Mating Disruption as an Effective Method for Controlling Lymantria dispar (L.): Results of the First Investigation in Europe

In a three-year study, we investigated the efficacy of mating disruption (MD) on the spongy moth, Lymantria dispar L. in a forest complex in Slovenia. We included two treatments in the experiment: a negative control and a MD-treated area, where we used an MD product formulated as a biodegradable gel (water based, biodegradable). We applied the gel to the trunks of the forest trees (33.3 g active ingredient/ha) once per season, specifically on 4th August 2022, 28th June 2023, and 24th June 2024. To evaluate the method’s performance, pheromone traps were utilized in both treatments. The data indicate consistent effectiveness throughout the three-year period, characterized by the minimal male captures observed in the MD treatment areas after the gel was applied. The first moths were captured in the traps at DD (Degree-Day) values ranging from 661.7 to 773.3 and continued to be captured up to DD values between 1576.1 and 1642.8. Following the application of the MD, the population in the MD treatment was reduced by 100% in the first year. In the second year, the reduction was 96.33%, while in the third year of the experiment, the number of captured moths in the MD treatment was 99.20% lower compared to the control. Considering the overall data, the method disrupted Lymantria dispar male orientation effectively. Moreover, we also feel that these results show the most promise for using this method in urban and suburban areas, where L. dispar larvae can cause allergies in humans and animals and where the use of insecticides is reduced.