|Abstract or Summary
- Ovipositional behavior of the codling moth, Laspeyresia pomonella (L.), on several varieties of apples and pears grown in the Pacific Northwest was investigated during the spring/summer of 1979. Field studies showed that early in the season more eggs were laid on the Bosc variety than on several other apple and pear varieties. The number of eggs laid on all varieties, except the early ripening Gravenstein, increased as the season progressed. Additional investigations showed that significantly fewer eggs were laid on cultivars tested after their normal harvest periods. It was suggested that volatiles associated with fruit ripening, such as ethylene, may act as oviposition inhibitors. The location of eggs on apple and pear cultivars was also investigated. It was found that on apples more eggs were laid on the upper-leaf surface than the lower-leaf surface, while on pears the "preference" was reversed. This difference was probably due to the moths avoidance of the more pubescent under-side of apple leaves. The percentage of eggs laid on apple and pear fruits did not change significantly throughout the season. Contrary to previous reports, codling moths were found to "prefer" pear cultivars to apple cultivars when given a choice between the two. This "preference" was seen late in the season but not early in the season, indicating that it was a result of factors associated with the seasonal growth of the plants. Additional data suggested that it was a result of physical, as well as chemical, factors.
Levels of the known colding moth oviposition stimulant, alpha-farnesene, present in the epicuticular wax of apple and pear fruits, were determined twice during the season for each variety. The total amount per fruit and per unit area of skin was greater for all four pear varieties than the five apple varieties. On all cultivars, the total amount of alpha-farnesene on individual fruits increased with increasing fruit size. However, the amount of the sesquiterpene per cm² of fruit skin decreased from early to late season. Varietal differences in the concentrations of alpha-farnesene were positively related to differences in total oviposition per female on apple and pear cultivars.