Not all H. pilosella plants in New parts of the plant and complements the plants of close relatives of the proposed Zealand appear to be susceptible to this activity of C. urbana, was later identified, biological control agents were also Plant Protection Quarterly Vol.16(4) 2001 173 included. Tests were conducted by CABI N Bioscience at Delémont, Switzerland, and under containment by Landcare Research at Lincoln. No-choice larval feeding and develop- ment tests, single-choice larval feeding tests, and multiple-choice oviposition tests were conducted with the plume moth, O. pilosellae (Syrett et al. 1997). Larval devel- opment tests were carried out on potted Auckland plants. Pots were embedded in the ground, covered with individual gauze bags, and examined after 10 months when all stages of the plume moth were retrieved. For the gall wasp, A. subterminalis, all the tests were combined oviposition and larval development tests, because once the egg has been placed by the female wasp, the larva hatches and feeds inside the de- veloping gall, and is unable to transfer to another feeding site or host plant (Syrett et al. 1998). Oviposition was induced in gauze cages containing four randomly al- located test plants with a single H. pilosella Wellington plant. Female wasps were released into each cage for four days. When gall devel- 1 2 opment was complete, numbers of galls, 4 3 adult wasps, and parasitoids were re- 5 6 corded. All ungalled plants were dis- sected to identify eggs or immature stages of the wasp. 7 No-choice development tests, and sin- 9 8 Christchurch gle-choice oviposition tests, were carried 10 out both with the root-feeding hover fly, 11 12 13 C. urbana, and the crown-feeding hover 16 17 S 14 fly, C. psilophthalma. An open field test was 18 M 19 15 also carried out with C. urbana. In no- L choice larval development tests newly 21 20 22 emerged larvae were transferred into leaf 23 axils of each test plant. Plants were indi- 24 25 26 27 vidually caged in gauze bags for several Dunedin 28 days until larvae had established them- 29 selves in an appropriate feeding site. Pot- ted plants were then embedded in soil, and maintained for four months when all pots were checked for the presence of lar- Areas of major infestation of Hieracium species vae. Larvae were extracted, and placed in- Release sites dividually in vials with soil until they pu- pated. Numbers pupating successfully, and numbers of adults emerging the fol- lowing spring, were recorded. Figure 1. Distribution of weedy Hieracium species (hawkweeds) in New For the tests with the gall midge, M. Zealand, and sites where the biological control agents O. pilosellae and pilosellae, newly emerged female flies were A. subterminalis have been released. placed with male flies within a gauze bag covering each test plant. Plants were Gall wasp release sites: 1 = Muller, 2* = Molesworth, 3* = Molesworth, checked weekly for signs of gall develop- 4 = Molesworth, 5 = Molesworth, 6* = Molesworth, 7 = Castle Hill, ment, and once this was observed, plants 8* = Castle Hill, 9 = Ryton, 10 = Clent Hills, 11 = Balmoral, 12 = Balmoral, were placed in gauze cages. Adults were 13 = Glenrock, 14* = Grampians, 15 = Stoney Creek, 16 = Ben Ohau, collected and counted as they emerged. 17 = Ben Avon, 18* = Ben Avon, 19 = Geordie Hills, 20* = Geordie Hills, Simulated biological control of hawkweed 21 = Mt. Pisa, 22 = Michael’s Peak, 23 = Nokomai, 24 = Nokomai, In 1993 three study sites were selected 25 = Mt. Nicholas, 26 = Lorn Peak, 27 = Goulburn, 28* = Goulburn, in hawkweed-infested regions of the 29 = Mt. Linton Stations. South Island: a tall-tussock community *sites where galled plants were planted out. (Chionochloa rubra grassland, with bare ground, and invading H. pilosella, H. Plume moth release site: 13 = Glenrock Station. praealtum, and H. lepidulum) at Lindis Pass; a short-tussock community (Festuca novae- Simulated biological control experimental sites: S = Sawdon Station, zelandiae with native turf grasses and M = Maryburn Station, and L = Lindis Pass Reserve. 