Residual Efficacy of Cyfluthrin Applied Alone or in Combination with Piperonyl Butoxide or Piperonyl Butoxide + Chlorpyrifos-methyl as Protectants of Stored Corn2

Abstract

Pioneer variety ‘3320’ seed corn, treated with 0.5, 1.0, 1.5, or 2.0 ppm cyfluthrin, each rate of cyfluthrin + 8.0 ppm piperonyl butoxide, or each rate of cyfluthrin + 8.0 ppm piperonyl butoxide + 6.0 ppm chlorpyrifosmethyl, was stored for 10 months at ambient conditions in south Georgia. Every 2 months the corn was sampled and bioassayed with maize weevil, Sitophilus zeamais (Motschulsky), and red flour beetle, Tribolium castaneum (Herbst). Maize weevil survival on corn treated with 0.5, 1.0, and 1.5 ppm cyfluthrin ranged from 39.5 to 76.0%, 4.0 to 29.5%, and 1.0 to 11.5%, respectively. Weevils did not survive exposure on corn treated with 2.0 ppm cyfluthrin, each rate of cyfluthrin + piperonyl butoxide, or each rate of cyfluthrin + piperonyl butoxide + chlorpyrifos-methyl. F1 progeny and dockage (ground corn flour and insect frass) in incubated bioassays were correlated with initial survival. Red flour beetle survival on corn treated with cyfluthrin alone or cyfluthrin + piperonyl butoxide was variable throughout the test, although survival at any bioassay usually decreased as the rate of cyfluthrin increased. However, no F1 adults or dockage was detected in any incubated bioassay from the 12 chemical treatments.