VARIABLES AFFECTING PHEROMONE CONCENTRATION IN VINEYARDS TREATED FOR MATING DISRUPTION OF GRAPE VINE MOTH LOBESIA-BOTRANA

Airborne pheromone concentration in a field is one of the most importa nt variables for the successful application of mating disruption in pe st control. In the present paper, we estimated the pheromone concentra tion with field EAG recordings in vineyards and investigated parameter s affecting concentration. Pheromone concentration showed a positive c orrelation with number of dispensers per hectare (= number of point so urces). A twofold increase in the absolute number of dispensers per he ctare with a constant number of point sources (two dispensers at the s ame location) did not significantly affect relative pheromone concentr ation. Measurements carried out in plots where dispensers had been app lied at different heights showed highest relative pheromone concentrat ions in plots with dispensers at 0.1 m and 1.4 m above the ground. Tho se concentrations were not significantly different from each other, bu t were significantly higher than in plots where dispensers had been pl aced at a height of 2 m. Foliage of grape vines substantially affected the development of high pheromone concentrations. In summer, in viney ards with fully developed leaf canopy, significantly higher pheromone concentrations could be measured shortly after application of the disp ensers compared to vineyards in spring with sparse vegetation. The dec line of pheromone concentrations after removal of dispensers is signif icantly prolonged in full vegetation, showing the impact of plant cano py on pheromone concentrations. In contrast, ground cover between the grapevine rows did not significantly affect mean pheromone concentrati ons.