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Stimuli from the plant Camellia japonica that influence the host-finding and acceptance behaviors of adult females of the generalist herbivore Epiphyas postvittana were investigated. In a binary choice test in a small (35-cm-diam.) arena, females discriminated between a plant and a laminated card model, laying many more eggs on the plant. Observations of females showed that the greater number of eggs laid on the plant were primarily due to on-plant behaviors, with females spending significantly more time per visit on the plant than on the model. Interestingly, females landed a similar number of times on the plant as on the model, suggesting that volatile chemicals from the plant did not influence host-finding. This observation was further supported by wind-tunnel studies, in which females showed little or no upwind flight activity in response to plants and laid similar numbers of eggs on upwind and downwind plants. Leaf surface texture, a combination of smoothness and fine structure (consisting of the midvein and other raised leaf veins), was found to stimulate egg laying by females. Methanol, dichloromethane, and pentane extracts were made of the waxes on the leaf surface. Of these three extracts, only the nonpolar (pentane) one stimulated egg laying by females. Although we did not find a role for volatile plant chemicals in host finding, they appeared to stimulate increased egg laying when the female was on the plant. It appears likely that these chemical and tactile stimuli in C. japonica are general stimuli, which may be found in a large number of plants and, in combination with the feeding preferences of the larva, may explain the generalist herbivorous nature of this pest.

Uptake and release of pheromone and behavioral inhibitor ofEpiphyas postvittanna by apple leaves was tested using field electroantennograms (EAG), trap catches to synthetic lures and virgin females, and chemical analysis. Trap catches in single apple trees (N=3) were monitored for six cycles of six days' duration, using delta traps baited with synthetic pheromone. Polyethylene dispensers (0, 1, 10 per tree) releasing pheromone and inhibitor were present for only the first three days of each cycle. Application of 10 dispensers per tree resulted in complete disruption of trapping, which continued for one day after dispensers 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 catch. In contrast, the presence of only one dispenser per tree led to 0-20% of control catches, but on the three nights following dispenser removal catches were 35, 40, and 80% of the control catch. Field EAGs indicated significantly higher relative pheromone concentrations in the trees with 10 dispensers present, compared to trees with single dispensers, but removal of dispensers produced no detectable treatment effect compared to the control trees one day after dispenser removal. In a second experiment, releases of marked male moths into apple orchard plots following the removal of polyethylene dispensers (1 hr earlier that day) resulted in significantly lower catches in traps baited with virgin females in blocks that had been treated, compared to controls. Recovery of pheromone by solvent washing of leaves loaded with 50 µg of the main component of the sex pheromone (1.26 µg/cm(2)) was low (2.5%). Leaves held in a pheromone-saturated atmosphere were loaded with 0.045±0.007 µg pheromone/cm(2). Analysis of apple leaves taken from a pheromone-treated tree at different distances from the pheromone dispenser showed a decay of the pheromone load per square centimeter with increasing distance from the dispenser, as previously indicated by EAG.

Inhibition of the behavioral responses of maleEpiphyas postvittana moths by theZ isorner of the major component of the sex pheromone,E11-14: OAc, was studied in a wind tunnel. Inhibition was detectable at a Z isomer concentration of 10% that of the major component and was greatest when it was added to the same source as the pheromone. Inhibition declined rapidly as the inhibitor was moved across-wind away from the pheromone source but was largely maintained when the sources were separated upwind or downwind. The results showed that the insects possess a high degree of temporal resolution for odor plumes of different composition.

Two compounds, (E)-11-tetradecen-1-yl acetate and (E,E)-9,11-tetradecadien-1-yl acetate, have been identified in extracts of females of the lightbrown apple moth,Epiphyas postvittana (Walker). The two compounds are active as a coalitive pair and are present in extracts of females in a ratio of about 20∶1.