Trichogramma chilonis is a promising biocontrol agent against Tuta absoluta in China: results from laboratory and greenhouse experiments

Tuta absoluta, an economically important pest threatening the global production of tomato crops worldwide, has recently invaded China. Owing to insecticide resistance, alternative control options are needed within the context of integrated pest management (IPM) programs. Augmentative biological control using indigenous natural enemies is a promising tactic for managing T. absoluta in newly invaded areas. In this study, the host suitability of four commercialized Trichogramma parasitoids in China (T. dendrolimi, T. japonicum, T. chilonis, and T. ostriniae) on T. absoluta eggs was evaluated in laboratory conditions. The control effectiveness of the most promising Trichogramma species was further tested at different release densities and frequencies in a greenhouse experiment. We found that T. chilonis was the most promising species parasitizing T. absoluta eggs, showing the highest parasitism rate, emergence rate, and female offspring sex ratio. The greenhouse experiment indicated that 600,000 parasitoids/hectare (20 parasitoids/plant) was the most effective release density, reaching 76% control effectiveness. Release frequency significantly affected the parasitism rate in the greenhouse. Two releases of 300,000 parasitoids/hectare on Day 1 and Day 4 was the most effective strategy, compared to one release of 600,000 parasitoids/hectare on Day 1. Our findings showed that augmentative biological control of T. absoluta by native Trichogramma parasitoids T. chilonis in China is feasible, and it could be included as part of IPM package against T. absoluta in China.