APPLE FOLIAGE ENHANCES MATING DISRUPTION OF LIGHT-BROWN APPLE MOTH

Uptake and release of pheromone and behavioral inhibitor of Epi phyas postvittanna by apple leaves was tested using field electroantennogram s (EAG), trap catches to synthetic lures and virgin females, and chemi cal analysis. Trap catches in single apple trees (N = 3) were monitore d for six cycles of six days' duration, using delta traps baited with synthetic pheromone. Polyethylene dispensers (0, 1, 10 per tree) relea sing pheromone and inhibitor were present for only the first three day s of each cycle. Application of 10 dispensers per tree resulted in com plete disruption of trapping, which continued for one day after dispen sers were removed. Over the three nights following the removal of the dispensers (days 4-6), trap catch was 0, 10, and 15% of the control ca tch. In contrast, the presence of only one dispenser per tree led to 0 -20% of control catches, but on the three nights following dispenser r emoval catches were 35, 40, and 80% of the control catch. Field EAGs i ndicated significantly higher relative pheromone concentrations in the trees with 10 dispensers present, compared to trees with single dispe nsers, but removal of dispensers produced no detectable treatment effe ct compared to the control trees one day after dispenser removal. In a second experiment, releases of marked male moths into apple orchard p lots following the removal of polyethylene dispensers (1 hr earlier th at day) resulted in significantly lower catches in traps baited with v irgin females in blocks that had been treated, compared to controls. R ecovery of pheromone by solvent washing of leaves loaded with 50 mu g of the main component of the sex pheromone (1.26 mu g/cm(2)) was low ( 2.5%). Leaves held in a pheromone-saturated atmosphere were loaded wit h 0.045 +/- 0.007 mu g pheromone/cm(2). Analysis of apple leaves taken from a pheromone-treated tree at different distances from the pheromo ne dispenser showed a decay of the pheromone load per square centimete r with increasing distance from the dispenser, as previously indicated by EAG.