Pupal diapause development and termination is driven by low temperature chilling in Bactrocera minax

Abstract

Bactrocera minax is a major citrus pest in China, Bhutan, and India. It is univoltine and exhibits pupal diapause during winter. To better understand pupal diapause in this pest, we investigated pupal survival and pupal developmental duration under field and laboratory conditions. Specifically, we tested if pupal chilling was required for diapause development and termination. Nearly all mature larvae collected at the end of the citrus season entered pupal diapause. For pupae exposed in the field, natural chilling for less than 3 months resulted in more than 70 % mortality. However, exposure to winter conditions for 3 months or more both decreased pupal mortality and developmental duration when pupae were returned to the laboratory and held under constant temperature (25 C). When pupae were gathered from the field in November and exposed to different chilling regimes in the laboratory, the chilling duration (30 vs 60 days) had significantly more impact on pupal survival than the specific chilling tem- perature (6, 8, 10, or 12 C constant). However, both chilling duration and chilling temperature impacted on the pupal developmental duration, with longer chilling dura- tion and higher temperatures decreasing pupal develop- mental duration. In conclusion, we demonstrated that pupal diapause development and termination in B. minax is strongly influenced by chilling conditions. Increasing cold exposure led to significantly and consistently faster adult eclosion and improved synchronization of adult emer- gence. This knowledge will help with the laboratory rear- ing of B. minax, an essential step in the long-term management of this pest.