Plant Protection Quarterly Vol.21(1) 2006 43 inadequately treated, but it is also possible Arrival of leaf-feeding willow sawfl y Nematus that adults were blown across the Tasman Sea in the easterly wind systems associated oligospilus Förster in Australia – pest or benefi cial? with major weather patterns in late sum- mer. As new single populations have been E. BruzzeseA,C and R. McFadyenB,C found as far away from Canberra as the A Primary Industries Research Victoria, Department of Primary Industries, Adelaide Hills and Melbourne, the wind PO Box 48, Frankston, Victoria 3199, Australia. dispersal theory is highly likely. Because of the current rapid pattern of dispersal in B Block B, 80 Meiers Road, Indooroopilly, Queensland 4068, Australia. C Australia, it is likely to spread to all willow CRC Australian Weed Management. areas in the next 2–3 years, including Tas- mania and Western Australia.

Summary Origin and spread Biology, impact and host range Willows are trees and shrubs native to Although fi rst recorded in Canberra, ACT, Charles et al. (1999) outlines the spread, the northern hemisphere and considered in March 2004, the identifi cation of N. oli- biology and host range of N. oligospilus in as either invasive weeds, or desirable for gospilus was only confi rmed in February New Zealand where it has been recorded amenity purposes in temperate Australia. 2005 (Rees et al. 2005). The sawfl y is na- on crack willow (S. fragilis), twisted, cork- The leaf-feeding willow sawfl y Nematus tive to the northern hemisphere, where it screw, or tortured willow (S. matsudana cv. oligospilus was recently identifi ed as a is found from Ireland through continental ‘Tortuosa’), Peking or matsudana willow new incursion to Australia and its po- Europe to the Himalayas, and also occurs (S. matsudana), weeping willow (S. baby- tential pest or benefi cial attributes are in North America from Alaska to Mexico. lonica), pencil willow (S. humboldtiana cv. discussed. It was fi rst recorded in the southern hemi- Chilensis), golden willow (S. alba var. vitel- Keywords: Salix, willows, willow sphere in Argentina in 1980, in southern lina) and hybrid willow cultivars (S. mat- sawfl y, Nematus oligospilus. Africa in 1993/94, in New Zealand in 1997 sudana × S. alba cvs. ‘Tangoio’, ‘Moutere’, (Charles et al. 1999) and 2004 in Australia. ‘Aokautere’). In laboratory trials in New Introduction In Australia, a sawfl y infestation on Zealand, Charles et al. (1998) found that The leaf-feeding willow sawfl y Nematus oli- weeping willow (Salix babylonica) was fi rst the sawfl y would lay eggs in the leaves gospilus Förster (Hymenoptera: Tenthredi- noticed by one of us (EB) in Telopea Park, of 23 tree willow genotypes indicating nidae) is a new introduction to Australia Manuka, ACT on 3 March 2004, and larval that tree willows (Salix subgenus Salix) (Rees et al. 2005) and is spreading rapidly. specimens were collected for rearing and are susceptible to defoliation. However Willows (Salix spp., Salicaceae) are dio- identifi cation. The next day, extensive de- shrub willows (Salix subgenus Caprisalix) ecious, deciduous trees and shrubs that foliation was noticed on weeping and crack were not selected. Based on New Zealand are principally native to the northern willow growing along the Molonglo River experience, it is highly likely that the saw- hemisphere. Many willow species were at Duntroon, ACT, and CSIRO Entomol- fl y will impact on the wide range of tree deliberately introduced for basket-mak- ogy and willow experts were informed. willows naturalized in Australia, but the ing, cricket bat production, stream stabi- Subsequently, defoliation was recorded as shrub willows may not be attacked. lization, ornament and shelter and con- far as 150 km south of Canberra in 2004 (K. tinue to be used for a range of purposes, Cremer personal communication). Preliminary observations with over 45 taxa available in the nurs- Spread of this insect in Australia has In Australia, the sawfl y has, to date, been ery trade (ARMCANZ et al. 2000). Of the been rapid. In January 2005 defoliation of recorded on crack willow (S. fragilis), naturalized willows in Australia, several willows was reported in the Queanbeyan twisted, corkscrew, or tortured willow are highly invasive because of their sexual Age newspaper along the Queanbeyan (S. matsudana cv. ‘Tortuosa’) and weeping and vegetative reproductive ability. The and Molonglo Rivers and around Lake willow (S. babylonica). A total of 52 larvae problems caused by naturalized willows Burley Griffi n in Canberra (Anon. 2005a). at different stages of development were in Australia have been recognized by the The Southern Rivers Catchment Manage- collected from S. babylonica in Canberra fact that all Salix taxa, excluding S. baby- ment Authority reported defoliated wil- on 3rd March 2004 and transported to the lonica, S. × calodendron and S. × reichardtii, lows at Braidwood, 110 km east of Can- DPI Quarantine Facility in Frankston, Vic- have been listed as Weeds of National Sig- berra (Exon 2005). These rates of spread toria where they were fed on S. babylonica nifi cance (ARMCANZ et al. 2000). approximate