Optimization of pheromone dosage for gypsy moth mating disruption

Abstract

The effect of aerial applications of the pheromone disparlure at varying dosages on mating disruption in low-density gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), populations was determined in field plots in Virginia, USA during 2000 and 2002. Six dosages [0.15, 0.75, 3, 15, 37.5, and 75 g active ingredient (AI)/ha] of disparlure were tested during the 2-year study. A strongly positive dose-response relationship was observed between pheromone dosages and mating disruption, as measured by the reduction in male moth capture in pheromone-baited traps and mating successes of females. Dosages of pheromone ≥ 15 g AI/ha (15, 37.5, and 75 g AI/ha) reduced the mating success of females by >99% and significantly reduced male moth catches in pheromone-baited traps compared to untreated plots. Pheromone dosages <15 g AI/ha also reduced trap catch, but to a lesser extent than dosages ≥ 15 g AI/ha. Furthermore, the effectiveness of the lower dosage treatments (0.15, 0.75, and 3 g AI/ha) declined over time, so that by the end of the study, male moth catches in traps were significantly lower in plots treated with pheromone dosages ≥ 15 g AI/ha. The dosage of 75 g AI/ ha was initially replaced by a dosage of 37.5 g AI/ha in the USDA Forest Service Slow-the-Spread (STS) of the Gypsy Moth management program, but the program is currently making the transition to a dosage of 15 g AI/ha. These changes in applied dosages have resulted in a reduction in the cost of gypsy moth mating disruption treatments.

Mating Disruption for the 21st Century: Matching Technology With Mechanism

“…These were used because they were convenient, easy to install, and resulted in good rates of female recovery. However, as part of the study plot research activities in 2000 (see section 2000-Tethered Females Versus Mating Stations, p. 44), a direct comparison was made of mating success of females deployed in mating stations and females that were tethered with a thread and pinned to tree trunks (Tcheslavskaia et al 2005b). Mating success of tethered females averaged about twice that of females deployed in delta traps in untreated plots.…”

“…However, concern was raised that the traps may impede the ability of males to find and mate with females, resulting in artificially low levels of mating success. To test this, females were deployed in two different ways in the control plots of the test described above (Tcheslavskaia et al 2005b). In each plot, nine females were deployed in mating stations and nine were tethered using a thread with one end tied around the base of the forewing and the other attached to the bole of a tree with a push pin (Fig.…”

“…Since the only gypsy moth mating disruption product currently registered with US EPA is the Hercon Disrupt II flakes, another dose response test was conducted, this time with the flakes (Tcheslavskaia et al 2005b). The study was conducted in the Cumberland and Appomattox-Buckingham State Forests in central Virginia.…”

“…This rate was based on earlier dose response tests conducted under male moth densities that were much higher than those targeted for mating disruption in STS (Webb et al 1988). Therefore, a field test was conducted in 2000 to determine the efficacy of flakes applied at 15.2 g/acre compared to those applied at 30.4 g/acre (Tcheslavskaia et al 2005b). As part of the same test, 3M sprayable microcapsules were tested at 30.4 g AI/acre.…”

The effect of exposure to synthetic pheromone lures on male Zygaena filipendulae mating behaviour: implications for monitoring species of conservation interest

“…Consequently exposure to synthetic pheromones could prove detrimental to populations of rare insects occurring at low population densities and jeopardise their conservation (Sharov et al 2002;Witzgall et al 2008). The synthetic pheromone has to be present in sufficient quantities to successfully disrupt mating; for example a density of 27,300 wax droplet pheromone dispensers per ha is needed to effectively disrupt mating in Grapholita molesta (Busck, 1916) Tcheslavskaia et al 2005;Witzgall et al 2008). While the density of pheromone lures used in monitoring for conservation purposes is considerably lower, this is not to say that the populations will not be affected.…”