DISPARLURE PERSISTENCE IN THE FOREST

Authors: Thorpe, Kevin; TCHESLAVAKAIA, KSENIA - VA TECH

Submitted to: Proceedings of the Spray Efficacy Research Group (SERG)
Publication Type: Proceedings
Publication Acceptance Date: 2/20/2006
Publication Date: 4/10/2006
Citation: Thorpe, K.W., Tcheslavakaia, K.S. 2006. Disparlure persistence in the forest. Proceedings of the Spray Efficacy Research Group (SERG). International & USDA Forest Service Worskshop, Banff, ALberta, Canada. February 13-16, 2006. pg. 27-33.

Interpretive Summary: The gypsy moth is the most destructive defoliator of hardwood forests in the northeastern United States. Mating disruption is the primary tactic used in the national Slow-the-Spread of the Gypsy Moth program (STS) to reduce the rate of expansion of gypsy moth populations into new areas. Mating disruption has been shown to be a highly effective and environment-friendly method to control gypsy moth populations. In 2004 and 2005, experimental plots that had been treated with a gypsy moth mating disruption formulation the previous year were monitored to determine if the effects of the treatment persisted into subsequent years. Capture of male moths in traps was reduced from 38 – 56%, and female mating was reduced from 63 – 80%. The continued suppression of trap catch could be a problem in STS, because traps are used to determine if treatments were successful and to determine if additional treatments are needed. The persistent effects of the treatments into successive years may interfere with the effectiveness of the traps as a monitoring tool. On the other hand, the continued suppression of mating is a potential benefit of the persistent effects of the treatment. This information will help gypsy moth managers interpret the results of trap data in STS and will assist researchers in developing improved methods for monitoring gypsy moth populations.

Technical Abstract: The persistence of the gypsy moth, Lymantria dispar (L.), sex pheromone, disparlure, in forested plots treated one and two years previously with a commercial plastic laminate flake mating disruption formulation was investigated. Recapture of male moths released into plots treated the prior year with Disrupt II flakes at an application rate of 15 g a.i./acre was reduced by 38% compared to controls in 2004 and by 56% in 2005. Female mating success in these plots was reduced by 63% compared to controls in 2004 and by 80% in 2005. Trap catch was reduced in plots treated the prior year at 6 g a.i./acre by 39% compared to controls and female mating success was reduced by 92%. Trap catch and mating success were reduced by 39 and 36% compared to controls in plots treated 2 years previously at 15 g a.i./acre. It is not known if the persistent effects of disparlure applications results from continued release of pheromone from flakes or from environmental contamination. The persistence of the effects of disparlure is of concern to gypsy moth managers because it impairs their ability to detect moth populations in previously-treated areas. Conversely, the continued reduction in mating success may increase the effectiveness of mating disruption treatments by providing multi-year population suppression.