Functional response of Wolbachia-infected and uninfected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) to Asian corn borer, Ostrinia furnacalis Guenee (Lepidoptera: Pyralidae) eggs

Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) are haplo-diploid egg parasitoid wasps widely used as biological control agents against the Asian corn borer, Ostrinia furnacalis Guenee (Lepidoptera: Pyralidae). Two reproductive modes have been found in this species. Typically, female wasps produce haploid male offspring from unfertilized eggs and diploid female offspring from fertilized eggs (bisexual). However, they can also produce only diploid females when they are infected with Wolbachia, though the eggs are unfertilized (thelytokokous). To investigate the potential of a thelytokous Wolbachia-infected (TdW(+)) and a bisexual uninfected (Td) T. dendrolimi strain as inundative biocontrol agents, the functional responses of both strains toward their natural enemy (Asian corn borer) were evaluated at three constant temperatures (20, 25 and 30 degrees C). The results revealed two types of functional response for both strains: type II and III. TdW(+) strain displayed type II at 30 degrees C (high temperature) and III at 20 degrees C (low temperature) and 25 degrees C, while Td strain displayed type II at 20 degrees C and III at 25 degrees C and 30 degrees C. The comparison of functional response between two strains indicated TdW(+) and Td strain had no significant difference at 20 degrees C. However, the estimated host handling time of the TdW(+) strain was significantly shorter than that of the Td strain at 25 degrees C, and TdW(+) strain had significantly higher instantaneous search rate and shorter handling time than Td strain at 30 degrees C. Shorter host handling time and higher instantaneous search rate in thelytokous Wolbachia-infected T. dendrolimi showed that this strain might be more effective for controlling Asian corn borer.