174 Plant Protection Quarterly Vol.16(4) 2001 herbs, some matagouri (Discaria toumatou) galls were harvested and placed into an outside the genus were not attacked. In and invading H. pilosella, H. praealtum, and artificial winter for 5–6 months, and the single-choice oviposition tests eggs were H. caespitosum) at Maryburn Station in rest left to develop naturally on the plant laid on all Hieracium species, but not on the Mackenzie Basin; and a severely de- in a shade house under winter/spring any of the other test plants. Very few lar- graded site (sparse F. novae-zelandiae, na- conditions. The first two field releases, vae established in the open field test, and tive herbs and turf grasses, with extensive each of 100 adult wasps, were made on 11 most were on H. aurantiacum, H. praealtum cover of H. pilosella and substantial February 1999 on Balmoral and Glenrock and H. pilosella. A proportion of all above amounts of bare ground) at Sawdon Sta- Stations, in the Mackenzie Basin. A further ground-feeding hover fly larvae, C. psilo- tion (Figure 1). In order to reduce variabil- 27 releases were made at sites throughout phthalma, developed to adult on all ity in the results sub-plots were selected the South Island between November 1999 Hieracium species in no-choice larval de- within each treatment plot so that hawk- and February 2000 (Figure 1). Eighteen re- velopment tests (Table 4). No larvae, pu- weed cover was in the range 40–60%. Two leases comprised 80–150 adult wasps, and pae, or feeding marks were found on any treatments were used to suppress hawk- nine consisted of 3–6 plants bearing a total test plants outside the genus. Fewer larvae weeds: glyphosate herbicide was hand- of 15–40 galls. The plants were grown in developed on non-stoloniferous Hieracium painted onto all, or 50%, of hawkweed pots and transplanted in the field. species (Table 4). leaves and stolons in each treatment sub- Gall development, and emergence of plot. Treatment sub-plots were small (0.1 Results new-generation adult gall midges of M. × 0.1 m) so that 50 and 100% suppression Host specificity tests pilosellae occurred only on Hieracium spe- represented a realistic simulation of effec- Normal larval feeding by the plume moth, cies within the sub-genus Pilosella. Two tive biological control at this scale. We re- O. pilosellae, was observed only on plants species within this group, H. aurantiacum applied the treatments as necessary to within the genus Hieracium, and H. and H. × stoloniflorum, were unacceptable maintain hawkweed cover at 0 and 50% of pilosella was preferred over other Hiera- hosts in tests (Table 5). initial levels respectively. Visual estimates cium species (Table 1). In no-choice feed- From results of the host range tests, of vegetation type and cover in treatment ing tests a small number of late-instar lar- summarized here from Grosskopf (1996, sub-plots and control plots were made vae were able to complete development on 1997) and Grosskopf and Hassler (1998), once a year from 1993 to 1999 by a single the New Zealand native plants Sonchus the host range of all five insect species was skilled observer (C.M.). The 1993 meas- kirkii and Embergeria grandifolia (Lactu- predicted (Table 6). urements were taken before the treat- ceae), but in single-choice feeding tests ments were applied. these plants were less preferred than H. Simulated biological control of hawkweed pilosella. Preliminary analyses were conducted us- Rearing and release of O. pilosellae and Galls of A. subterminalis were produced ing data averaged over all three sites. A. subterminalis on plants of H. pilosella and H. aurantiacum, Except for 1993 (prior to treatment), the Up to 20 newly emerged adult moths of O. but not on any other plant species. Wasps treatment plots showed a significant in- pilosellae were placed with eight-potted H. developed through to adult on both H. crease in bare ground and litter (P<0.001) pilosella plants in a clear plastic box within pilosella and H. aurantiacum (Table 2). over the controls. This was not surprising a controlled-temperature room under In no-choice larval development tests since treatments were designed to remove long days and moderate temperatures. larvae of the root feeding hover fly, C. ur- a substantial proportion of vegetation, Moths were provided with a bouquet of bana, were found on all Hieracium species and removed hawkweed was not rapidly nectar-producing flowers, cotton wool except H. murorum (Table 3), but plants replaced by other plants. Some 100% soaked in a dilute solution of honey-water, and pollen as a food source. A second method was tested in which moths were Table 1. Acceptability of Hieracium spp. to Oxyptilus pilosellae in no-choice