SPATIAL-DISTRIBUTION OF PHEROMONE IN VINEYARDS TREATED FOR MATING DISRUPTION OF THE GRAPE VINE MOTH LOBESIA-BOTRANA MEASURED WITH ELECTROANTENNOGRAMS

The spatial distribution of the pheromone of the grape Vine moth, Lobe sia botrana (Lepidoptera: Tortricidae), was measured in vineyards trea ted for mating disruption by using an electroantennogram technique (EA G). Five hundred dispensers per hectare, each containing 0.1 g of the main component of the sex pheromone (E,Z)-7,9-dodecadienyl acetate (E7 ,Z9-12:Ac) were evenly distributed in the experimental vineyards. The EAG amplitudes measured in the experimental plots were transformed int o relative pheromone concentrations by means of a calibration curve. M ean relative pheromone concentrations in the center of a treated plot reached 2.31 x 10(-4) relative units. No significant differences in th e mean relative pheromone concentrations were found between replicate plots (P > 0.01). The mean relative pheromone concentrations measured within one plot along a transect at 5-m intervals also showed no signi ficant differences between the sites. These results indicate that insi de the borders of treated areas the pheromone was evenly distributed. No sites with significantly lower pheromone concentrations, frequently assumed to be the cause for higher trap catches in some areas, were f ound. However, the mean relative pheromone concentration rapidly decli ned more than 100-fold outside the border of the treated plot. At 10 m from the treated area, the EAGs showed no significant difference comp ared to the EAGs recorded in an untreated area. A rapid drop in the me an relative pheromone concentration was also found on a vertical trans ect through the canopy of the vineyard. Measurements in an untreated c ontrol block gave a mean antennal response approximately 1000-fold low er than in a nearby pheromone treated plot. The significance of the va riation in the pheromone distribution for the success of the mating-di sruption method is discussed.