Sub-zero cooling synchronizes post-diapause development of codling moth, Cydia pomonella

Sub-zero cooling treatments of -10 degree C and -15 degree C for 2-6 days were evaluated as a means of meeting the chilling requirement of diapause and to synchronize post-diapause development in larvae which were held in diapause for less than 6 months. Sub-zero cooling did not affect male longevity. After six months in diapause, diapause/cooled females were longer lived than diapause control females but not longer than non-diapause females. In general, diapause-cooled males passed more spermatophores than males from control diapause and non-diapause groups. In general, sub-zero cooling did not consistently affect fecundity and % egg hatch. Non-diapause females laid the most eggs after six months in diapause, and diapause-cooled females laid the most eggs after seven months in diapause. The duration of sub-zero cooling had a significant effect on post-diapause emergence in relation to the duration that the larvae were in diapause. Sub-zero cooling for 4 days at -10 degree C significantly reduced the number of days to adult emergence of larvae which had been in diapause for 0-4 months. Sub-zero cooling at -15 degree C for durations of 2, 4, and 6 days had more variable effects on emergence, but in most cases, sub-zero cooling reduced the amount of time to and span of adult emergence.