Gypsy moth mating disruption: Dosage effects

Small (1-hectare) plots in a dense gypsy moth (Lymantria dispar) infestation were treated with 5, 50, or 500 g racemic disparlure, and effects on male trap catch and mating behavior were studied. Capture of males in traps baited with 1, 10, 100, or 1000 μg (+)-disparlure declined as disruptant dosages increased. Traps with high levels of attractant caught moths when capture in those with lower baitings was dramatically reduced. While all disruptant dosages reduced trap catch, it was reducd at least 95% at all attractant levels at the 500-g disruptant application rate. Visual estimates indicated that male moth density was similar in treated and control plots; female mating success was reduced 6.5, 34.5, and 84% in plots with 5, 50, and 500 g/ hectare disruptant, respectively. The duration of precopulatory and copulatory periods was similar for all females that were observed mating, regardless of disruptant treatment. It is proposed that reduced trap catch and female mating success are due to effects of atmospheric synthetic disparlure (disruptant) camouflaging natural attractant point sources.