Temperature dependent emergence and survival of Platygaster demades (Hymenoptera: Platygastridae), parasitoid of apple leaf curling midge

Abstract

Abstract The influence of temperature on the emergence and adult longevity of Platygaster demades Walker, an egg parasitoid of apple leaf curling midge (ALCM) was determined at five constant temperatures in the laboratory: 11, 15, 19, 23, and 27 °C. Apple leaves infested with second and fourth generation ALCM larvae were collected from three regions in New Zealand. Emergence of both ALCM and P. demades at the five temperatures were compared across two generations and three locations. Adult P. demades were fed with honey-agar diet and tested for longevity without exposure to ALCM eggs. Ten females reared at each temperature were allowed to live full life spans, and once dead were dissected to measure potential fecundity. The development period of P. demades in soil increased with increasing temperature but fewer emerged at 11 and 27 °C. The optimum temperature was 19 °C. Significant differences in development and emergence rates of P. demades between the second and fourth generations with temperature were detected ( P = 0.003), although no differences in either were found between locations ( P > 0.400). The highest longevity for females (47.9 ± 5.5 days) and males (31.3 ± 5.3 days) was recorded at 11 °C. Longevity decreased with increasing temperature. Life time fecundity did not change with age ( P = 0.888) and an average female carried a mean pre-ovipositional load of 1380 ± 263 eggs. Temperature has been considered one of the most important physical factors to influence asynchrony between second generation populations of P. demades and ALCM. Impacts of high longevity and fecundity on the ability of the parasitoid to overcome the synchrony are discussed.