transferred to polyester fibre mesh cages larval development tests conducted in Switzerland. maintained in a glasshouse where they Hieracium species No. L1A larvae placed on plants % larvae developed to adult were subjected to natural daylight. They were provided with similar food sources. Sub-genus Pilosella Eggs were left on the potted plants so that H. pilosella EUR 195 27.2 emerging larvae would search out suitable H. pilosella NZ 72 38.9 over-wintering sites on the undersides of H. aurantiacum 70 7.1 leaves. Plants were maintained through H. caespitosum EUR 65 4.6 the winter, so that larvae continued their H. caespitosum USA 40 20.0 development in the spring, and new- H. praealtum 68 2.9 generation adult moths emerged from Sub-genus Hieracium cocooned pupae on the underside of H. lepidulum 70 5.7 leaves. The first field release, of 32 adult H. murorum 60 1.7 moths, was made on 26 March 1999 at H. sabaudum 70 5.7 Glenrock Station in the Mackenzie Basin. A First-instar larvae. Adult gall wasps (A. subterminalis), newly emerged from galls, were placed Table 2. Acceptability of Hieracium pilosella and H. aurantiacum to with potted H. pilosella plants in either clear plastic boxes or polyester fibre mesh Aulacidea subterminalis (Cynipidae) in multi-choice oviposition and larval cages in either controlled-temperature development tests conducted in Switzerland. rooms under artificial lighting, or in a Plant species No. plants % plants No. galls/ No. wasps/ No. para- % glasshouse. Cotton wool soaked in a di- offered attacked plant plant sitoids/ developed lute solution of honey-water and pollen plant to adult was provided as food for the wasps. H. pilosella EUR 76 97 9.1 4.4 2.3 81 Hawkweed plants with developing galls H. pilosella NZ 14 71 11.0 8.1 2.4 77 were maintained under spring/summer H. aurantiacum 4 50 15.5 12.5 2.5 88 conditions for 3–4 months, when some Plant Protection Quarterly Vol.16(4) 2001 175 treated plots had less than 50% vegetation However, from 1996 to 1998 vegetation Rearing and release of O. pilosellae and cover one year after treatment. From 1993 cover excluding hawkweeds was 10–30% A. subterminalis to 1995 there was significantly higher higher in treated plots than in control Plume moths did not oviposit in cages un- cover of vegetation excluding hawkweeds plots, although these differences were not der artificial lighting. Under glasshouse in control plots than in treated plots significant. The levels of vegetation cover conditions, eggs were found on the fine (P<0.001 for all three years). This occurred excluding hawkweeds for both 50% and hairs on the upper side of H. pilosella because treatment plots were not ran- 100% treatments increased with time, leaves. Small numbers of hatching larvae domly selected, and had higher initial while values for control plots did not developed through to adult, allowing one levels of hawkweed than the controls. change significantly. field release to be made, but this insect has proved difficult to rear under artificial Table 3. Acceptability of Hieracium species to Cheilosia urbana (Syrphidae) conditions and further work is required to in no-choice larval development tests conducted in Switzerland. develop a successful method. No larvae,

A or new-generation adult moths, have yet Test plant species No. of L1 % developed % developed % developed been recovered from the field. Gall wasps transferred to mature larvae to pupae to adult oviposited successfully under all condi- Sub-genus Pilosella tions, and females survived for up to 14 H. pilosella EUR 160 63 54 50 days. Oviposition scars, usually on the H. pilosella NZ 45 56 44 44 underside of stolons, a few millimetres H. aurantiacum 30 70 63 60 from the stolon tip, were apparent after H. caespitosum EUR 35 57 54 46 3–4 days. Gall formation was apparent af- H. caespitosum NZ 35 57 54 43 ter 2–3 weeks, as the stolons began to H. caespitosum USA 30 87 83 80 swell. Not all oviposition attempts led to H. praealtum 35 57 49 46 gall development. Galls were recovered H. × stoloniflorum 50 28 16 12 from two of the six sites checked in April Sub-genus Hieracium 2000; the remaining sites will be checked H. argillaceum 40 13 2.5 2.5 in 2001. H. lepidulum 30 53 40 33 H. murorum 40 – – – Discussion H. sabaudum 30 47 40 40 The rust fungus P. hieracii var. piloselloid- arum is widely established on H. pilosella A First instar larvae. in