Activity of Clofentezine Against European Red Mite (Acari: Tetranychidae)

Abstract

The ovicidal and larvicidal activity of clofentezine against a population of European red mite (ERM), Panonychus ulmi (Koch), was evaluated in laboratory bioassays and compared with activity of hexythiazox. Clofentezine was more active against summer than winter eggs of ERM; LC50 values of eggs in an early developmental stage differed by 11 times (1.01 and 11.1 ppm, respectively). Eggs of either type were significantly less susceptible to clofentezine when treated the day before hatch than when treated at earlier developmental stages (P < 0.02). When exposed to leaves treated with 10-100 ppm clofentezine, mortality was high among larvae but negligible among nymphs and adults. The amount of clofentezine required to kill 50% of winter or summer eggs was half that of hexythiazox. Winter eggs surveyed from 31 commercial apple orchards in three regions of New York did not vary significantly (P = 0.11) in susceptibility to clofentezine at a concentration of 100 ppm, but eggs from Champlain Valley orchards were less susceptible than those from the Hudson Valley or Wayne County when tested at 10 ppm (P = 0.0003).