1. Host Preferences of the Colorado Potato Beetle Leptinotarsa Decemlineata Erin M. Hitchner 1, Thomas 2 P. Kuhar, Joseph C. Dickens 3 and Rod Youngman 1 1 Department of Entomology, Virginia Tech, VA 2 Department of Entomology, Virginia Tech, Eastern Shore AREC, VA 3 USDA-ARS BARC, Beltsville, MD Introduction The Colorado potato beetle (CPB) has been identified as feeding on a variety of solanaceous and non-solanaceous crops (Hsiao & Fraenkel 1968). Potato, Solanum tuberosum, is the preferred host for CPB (Hsiao & Fraenkel 1968); however, other solanceous crops such as eggplant, tomato, and pepper, also serve as suitable hosts. It has been noted that there may be different host plant adaptations among geographic populations of the beetle (Hsiao 1978). Based on field observations, CPB appear to strongly prefer eggplant over other solanaceous plants. It is feasible that CPB preference for eggplant could perhaps be used in a trap crop pest management strategy. The objectives of our study were to determine the relative host plant preferences of CPB among eggplant, tomato and pepper in the field, and to evaluate the potential of an eggplant trap crop strategy. Materials & Methods Field studies were conducted in the summer of 2005 at the Eastern Shore Agricultural Research & Extension Center in Painter, VA. The multiple-crop choice study included eggplant, tomato, and pepper as potential host plants. The three crops were arranged in a single row and were replicated four times. Each row consisted of a 6 m section of eggplant, 6 m section of tomato and a 6 m section of pepper for a total row length of 18 m. The three treatments were as follows: 1) all plants were treated prior to transplanting with a drench of imidaclopird (138 g ai/ha); 2) eggplants only were treated with an imidacloprid drench (138 g ai/ha) prior to transplanting; 3) all plants were untreated. CPB infestations (including dead and alive adults, larvae, and egg masses) in each block were monitored approximately twice a week for one month. Insect counts were analyzed using standard ANOVA. Tukey’s HSD was used to separate treatment means at the P < 0.05 level of significance. Fig 1: Multi-crop choice study with eggplant, tomato, and pepper. Results The untreated eggplants had considerably more feeding damage from the CPB than eggplants treated with imidacloprid (Fig 2). Significantly more CPB adults (f=18.93; P < 0.00001), larvae (f = 13.01; P < 0.00001) and egg masses (f = 12.24, P < 0.00001) were found on untreated eggplants than on untreated tomatoes or untreated peppers (Fig. 3). In imidacloprid treated plots, more dead CPB adults were found on eggplants than on tomatoes or peppers (Fig. 4) (f = 8.56, P < 0.0004). Compared to all pepper plants, untreated tomato plants (treatments 2 and 3) had significantly more CPB adults (f = 4. P < 0.0019) and egg masses (f = 3.92, P < 0.0022) (Fig. 5). Treatment 2, in which eggplants only were treated with imidacloprid, did not show a significant reduction of CPB adults, larvae and egg masses on tomato plants compared to Treatment 3 in which all plants were untreated (Fig. 5). Fig. 3: Mean number of CPB adults, larvae and egg masses per 5 plants over time in untreated eggplant, pepper and tomato; Painter, VA, 2005. Fig. 4: Mean number of CPB dead adults per 5 plants over time in imidacloprid treated eggplant, pepper and tomato; Painter, VA, 2005 Fig. 5: Mean number of CPB adults, larvae and egg masses per 5 plants over time in pepper and tomatoes with various treatments; Painter, VA, 2005. Untreated eggplant Fig. 2: Untreated and Imidacloprid treated eggplant June 6, 2005 Abstract The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is a major pest of solanaceous crops in the United States. Although the beetle feeds on a variety of solanaceous plants, eggplant, Solanum melongena, appears to be a highly-preferred host crop based on past field observations. We conducted field trials in Virginia in 2005 to evaluate the host preference of CPB for eggplant, and its potential use in a trap crop pest management strategy with intercroppings of eggplant, tomato and pepper. Untreated eggplant had significantly more CPB adults, eggs, and larvae than tomato or pepper. Eggplant treated with the systemic insecticide, imidacloprid, had significantly more dead beetles than treated tomato or pepper. However, in plots in which eggplant only was treated with imidacloprid, CPB numbers on the untreated intercropped tomato or pepper were not reduced. References Cited Blom, P.E., Fleischer, S.J., Smilowitz, Z. 2002. Spatial and temporal dynamics of Colorado potato beetle (Coleoptera: Chrysomelidae) in fields with perimeter and spatially targeted insecticides. Environmental Entomology 31: 149-159. Hsiao, T. H. 1978. Host plant adaptations among geographic populations of the Colorado potato beetle. Entomologia Experimentalis et Applicata 24: 437-447. Hsiao, T. and G. Fraenkel. 1968. Selection and specificity of the Colorado potato beetle for solanaceous and nonsolanaceous plants. Annals of the Entomological Society of America 61: 493-503. * * * * Discussion Results of our study showed that the Colorado potato beetle prefers eggplant as a host crop over tomato or pepper. Pepper is least preferred, and does not even appear to be a suitable host for CPB egg-laying or larval development. Although this experimental design did not effectively reduce CPB numbers in tomatoes or peppers by treating eggplant only, alternative experimental designs may prove successful. For instance, surrounding the perimeter of the tomato crop with treated eggplant. Perimeter treatments of potatoes with imidacloprid have been shown to successfully control CPB populations (Blom et al. 2002) Imidacloprid treated eggplant ** Courtesy:http:// www.thetreefarm.org/veg_pages/eggplant.html Courtesy:http:// www.mgonlinestore. com/WFETomato / Courtesy:http:// finsonfarm.com/daily/08252001- green-pepper.html