New Zealand, and is often conspicuous in spring and autumn (T.A. Jenkins, per- Table 4. Acceptability of Hieracium species to Cheilosia psilophthalma sonal communication). Two insects (O. (Syrphidae) in no-choice larval development tests conducted in pilosellae and A. subterminalis) have al- Switzerland. ready been released and galls of the latter Test plant species No. of L1A % developed % developed % developed have established under natural condi- transferred to mature larvae to pupae to adult tions. In the simulated biological control trial, preliminary indications are that Sub-genus Pilosella when hawkweeds are suppressed, they H. pilosella EUR 95 35 30 23 are replaced only slowly by other species. H. pilosella NZ 30 33 33 33 Vegetation other than hawkweeds in- H. aurantiacum 65 45 43 42 creased over time in hawkweed sup- H. caespitosum EUR 25 36 36 36 pressed plots, while that in the control H. caespitosum NZ 20 25 20 15 plots remained relatively stable. Increases H. caespitosum USA 25 48 40 32 in hawkweed are believed to be a result of H. praealtum 50 44 44 42 natural invasion facilitated by manage- H. × stoloniflorum 30 33 33 33 ment practices (Johnstone et al. 1999), al- Sub-genus Hieracium though others have suggested they in- H. argillaceum 30 3 3 3 crease only in degraded systems (Tres- H. lepidulum 60 5 3 2 konova 1992). If introduced biological H. murorum 45 9 9 4 control agents suppress hawkweeds effec- H. sabaudum 45 16 13 11 tively they may be replaced by more de- A First instar larvae. sirable vegetation. Observations in Europe showed that Table 5. Acceptability of stoloniferous Hieracium species (sub-genus both the insect biological control agents Pilosella) to Macrolabis pilosellae (Cecidomyiidae) in combined no-choice released in New Zealand have potential to suppress some species of hawkweeds oviposition and larval development tests conducted in Switzerland. (Grosskopf, personal observation). Al- Test plant species Number of Number of though the plume moth has not been Number of plants (sub-genus Pilosella) female flies adult flies found on species of Hieracium other than offered produced galls incubated emerged H. pilosella in Europe, host tests indicated that it might attack two of the weedy spe- Hieracium pilosella EUR 38 36 105 417 cies (H. caespitosum and H. lepidulum) es- H. pilosella NZ 11 9 33 114 tablished in New Zealand (Table 1). From H. aurantiacum 12 0 34 0 life cycle information reported in Europe H. caespitosum EUR 6 6 17 124 (Grosskopf 1995, Syrett et al. 1997) we pre- H. caespitosum USA 6 6 15 53 dict that plume moth eggs will be found H. praealtum 6 5 16 27 on H. pilosella in the field in New Zealand H. × stoloniflorum 12 2 36 0 from January to March. Because there are 176 Plant Protection Quarterly Vol.16(4) 2001 Table 6. Predicted level of attack on five weedy species of Hieracium by one pathogen, and five insect, biological control agents. Hawkweed species Puccinia hieracii Oxyptilus Aulacidea Cheilosia Cheilosia Macrolabis var. piloselloidarum pilosellae subterminalis urbana psilophthalma pilosellae H. pilosella ✓✓ ✓✓ ✓✓ ✓✓ ✓✓ ✓✓ H. praealtum – ✓ – ✓✓ ✓✓ ✓✓ H. caespitosum – ✓✓ – ✓✓ ✓✓ ✓✓ H. aurantiacum – ✓ ✓✓✓✓✓✓ – H. lepidulum – ✓ – ✓✓ ✓ – ✓✓ equivalent level of attack to that on H. pilosella. ✓ minor level of attack compared to that on H. pilosella. no specialized pterophorid parasitoids in C09805, and by the Hieracium Control Syrett, P. and Smith, L.A. (1998). The in- New Zealand, it is likely that these moths Trust. We are particularly grateful to the sect fauna of four weedy Hieracium may attain higher populations here (Syrett chairman of the trust, John Aspinall, and (Asteraceae) species in New Zealand. et al. 1997). Provided rearing problems can trustee Allan Innes, for their continuing New Zealand Journal of Zoology 25, 73-83. be surmounted, we expect that O. pilosellae enthusiastic support of the hawkweed Syrett, P., Smith, L.A. and Grosskopf, G. will establish throughout the range of H. biological control programme. The manu- (1997). Introduction of Oxyptilus pilo- pilosella in New Zealand, but may be ad- script benefited from comments by Jane sellae (Lepidoptera: Pterophoridae) into versely affected in areas subject to sum- Fröhlich, Peter McGregor and two anony- New Zealand for biological control of mer drought. mous referees. Hieracium pilosella. Unpublished report, In Europe