Laboratory and field evaluation of spinosad against the gypsy moth, Lymantria dispar

Abstract

The toxicity of the naturally derived insecticide spinosad was tested against the gypsy moth, Lymantria dispar. Bioassays using red oak leaf disks, treated with spinosad in a Potter spray tower, yielded an LC50 value of 0.0015 µg AI cm−2 (3-day exposure; 13-day evaluation; 2nd instar larvae). Applied to foliage to run-off in the laboratory (potted red oak seedlings) and the field (4 m-tall birch trees), spinosad effectively controlled 2nd instar larvae at concentrations ranging from 3 to 50 mg litre−1. Toxicity in the laboratory, and efficacy and persistence in the field, were comparable to those achieved with the insecticide permethrin. Laboratory studies supported field observations that control was achieved in part by knockdown due to paralysis. In addition, laboratory results demonstrated that crawling contact activity may play an important role in field efficacy; 50% of treated larvae were paralyzed 16 h after a 2-min crawling exposure to glass coated with a 4 mg litre−1 spinosad solution. © 2000 Society of Chemical Industry