Ksenia Tcheslavskaia

Optimization of pheromone dosage for gypsy moth mating disruption

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.

Persistent effects of aerial applications of disparlure on gypsy moth: trap catch and mating success

In forest plots treated aerially with a plastic laminated flake formulation (Disrupt® II) of the gypsy moth sex pheromone disparlure to disrupt gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), mating was monitored the year of treatment and 1–2 years after treatment to determine the effects of the treatment on suppression of trap catch and mating success. In the year of treatment, there was a greater than 95% reduction in trap catch and a greater than 98% reduction in mating success compared to controls. One year after treatment at a dosage of 37.5 g active ingredient (a.i.) ha−1, trap catch was reduced by 46–56% and mating success was reduced by 60–79%. Both trap catch and mating success were significantly reduced compared to controls in plots treated 1 year previously at 15 g a.i. ha−1. Trap catch, but not mating success, was significantly reduced 2 years after treatment at 37.5 g a.i. ha−1. The efficacy of mating disruption (MD) treatments in the Slow‐the‐Spread of the Gypsy Moth program was significantly reduced 2 years compared to 1 year after treatment. No such reduction was observed in plots treated with aerial applications of Bacillus thuringiensis kurstaki. The higher apparent efficacy of MD treatments 1 year after application may result to some extent from the suppression of moth capture in pheromone traps from the persistent effects of the previous years treatment.

Effects of intentional gaps in spray coverage on the efficacy of gypsy moth mating disruption

Abstract:  The study was conducted during 2001 and 2002 in forested areas in Virginia, US to examine the effects of gaps in coverage of pheromone on gypsy moth, Lymantria dispar (L.) (Lep., Lymantriidae), mating disruption. Gypsy moth male moth catches in pheromone‐baited traps were significantly reduced in plots treated with the gypsy moth sex pheromone, disparlure, at an overall application rate of 37.5 g of active ingredient (AI)/ha but with untreated gaps of 30 or 90 m between 30‐m wide treated swaths. In one of the two plots with 90 m gaps, significantly more males were captured in traps in the untreated areas compared with the treated areas within the plot. However, in another plot, significant differences in trap catches between treated and untreated areas were not observed. No difference in male moth catches in the pheromone‐baited traps was observed between treated and untreated areas within the plots treated with 30 m gaps. Female mating success did not differ significantly between treated and untreated areas within the one plot in which it was measured. These results suggest that it may be possible to lower costs associated with gypsy moth mating disruption applications by alternating treated and untreated swaths, which would reduce flight time and fuel costs, without a reduction in efficacy.

Effect of Synthetic Pheromone on Gypsy Moth (Lepidoptera: Lymantriidae) Trap Catch and Mating Success Beyond Treated Areas

Abstract Racemic disparlure sprayed at doses of 37 to 75 g/ha (AI) for mating disruption of gypsy moths, Lymantria dispar (L.), interfered with male moth search behavior outside of treated plots. Counts of feral male moths in pheromone-baited traps and the number of recaptured laboratory-reared moths gradually increased with increasing distance from treated areas. In most cases this effect was observed up to 250 m from treated plots. However, in one location it extended to 600 m along a narrow valley. The proportion of tethered females that mated during 1-d exposure increased gradually with increasing distance from treated plots. The relationship between male moth capture rates in pheromone traps and mating success of tethered females near treated plots was the same as the one observed in previous studies in pheromone-free areas.

Diffusion of Insect Pheromones in a Forest Canopy: Co-Located Tracer/Electroantennogram Experiments

Sulfur hexafluoride (SF6) is a tracer gas that has been widely used to simulate behavior of air pollutants in the atmosphere. In this study, however, tracer experiments were conducted to study diffusion of insect pheromone through a forest canopy. Experiments were performed during morning and afternoon hours in August of 2003 at a forested field site near Pellston, Michigan. An SF6 source was collocated with a gypsy moth pheromone source, and concentration data for both gases were collected downwind with near-instantaneous equipment at a source-to-receptor distance of 5 m. In addition, a sonic anemometer was used to measure turbulent changes in horizontal and vertical winds throughout the study. The results illustrate the use of SF6 as a surrogate for insect pheromone, and to evaluate the performance of a new, portable, electroantennogram (EAG) device.