Disruption of male oriental fruit moth to calling females in a wind tunnel by different concentrations of synthetic pheromone

Disruption of male Oriental fruit moth orientation to calling females was studied in a wind tunnel by surrounding calling female moths with septa loaded with synthetic pheromone. At the lowest loadings, 0.01 and 0.1 mu g, which produced release rates well below those of calling females, some males flew to septa instead of the females. At loadings of 1 and 10 mu g, which produced release rates close to those of a calling female, more than half the males flew to septa instead of the females, but there was little evidence of habituation at any of these loadings. At higher loadings, 100 and 1000 mu g, upwind flight of males was arrested, and many males remained inactive, indicating habituation. Preexposure of the males for 3 hr to ambient pheromone concentrations in the tunnel had no significant effect on numbers of disrupted males. However, at the 1000-mu g loading, most of the males that had been preexposed to the synthetic pheromone remained inactive. This may indicate a higher level of habituation than among males that had not been preexposed, most of which hew, although they subsequently showed flight arrestment. Levels of disruption were similar to those found for the spruce budworm in comparable experiments. In both species, less than 1% of the males were able to locate females when time-averaged concentrations of synthetic pheromone were above 20 ng/m(3). However, levels of inactivity and flight arrestment were higher among male Oriental fruit moths than among male spruce budworms, which may explain why Oriental fruit moths are more susceptible to disruption than are spruce budworms.