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

The toxicity of the naturally derived insecticide spinosad was tested again st the gypsy moth, Lymantria dispar. Bioassays using red oak leaf disks, tr eated with spinosad in a Potter spray tower, yielded an LC50 value of 0.001 5 mu g AI cm(-2) (3-day exposure; 13-day evaluation; 2nd instar larvae). Ap plied to foliage to run-off in the laboratory (potted red oak seedlings) an d the field (4 m-tall birch trees), spinosad effectively controlled 2nd ins tar larvae at concentrations ranging from 3 to 50mg litre(-1). Toxicity in the laboratory, and efficacy and persistence in the field, were comparable to those achieved with the insecticide permethrin. Laboratory studies suppo rted field observations that control was achieved in part by knockdown due to paralysis. In addition, laboratory results demonstrated that crawling co ntact activity may play an important role in field efficacy; 50% of treated larvae were paralyzed 16h after a 2-min crawling exposure to glass coated with a 4mg litre(-1) spinosad solution. (C) 2000 Society of Chemical Indust ry.