Effect of Racemic Disparlure Released from Grids of Plastic Ropes on Mating Success of Gypsy Moth (Lepidoptera: Lymantriidae) as Influenced by Dose and by Population Density

Abstract

Studies were done in Cecil County, Md., during summer 1981 in which racemic disparlure was used to disrupt mating of the gypsy moth, Lymantria dispar (L). The disruptant was applied in ropes of laminated plastic tape manually placed in a grid in replicated I-ha forest plots at the rates of 0, 25, or 250 g (AI)/ha. Significant decreases in male trap catch and in mating success occurred with increasing dose for both released and natural populations of female moths. Both trap catch suppression and female mating disruption were density dependent; greater suppression occurred in lower density gypsy moth populations than in higher density populations for a given dose of disruptant. The presence or absence of traps baited with pheromone did not significantly affect female matching success. The 250 g (AI)/ha dose of disruptant suppressed populations of 40 immatures per burlap band. Because of the current cost of the disruptant, population suppression by mating disruption appears to be practical only when relatively low doses of disruptant are used against low density populations of gypsy moths.