SUMMER DIAPAUSE IN PHYLLONORYCTER BLANCARDELLA (FABR.) (LEPIDOPTERA: GRACILLARIIDAE) IN ONTARIO
AbstractThe life stages of Phyllonorycter blancardella (Fabr.) were monitored in an orchard at Guelph, Ontario in 1981 and 1982 and the results showed discrepancies with the previous concept of a trivoltine species occurring throughout its range in eastern North America. Sleeve cages were used to monitor the development of the second, mid-summer generation of leaf miners in a low-maintenance orchard at Guelph in 1982 and 1984 and 2 commercial orchards at Simcoe, Ontario in 1984. The flight period of the first-generation adults occurred over approximately a 6-week period. From eggs laid early in the flight period, a large proportion of the larvae developed quickly and emerged to give a second-generation adult flight. As the flight period continued, there was an increase in the number of progeny whose development was delayed in the early instars. These larvae did not pupate until late fall and overwintered as pupae. Of the second-generation larvae, about 70–90% at Guelph and 35% at Simcoe had a delayed development (summer diapause) and formed a large proportion of the overwintering population.