Laboratory induction and termination of aestivation in Platygaster demades Walker, an important parasitoid of Dasineura mali Kieffer

Abstract

Dasineura mali Kieffer (Diptera: Cecidomyiidae) is an important pest of apple in Europe, North America and New Zealand and contaminates fresh fruit. Platygaster demades Walker (Hymenoptera: Platygasteridae) is the most important parasitoid of D. mali. A high percentage of P. demades individuals enter aestivation in the field which lasts more than 20 weeks, resulting in outbreaks of the pest in the summer. Therefore, the ability to induce and terminate aestivation in the laboratory is important for the improvement of biological control of D. mali using P. demades. Our results show that the highest proportion of P. demades individuals entered aestivation at 14:10 h (L:D) and 25 °C with the critical day-length and temperature for aestivation induction being 13.8 h light and 22.8 °C, respectively. The best aestivation termination condition was 12 h light + 15 °C. It is suggested that: (1) the aestivation peak in the field that occurs in mid-summer may be caused by environmental conditions P. demades have experienced in the spring; (2) laboratory colonies of P. demades should be maintained between 15 and 20 °C with a photoperiod of 12:12 h (L:D) to avoid the occurrence of aestivation; (3) treating P. demades at 14 h light + 25 °C for 15 days is sufficient to induce aestivation; and (4) aestivation can be terminated in 10–13 weeks at 12 h light + 15 °C.