Residual Activity of Selected Insecticides Against the Adult Mexican Bean Beetle (Coleoptera: Coccinellidae) on Soybeans1

Abstract

Field cage studies were conducted for 2 yr to determine the residual toxicities of permethrin, cypermethrin, acephate, methomyl and several carbaryl formulations against adult E. varivestis Mulsant on soybeans. Tests showed that the residual, wash-off-resistant carbaryl formulations Sevin XLR and UCSF-27 provided control of adult beetles from 14-21 days posttreatment. In order of decreasing duration of effectiveness, those 2 formulations were followed by acephate, permethrin and cypermethrin, which were active from 7 to 14 days: carbaryl (Sevin 80S), active for 7 days and methomyl, which provided < 7 days of control. Although not as active as the residual formulations of carbaryl in causing mortality, permethrin and cypermethrin apparently provided further protection to the soybeans by repelling the adults from the plants past their periods of lethality. This repellency was characterized by low levels of defoliation and by adult beetles avoiding the treated leaves by clinging to the cage or stems.