Monitoring gypsy moth pheromone flake canopy through-fall

Indiana Department of Natural Resources and USDA Forest Service applied pheromone flakes, disparlure, to a very low-level gypsy moth (Lymantria dispar) population in south-central Indiana in June 2008 to eradicate the infestation. One aerial application of Disrupt II, a disparlure-based mating disruptor, was applied over the forest canopy. The fall of the flakes through the forest canopy to the forest floor was monitored using 50.8 x 76.2 cm white foam core boards. Percent canopy cover and distance from the plane's flight lines had no effect on canopy through-fall. Only 0.73 flakes per m super(2) were recorded, compared to 22 flakes per m super(2) on average that would have been deposited on areas without tree canopy. These figures indicated that in this study 96.7% of the applied flakes were retained in the canopy and only 3.3% constituted canopy through-fall. There was only a minimal chance that pheromone flakes would land in streams or cave openings within the area studied.