the New Zealand experience sprigs until they spun cocoons. Fresh wil- Based on overseas experience, the leaf- where dispersal of about 300 km per year low sprigs were presented every second feeding willow sawfl y is likely to severely has been recorded (Charles and Allan day and cocoons collected in small plastic impact on a range of tree willow species in 2000). In February 2005 an infestation was containers and held at 20°C until adult Australia. It is therefore likely to be viewed found in the Adelaide Hills in South Aus- emergence. A total of 47 female adults as a pest or benefi cial insect depending tralia (J. Virtue personal communication and no males emerged 5–7 days after co- on the species of willows it defoliates in 2005) while in April 2005 an infestation coons were spun. Adults were placed in Australia. In April 2005, the Offi ce of the was reported and confi rmed in Victoria wide plastic containers with fresh willow Chief Plant Protection Offi cer posted the at East Keilor, a north-western suburb of branches and died 4–6 days after emer- following information (Anon. 2005b) ‘the Melbourne. These are approximately 1200 gence. Leaves were checked for eggs but Consultative Committee on Emergency km and 650 km respectively from the main none were observed. Deceased adults Plant Pests has considered that given the Canberra infestation. were pinned for later identifi cation. presence of willow sawfl y in the Austral- It is not known how the sawfly has These observations confi rm New Zea- ian Capital Territory (Canberra), NSW and spread around the southern hemisphere in land observations that the species is the- SA, and the large number of host plants the last 25 years, nor how it reached Aus- lytokous and only female adults emerge in southern Australia, the pest is too tralia, but there is a possibility that it ar- (Charles et al. 1998). This seems to be true widespread to be eradicated’. This note rived from New Zealand where it has been wherever the species has invaded in the discusses the potential pest and benefi cial widespread for at least eight years (Charles southern hemisphere while in the north- attributes of N. oligospilus. et al. 1999). It may have arrived as cocoons ern hemisphere, adults of both sexes are on plant material or packaging that were found (Urban and Eardley 1995). 44 Plant Protection Quarterly Vol.21(1) 2006 Observations at the Victorian infesta- viduatus (Zetterstedt)), recorded only on Plan 1 July 2004 to 30 June 2014 to in- tion confi rm New Zealand observations the south coast of New South Wales. There corporate sawfl y remediation works for that pupation takes place in cocoons on may also be interactions with the range of the Heretaunga Plains Flood Control the tree, in litter and building structures foliar fungal pathogens, particularly rust Scheme. Hawkes Bay Regional Coun- surrounding the tree and in the soil. Nu- fungi already widespread on willows in cil. http://www.hbrc.govt.nz/Printer- merous cocoons were present on 12 April Australia (Sagliocco and Bruzzese 2002). Friendly.aspx?tabid=299 as well as fully fed larvae descending the There are indications from New Zea- ARMCANZ, ANZECC and Ministers, F. trunk to look for pupation sites. Cocoons land that repeated defoliation by the leaf- (2000). Weeds of National Signifi cance, contained mature larvae when dissected. feeding willow sawfl y over a period of Willows (Salix taxa excluding S. baby- years has had a devastating impact on wil- lonica, S. × calodendron and S. reichardtii) Pest or benefi cial? lows planted to protect riverbanks and hill Strategic Plan. Launceston, Agriculture The current status of willows in Australia country from erosion (Olsen 2005). There, and Resource Management Council of determines whether this insect will be con- willow suppression has been so severe Australia and New Zealand, Austral- sidered as a pest or a benefi cial. that the Hawkes Bay Regional Council has ian and New Zealand Environment All Salix spp except three taxa are listed estimated a 25–90% loss of effectiveness of and Conservation Council and Forestry as Weeds of National Signifi cance because willows for stream bank stabilization and Ministers, National Weeds Strategy Ex- they cause water degradation and loss of is planning stream rehabilitation works ecutive Committee. biodiversity in riparian and aquatic ecosys- (Anon. 2005c). Charles, J.G. and Allan, D.J. (2000). Devel- tems, and a National Strategic Plan for the If the New Zealand experience is re- opment of the willow sawfl y, Nematus management of willows has been published peated here, we can expect severe yearly oligospilus, at different temperatures, (ARMCANZ et al. 2000). It is estimated that defoliation of most species of tree willows and an estimation of voltinism through- willow management along waterways by each summer that may ultimately kill trees. out New Zealand. New Zealand Journal mechanical and chemical methods costs Defoliation in mid-summer leads to loss of of Zoology 27, 197-200. $10 million annually. The National Strate- shade with the potential of increased water Charles, J.G., Allan, D.J., Froud, K.J. and gic Plan for Willows has