SEASONAL-VARIATION OF PHEROMONE CONCENTRATION IN MATING DISRUPTION TRIALS AGAINST EUROPEAN GRAPE VINE MOTH LOBESIA-BOTRANA (LEPIDOPTERA, TORTRICIDAE) MEASURED BY EAG

Spatial and temporal distributions and relative concentrations of the pheromone of the European grape vine moth Lobesia botrana (Lepidoptera : Tortricidae) were measured in mating disruption trials with electroa ntennograms. Measurements were carried out over several years during t he flight season of the two generations of this pest insect. In three consecutive years significantly higher mean relative pheromone concent rations were measured in summer during the flight of the second genera tion of L. botrana than in spring during the flight of the first gener ation (P < 0.001). The relative pheromone concentrations in 1989 reach ed a maximum between late July and early August, when the highest mean daily temperatures were registered. In addition to the differences in mean relative pheromone concentrations, the spatial and temporal dist ributions of the pheromone differed significantly between spring and s ummer. EAG recordings taken in summer showed high, uniform pheromone c oncentrations in the treated plots, whereas in spring strong temporal and spatial fluctuations were recorded. In a vineyard defoliated by a hailstorm, the mean relative pheromone concentrations measured in summ er were not significantly different from those measured in spring (P > 0.05), but were significantly lower than those of a nearby intact vin eyard (P < 0.001). The results provided additional evidence that folia ge is an important parameter determining mean pheromone concentrations and temporal and spatial distribution of pheromone in mating disrupti on trials.