Establishment of Parasitoids of the Lily Leaf Beetle (Lilioceris lilii) in New England Lisa A. Tewksbury, Richard A. C

1. Establishment of Parasitoids of the Lily Leaf Beetle (Lilioceris lilii) in New England Lisa A. Tewksbury, Richard A. Casagrande University of Rhode Island, Dept. of Plant Sciences Tetrastichus setifer Thomson Diaparsis jucunda (Holmgren) Lilioceris lilii (Scopoli) Tetrastichus setifer (Fig. 6) will attack all instars of L. lilii larvae. Parasitized larvae continue to feed and prepare a cocoon for pupation in the soil.After the cocoon is made, the L. lilii larva becomes a mummy containing an average of 10 parasitoid larvae (Fig. 7).Tetrastichus setifer larvae emerge from this mummified larva and pupate within the cocoon of the host where they spend the winter in an obligatory diapause (Fig. 8). Adult parasitoids emerge the following spring and attack lily leaf beetle larvae.European field research indicates that T. setifer is the most widespread parasitoid of L. lilii in Europe, occurring in all regions investigated, from Bulgaria to UK and Northern Germany to Italy (Kenis et al. 2002) and occurs in areas where no other parasitoids are found. Based upon the European distribution, we could expect T. setifer to survive in all of the present US range of L. lilii except possibly in northern Vermont and Maine.Tetrastichus setifer host range tests indicated specificity to subfamily (Criocerinae). Diaparsis jucunda has a life cycle similar to L. errabundus. Diaparsis jucunda attacks all larval stages and is the dominant parasitoid of L. lilii in central and southern Europe with total parasitism in the last instar averaging about 60% in lily fields, 74% in gardens, and 90% on the wild Lilium martagon (Kenis et al. 2002). Research on host specificity of L. errabundus, published by Gold (2003) shows this species to be host-specific to L. lilii. Fig. 1: Lily leaf beetle adult Fig. 2: Lily leaf beetle eggs The lily leaf beetle, Lilioceris lilii (Coleoptera: Chrysomelidae) (Figs. 1-3), is native to Eurasia. It was first found in North America near Montreal in 1945, and reported in Boston, MA in 1992. It is a serious pest of native and cultivated lilies (Liliaceae) and is currently distributed throughout most of New England, and into New York (Fig. 4). Fig. 9: Diaparsis jucunda Table 3: Field releases of Diaparis jucunda adults Results/Discussion Tetrastichus setifer is successfully established in Massachusetts, Rhode Island, New Hampshire, and Maine. In 2004 we noted a reduction in the number of lily leaf beetle larvae in the Wellesley, MA release site, compared to 2003. In Cumberland, Rhode Island, T. setifer had spread five miles from the release site by 2005 (Fig. 10), and by 2006 it was found seven miles away from the release site. We also confirmed that Lemophagus errabundus is established in Massachusetts and Rhode Island. It was released near the border of these two states. This parasitoid has been recovered approximately 2 miles from the initial release site. Diaparsis jucunda was released in Rhode Island, Maine, and New Hampshire, and at this time is not successfully established in any of the three states. Fig. 6: Tetrastichus setifer Fig. 7: T. setifer larvae in L. lilii mummy Fig.8: T. setifer larvae in L. lilii cocoon Fig. 3: Lily leaf beetle larva Fig. 4: Distribution of the lily leaf beetle (USDA APHIS PPQ NAPIS 2005) Introduction/Methods There were no reports of natural enemies of L. lilii in Europe until Gold et al. (2001) surveyed France and Switzerland and identified four larval parasitoids, Tetrastichus setifer Thomson (Hym: Eulophidae), Lemophagus pulcher Szepliggeti (Hym: Ichneumonidae), L. errabundus Gravenhorst, and Diaparsis jucunda (Holmgren) (Hym: Ichneumonidae). Lemophagus errabundus and the fly Meigenia mutabilis (Dip: Tachinidae) had been previously recorded from L. merdigera in France (Elliott and Morley, 1911). Haye (2002) assessed the parasitoid complex of L. lilii in Europe. We received approval from the USDA and State Departments of Agriculture to release Tetrastichus setifer, Lemophagus errabundus, and Diaparsis jucunda. Parasitized L. lilii larvae were collected in Europe by CABI Bioscience Switzerland Centre, and were sent to the URI Quarantine Lab for emergence. Release and control plots of Asiatic and Oriental lilies were established throughout New England (MA, RI, NH, and ME) (Fig. 5). All plots were monitored for lily leaf beetle adults, eggs, and larvae, and fourth instars were collected for dissection to detect parasitism. Each year we checked for successful parasitism of overwintered wasps before making additional releases in a field plot. Table 1: Field releases of Tetrastichus setifer adults Lemophagus errabundus Gravenhorst This solitary univoltine parasitoid oviposits in larvae of L. lilii, which continue to feed, and develop, until a cocoon is formed in the soil. The L. lilii larvae then die and L. errabundus cocoons overwinter inside L. lilii cocoons in the soil. Lemophagus errabundus is more prevalent in northern Germany, Holland and western France with parasitism rates reaching over 70% among late instars. In these areas temperatures are more moderated by the ocean. Great Britain and the Netherlands also have maritime climates and T. setifer and L. errabundus are the predominant parasitoids (Kenis et al. 2002). Based upon the European distributions, it appears that L. errabundus is more suited for Cape Cod and coastal Southern New England. Research on host specificity of L. errabundus, published by Gold (2003) shows this species to be host-specific to L. lilii. Fig. 10: Recovery of T. setifer from area surrounding release site in Cumberland, RI in 2005 References: Gold, M.S. 2003. Biological control of the lily leaf beetle, Lilioceris lilii in North America. PhD. Dissertation. University of Rhode Island, Kingston, RI. Elliott, E.A. and C. Morley. 1911. On the Hymenopterous Parasites of Coleoptera. First Supplement. Transactions of the Entomological Society of London, pp. 452-497. Haye, T. 2002. Oekologische Studien zum Parasitoidencomplex von Lilioceris lilii Scopoli (Coleoptera: Chrysomelidae) an ausgewahlten mitteleuropaischen Standorten. Diploma Thesis. University of Kiel, Germany. Gold, M.S., R.A. Casagrande, L.A Tewksbury, M. Kenis, and S.B. Livingston. 2001. European Parasitoids of the lily leaf beetle, Lilioceris lilii Scopoli (Coleoptera: Chrysomelidae). Canadian Entomologist. 133:671-674. Kenis, M., T. Haye, R.A. Casagrande, M.S. Gold and L.A. Tewksbury. 2002. Selection and importation of European parasitoids for the biological control of the lily leaf beetle in North America, and prospects for control in Europe. Proceedings of First International Symposium of Biological Control of Arthropods (ISBCA) Meeting. Honolulu, Hawaii. Adult parasitoids were released in June and July each year; T. setifer from 1999-2006 (Table 1), and L. errabundus and Diaparsis jucunda from 2003-2006 (Tables 2 &3). After recovering overwintering T. setifer and L. errabundus in Cumberland, RI we conducted an intensive sampling of L. lilii larvae from home gardens within a seven mile radius of the release site to determine the natural spread of both parasitoids. Table 2: Field Releases of L. errabundus adults Acknowledgements: We have received funding from the following organizations, the North American Lily Society, White Flower Farm, Van Bloem Nurseries, USDA APHIS, USDA-NE Region IPM Program, CABI Bioscience Switzerland Centre, New England Greenhouse Conference, and the NH Horticultural Endowment. Fig. 5: Field plot in Kingston, RI Fig. 9: Lemophagus errabundus