Effects of Early Temperature Exposure on Diapause Development of Spruce Budworm (Lepidoptera: Tortricidae)

Abstract

Diapausing larvae of spruce budworm, Chotistoneura fumiferana (Clemens), were exposed in their early stage of development to different temperatures for various durations with or without subsequent cold storage periods at 2°C. The results suggest there exists an early developmental window or a phase, during which a diapausing larvae requires moderate temperatures to fulfill its development. Both degree and duration of temperature exposures during the early diapause stage had significant effects on diapause intensity and proportion of larvae capable of accomplishing diapause development under certain conditions. In general, longer duration of exposure to higher temperatures increases diapause intensity and reduces larval survival. Subsequent temperature treatment with the cold storage makes this phenomenon more obvious. Variation in emergence time was reduced substantially by a prolonged cold storage period. The implication of the results for the overwintering process of the species was discussed.