galls of the wasp A. sub- Landcare Research, Lincoln, New Zea- terminalis have been recorded only from References land. H. pilosella (Syrett et al. 1998), but labora- Grosskopf, G. et al. (1995–8). Investiga- Syrett, P., Smith, L.A. and Grosskopf, G. tory host tests showed that it could per- tions on potential biological control (1998). Introduction of Aulacidea sub- form equally well on H. aurantiacum. agents of mouse-ear hawkweed, terminalis (Hymenoptera: Cynipidae) Newly developing galls should be found Hieracium pilosella L. Annual Reports, into New Zealand for biological control in New Zealand from late January on- International Institute of Biological of Hieracium pilosella. Unpublished re- wards. Rates of parasitism of 36% have Control, Delémont, Switzerland. port, Landcare Research, Lincoln, New been observed in Europe, indicating that Johnstone, P.D., Wilson, J.B. and Bremner, Zealand. wasps may also attain higher populations A.G. (1999). Change in Hieracium Treskonova, M. (1992). Inconsistencies be- here in New Zealand. There are no native populations in Eastern Otago over the tween the scale of the hawkweed New Zealand cynipid wasps, so special- period 1982–1992. New Zealand Journal (Hieracium) problem and the methods ized parasitoids are also absent. We pre- of Ecology 23, 31-8. used to investigate it. Vegetation dict that A. subterminalis should establish Jordan, T. (1993). Investigations on poten- change in tussock grasslands, with em- throughout the ranges of H. pilosella and tial biological control agents of mouse- phasis on hawkweeds. Occasional Pub- H. aurantiacum in New Zealand, but ear hawkweed, Hieracium pilosella L., in lication No 2, New Zealand Ecological populations may be limited under condi- Europe. Report, International Institute Society, Christchurch, New Zealand, tions when plants produce few stolons. of Biological Control, Delémont, Swit- eds G.G. Hunter, C.R. Mason and D.M. We expect that these two insects, to- zerland. Robertson, p. 12. gether with the already established rust Morin, L. and Syrett, P. (1996). Prospects Webb, C.J., Sykes, W.R. and Garnock- fungus, may significantly reduce the for biological control of Hieracium Jones, P.J. (1988). ‘Flora of New Zea- spread and impact of H. pilosella, and per- pilosella with the rust Puccinia hieracii land, Volume IV, Naturalised Pterido- haps have some impact on H. caespitosum var. piloselloidarum in New Zealand. phytes, Gymnosperms, Dicotyledons’. and H. aurantiacum. Three other insects Proceedings of the IX International (Botany Division, DSIR, Christchurch, still under study, C. urbana, C. psilo- Symposium on Biological Control of New Zealand). phthalma, and M. pilosellae, should comple- Weeds, 19–26 January 1996, Stellen- Wilson, L.M., McCaffrey, J.P., Quimby, ment the activity of the two already re- bosch, South Africa, University of Cape P.C. and Birdsall, J.L. (1997). Hawk- leased because, apart from attacking dif- Town, eds V.C. Moran and J.H. Hoff- weeds in the Northwestern United ferent parts of the plant, and exerting pres- mann, pp. 199-204 . States. Rangelands 19, 18-23. sure at different times in the season, host Syrett, P., Harman, H.M., Grosskopf, G. range tests indicate that they will feed on and Smith, L.A. (1996). Insects for bio- a broader range of Hieracium species (Ta- logical control of hieracium in New ble 6). However, it is likely that further Zealand: a progress report. Proceed- agents will be needed to suppress the non- ings of the IX International Symposium stoloniferous H. lepidulum. on Biological Control of Weeds, 19–26 January 1996, Stellenbosch, South Af- Acknowledgments rica, University of Cape Town, eds We thank Chris Frampton and Ray V.C. Moran and J.H. Hoffmann, pp. Webster for assistance with experimental 213-8. design and statistical analysis of the simu- Syrett, P. and Sárospataki, M. (1993). Pros- lated biological control experiment, and pects for biological control of Daniela Stubbe, Nicolas Dandois, Leigh hawkweeds with insects. Proceedings Anne Walton, Anna Hassler and Susan of 6th Australasian Grassland Inverte- Murphy for technical assistance in Swit- brate Ecology Conference, 15–19 Febru- zerland. This work was funded by the ary 1993, AgResearch, Ruakura Agri- New Zealand Foundation for Research, cultural Centre, Hamilton, New Zea- Science and Technology under contract land, ed. R.A. Prestidge, pp. 426-32.