Large field trial with microencapsulated sex pheromone to prevent mating of the gypsy moth.

Abstract

Just before the 1973 mating season of Porthetria dispar (L.), a microencapsulated formulation of disparlure, the synthetic sex pheromone of the insect, was applied at the rate of 5 g disparlure/ha to a 60-km2 forested area in Massachusetts that was naturally infested with the gypsy moth. Effect of this treatment on mating of the moth was determined by monitoring one hundred O.1-ha plots in both the treated area and in a similar nearby untreated (control) area. In traps baited with 10 μg disparlure, 2193 males were caught in the untreated area compared with 63 in the treated area; in female-baited traps, 1136 males were taken in the control compared with only one in the treated area. This reduction in trap captures indicates that the odor-guidance system that normally leads males to females for mating was disrupted by the treatment. Untethered virgin females also were placed on tree trunks to determine whether mating would be inhibited; mating in the treated area (relative to untreated area) was severely suppressed for the 1st 2-½ wk when the treatment was fresh; mating then increased as the treatment grew older but the treatment still exerted substantial disruption of mating 5 wk after application. Suppression of reproduction due to the treatment also was evident from egg-mass counts made before and after the test. The number of egg masses in the treated area did not rise significantly (+36 and +60%), whereas the rise in egg-masses in the untreated area (+193 and +254%) was highly significant. In addition, 15% of the postseason egg masses in the treated area were infertile compared with only 2% in the control area. A study of effect of plot location on the parameters of this study did not reveal any evidence of a substantial influx of males into the treated area. Prospects for using the pheromone to manage and eliminate populations are discussed.