Resistance of Colorado potato beetle (Coleoptera: Chrysomelidae) to neonicotinoids, pyrethroids and nereistoxins in Serbia

iColorado potato beetle (CPB, Leptinotarsa decemlineata Say) resistance is one of the limiting factors in potato production in some regions of Serbia. Imidacloprid is first introduced neonicotinoid insecticide in use for effective CPB control. Introduction of such insecticides with novel mode of action and physicochemical properties, demands investigations on resistance risks and management tactics. Primary candidates for cross resistance are insecticides acting on same target sites (such as bensultap, with CPB resistance reported), although other cross resistance patterns between apparently unrelated insecticides are not uncommon. Results of the investigations presented in this paper refers to the resistance of CPB adults to 3 insecticides - imidacloprid, bensultap and cypermethrin, most commonly used by farmers in recent years. First generation adults from nine field populations in first and four representative populations in second year of investigation were tested by topical application. Resistance ratios for bensultap ranged from 1.0 to 645.3 (LD50 from 0.04 – 25.81 μg/insect). Cypermethrin resistance ratios ranged from 1.0 to 60.0 (LD50 from 0.02 – 2.05 μg/insect). Imidacloprid resistance ratio was from 1.0 to 82.9 (LD50 from 0.0039 – 0.0323 ng/insect). Based on our results there was no correlation between resistance levels for bensultap and imidacloprid. Although LD50 values for imidacloprid were very low, significant resistance ratios obtained in these investigations, together with threads of cross-resistance and importance of conserving field efficacy of neonicotinoids, strongly recommands systematic resistance monitoring as important resistance management tool