Efficacy of Duplex and Vectobac against Psorophora columbiae and Anopheles quadrimaculatus larvae in Arkansas ricefields.

The discovery of. Bacillu,s thuringiensis var. israel.ensis erotype H-14 (B.t.i.) and its subsequent commercial development have greatly benefited integrated pest management (IPM) practices against mosquitoes. Various formulations, application methods and production procedures have resulted in efficient and environmentally safe products (Margalit and Dean 1985). Tests in Arkansas ricefields using B.t.l. have demonstrated excellent control against Psorophora columbia.e (Dyar and Knab) and Anopheles qua.drimacularius Say (Stark and Meisch 1983). This and other studies have provided data which augmented the commercial development of Vectobac@,4 a B.t.i. formulation. The insect growth regulator (IGR), methoprene, prevents adult emergence and has been shown to be effective against mosquito larvae (Mulla and Darwazeh 1975, Walker 1987). Methoprene has been used in combination with various mosquito pathogens. These combinations resulted in higher mortality to test insects than when methoprene or pathogens were applied separately (Finney et al. 1977, Spencer and Olson 1982, AIIen and Sweeney 1985). Recent interest in improving B.t.i. efficacy by addition of methoprene has surfaced. This paper reports on tests conducted in 1987 using Duplex@,u a compound containing methoprene (IGR) and, B.t.i., against Ps. colurnbiae and An. quadrimaculatus in Arkansas ricefields.