Overwintering and cold tolerance in pupae of large cabbage white, Pieris brassicae (Lepidoptera: Pieridae) in Iran

Large cabbage white, Pieris brassicae, is a major pest of Brassicaceae family which overwinters as pupa on different shelters. In spite of increase in oilseed cropping area, there is little information available about its overwintering condition. In this study, overwintering pupae were collected during November 2012 to April 2013 and the diapause conditions, the whole body supercooling point (SCP), cold tolerance at subzero low temperatures (-10, -15, -20, -25 and -30°C) as well as lower lethal temperatures (Ltemp50 and Ltemp80) were investigated. The results showed that these pupae were in the main phase of diapause during three months of winter when the highest level of cold-hardiness capacity was observed. Also, the SCPs were significantly decreased and reached near to Ltemp50 at this time. Therefore, it could be concluded that these pupae use freeze avoidance strategy and there is a close linkage between diapause and cold-hardiness in this species, so, the highest level of cold tolerance could be expected during the deep phase of diapause in winter.