The influence of the distance between traps on the results of pheromone monitoring of the gypsy moth Lymantria dispar (L.) (Lepidoptera: Erebidae) in the Southern Kyrgyzstan mountain region

Since one of the main goals of pheromone monitoring of forest insects is monitoring of the population density of the target species, correlations between catch efficiency of pheromone traps and population density began to be analyzed immediately after their widespread use in the forest protection practice. The absolute majority of authors that carried out such analysis, noted the absence of a direct correlation between population density and the results of pheromone monitoring of the gypsy moth Lymantria dispar (L.). In the mountainous conditions of Southern Kyrgyzstan, during the many years of pheromone monitoring (2001–2007), a high catch rate of males in traps was recorded, regardless of the population density. The goal of this study was to determine the effect of the trap layout and the distance between them on the results of pheromone monitoring. Three groups of trap lines were set up with a distance of 200– 250 m between the traps in a group. The first line of traps was set up in the belt of the pistachio light forest (800–1200 m above sea level), the second line was set up in the zone of mixed stands (1200–1600 m above sea level), and the third line was set up in the walnut belt (1600–2000 m above sea level). The elevation difference between the lowest and the highest trap was more than 700 m, and the distance between these extreme traps was more than 10 km. The results of this monitoring show that with stable air flows, males in the mass can travel up to two kilometers to a point source of the pheromone. Some males can travel up to 4 km. Males are capable of traveling long way, as indicated by the appearance of males in the uppermost traps of the upper zone during the beginning of their summer flight at the lower zone. The results of this study confirm our earlier conclusion about the significant influence of stable air flows on the results of pheromone monitoring. Under these conditions the distance of 2 km or less between traps leads to significant decrease in the objectivity of monitoring results.

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