DISRUPTION OF PHEROMONE COMMUNICATION IN PLATYNOTA-STULTANA (LEPIDOPTERA, TORTRICIDAE) IN GRAPE VINEYARDS

Leafroller, Platynota stultana Walsingham, pheromone-communication-dis ruption experiments were conducted in grape vineyards in the San Joaqu in Valley in California during 1993. Four synthetic pheromone componen ts were released, either singly or in various mixtures, into the atmos phere of the vineyards at predetermined rates from evaporation sources . These sources were attached to grape stakes at specified heights and spacings, in grids of 36 (6 X 6) evaporators. The numbers of male mot hs that located and were caught in female-baited traps in the centers of the evaporator arrays, compared with the numbers captured in simila r female-baited traps in untreated control areas, were used to calcula te the effectiveness of communication disruption. Most of the disrupti ve activity of the P. stultana pheromone was provided by the 2 compone nts that are found in greatest amounts in living female moths, (E)-11- tetradecenyl acetate and (Z)-11-tetradecenyl acetate. These components , combined in a 9:1 ratio, disrupted pheromone communication more effe ctively than did either component displayed alone. The extent of commu nication disruption was proportional to the amount of the pheromone co mponents released per hectare per day and was a function of both separ ation between evaporators and pheromone release rate from each evapora tor Ninety-nine percent disruption was obtained with the release of 6. 4 mg per hectare per day of the 9:1 blend of the 2 components. Most ma le P. stultana moths were active in the upper 3rd of the grapevine str ucture, and evaporators placed at this height were most effective in p reventing males from locating females.