Comparison of thermal performances of two Asian larval parasitoids of Drosophila suzukii.
Ganaspis brasiliensis Ihering and Leptopilina japonica Novković & Kimura (Hymenoptera: Figitidae) are candidates for biological control of the spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilae), an invasive pest originally from East Asia. Developmental time and offspring survival from egg to adult, and fecundity (measured as adult offspring production/female wasp) of a Chinese and a South Korean population of both species were assessed at different constant temperatures. Development time decreased with increasing temperature from 17.2 to 27.5°C; at 29.3°C no parasitoid completed development. Temperatures below 17.2°C triggered a facultative diapause in both species, and this cold temperature response varied among populations of different origin: South Korean populations of G. brasiliensis and L. japonica entered diapause at 17.2°C, whereas only a proportion of their Chinese counterparts entered diapause at the same temperature. No significant differences in offspring survival and fecundity were detected between populations in the mid-temperature range. However, fecundity at 15.9°C was higher for South Korean populations of G. brasiliensis and L. japonica compared with their Chinese counterparts, suggesting that the host location and oviposition behavior of the searching females was less affected by the cold temperature and/or their eggs had better cold hardiness. These variations in response to cold temperatures need to be further investigated and their ecological significance assessed to better understand performance of G. brasiliensis and L. japonica in those invaded regions where control is needed.