Laboratory and Field Evaluation of Piperonyl Butoxide as a Pyrethroid Synergist Against the Colorado Potato Beetle (Coleoptera: Chrysomelidae)

Abstract

Laboratory and field studies showed that piperonyl butoxide (PB) synergizes both permethrin and fenvalerate against the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say. In laboratory studies, synergist ratios (SR) for CPB adults varied from 1.39- to 4.57-fold depending on the insecticide and the insecticide: PB ratio. Synergism increased as the insecticide: PB ratio increased, but fenvalerate was more toxic to CPB adults and was synergized to slightly higher levels than was permethrin. CPB larvae were 3.39-fold more susceptible on the average than adults (range, 2.3–5.2) and fenvalerate was, again, more toxic than permethrin. Both insecticides were synergized by PB, but lower SR values suggest a less developed mixed-function oxidase detoxication system in CPB larvae. In field trials on eggplant, Solanum melongena L., PB was tank-mixed at 1:0, 1:1, 1:2, and 1:4 ratios (insecticide: PB) with pyrethroid dosages of 0.056 kg (AI)/ha in 1981 and 0.056, 0.112, and 0.224 kg (AI)/ha in 1982. During both years the pyrethroid: PB combinations provided significantly greater CPB control than did comparable dosages of pyrethroids alone.