Dose-response relationships of neonicotinyl insecticides to Blissus occiduus and B. leucopterus hirtus

Neonicotinoid insecticides are generally highly efficacious against many turf pests, particularly phloem-feeding insects. Imidacloprid and thiamethoxam, however, have shown only moderate to poor control of Blissus occiduus. In contrast, acceptable but somewhat inconsistent levels of control have been reported for B. leucopterus hirtus. This study documented the differential mortality of selected neonicotinyl insecticides against B. occiduus in field trials. Two field studies evaluated levels of B. occiduus mortality with clothianidin, imidacloprid, and thiamethoxam. In these studies, clothianidin provided >85% control of both first and second generation chinch bugs. Imidacloprid and thiamethoxam, however, provided <85% control. To document the dose-response relationships of these insecticides to B. occiduus and B. l. hirtus, we conducted systemic and contact bioassays. In the systemic bioassays, third and fourth instar B. occiduus and B. l. hirtus were exposed to technical grade imidacloprid, clothianidin, and thiamethoxam to document insecticide activity at lethal and sublethal concentrations. A companion study evaluated the contact activity of these insecticides. Third and fourth instar B. occiduus and B. l. hirtus were placed in vials treated with technical grade imidacloprid, clothianidin, thiamethoxam, and bifenthrin, a synthetic pyrethroid commercial standard. Results of these studies will be presented at the 2008 Entomological Society of America meeting. These studies will provide a better understanding of insect/plant/insecticide interactions which will ultimately improve chinch bug management techniques.