identifi ed biologi- temperatures, however, the additional sun- Fung, L.E. (1999). A guide to willow cal control as a desirable management op- light may assist the establishment of com- sawfly (Nematus oligospilus) in New tion that can be used to suppress willows in peting native vegetation. The arrival of the Zealand http://www.hortnet.co.nz/ dense, lower priority infestations. sawfl y provides the opportunity to monitor publications/guides/willow_sawfl y/ The leaf-feeding willow sawfl y is there- its impact on willows in riparian situations wsawfl y.htm fore likely to be considered as a benefi cial and the resulting changes in the aquatic Charles, J.G., Allan, D.J. and Fung, L.E. by natural resources management authori- and riparian environment. It would be de- (1998). Susceptibility of willow to ovipo- ties responsible for removing willows as sirable to establish a network of long-term sition by the willow sawfl y, Nematus oli- part of stream and wetland rehabilitation. sites to monitor the impact of the sawfl y on gospilus. Proceedings 51st New Zealand The benefi cial aspects of the sawfl y on weedy and non-weedy willow taxa grow- Plant Protection Conference, pp. 230-4. weedy willows will depend on the levels ing under different climatic conditions. Exon, F. (2005). Local willow stripped by of defoliation caused to the different inva- Where non-invasive tree willows are sawfl y. Media Release. Southern Rivers sive willow taxa, and the climatic require- valued as ornamental, amenity or herit- Catchment Management Authority. ments of the sawfly. Potential climatic age trees, it will be necessary to use regu- Naumann, I.D., Williams, M.A. and range predictions would require accurate lar insecticide treatments to protect the Schmidt, S. (2002). Synopsis of the Ten- distribution information from a range of trees. Insecticides are currently registered thredinidae (Hymenoptera) in Austral- areas where the thelytokous biotype has for control of leaf feeding sawfl ies in Eu- ia, including two newly recorded, intro- invaded the southern hemisphere, coupled calyptus plantations and these should be duced sawfl y species associated with with laboratory experiments to determine trialled prior to registration for control of willows (Salix spp.). Australian Journal temperature thresholds. The widespread N. oligospilus. of Entomology 41, 1-6. distribution in New Zealand suggests that Olsen, A. (2005). Sustainable Farming all of temperate southern Australia includ- Acknowledgements Fund project summary. Providing man- ing Tasmania would be suitable. We thank Aline Bruzzese and Jean-Louis agement options for the control of wil- It is diffi cult to predict whether native Sagliocco for assistance in the rearing of low sawfl y to protect unstable pastoral parasites and predators will attack this sawfl y adults and their preparation for hill country (and tree fodder) and river species. There are very few native Austral- identification. Dr. Mali Malipatil con- berms and erosion and shelter belts ian species in the Tenthridinidae sawfl y fi rmed the identifi cation of 2003 material from defoliation. http://www.maf. family (Naumann et al. 2002) so there is from Canberra and 2005 material from govt.nz/sff/about-projects/pastoral- probably only a small pool of family-spe- East Keilor. Dr. Mali Malipatil, Dr. John farming/02050sawfl y.htm cifi c parasites available but some general- La Salle and Mr. Bill Washington and two Rees, D., Stokes, K. and La Salle, J. (2005). ist parasites and predators may be present. anonymous referees are thanked for com- Willow sawfl y Nematus oligophilus [sic] Signifi cant parasitism and predation may ments on the manuscript. (Hymenoptera: Tenthredinidae) now es- limit the impact of the sawfl y. It would be tablished in Australia. Myrmecia 41, 4. useful to start gathering information on References Sagliocco, J.-L. and Bruzzese, E. (2002). In- parasitism and predation of the different Anon. (2005a). ‘Strip the willows’. Quean- vasive willows in Australia: could they life stages (egg, larvae and pupae) in dif- beyan Age (18/1/05), p.1 be targets for biological control? Pro- ferent regions of Australia. Anon. (2005b). Commonwealth of Aus- ceedings of the13th Australian Weeds Interactions with two other species of tralia, Offi ce of the Chief Plant Protec- Conference, eds H. Spafford Jacob, J. willow sawfl y already present in Australia tion Offi cer. Willow sawfl y incident. Dodd, and J.H. Moore, pp. 415-17 (Plant (Naumann et al. 2002) are likely as all three http://www.affa.gov.au/content/out- Protection Society of WA, Perth). willow sawfl y species continue to spread put.cfm?ObjectID=0E21BEB4-527B- Urban, A.J. and Eardley, C.D. (1995). A re- in Australia. The other two species are 4B50-8FC5A33287FB718A cently introduced sawfl y, Nematus oligos- the willow gall sawfl y (Pontania proxima Anon. (2005c). Statement of proposal for a pilus Förster (Hymenoptera: Tenthredi- Lepeletier), widespread in Tasmania, and change to Hawke’s Bay Regional Coun- nidae), that defoliates willows in south- the willow bud sawfl y, (Amauronematus cil’s Long Term Council Community ern Africa. African Entomology 3, 23-7.