Abstract: Trichogramma chilonis (Hymenoptera: Trichogrammatidae) is an important parasitoid of many lepidopterous pests on various crops. In order to determine the safety of chlorantraniliprole to the parasitoid, the acute toxicity of chlorantraniliprole to the adults was measured, and the behavioral effects of chlorantraniliprole at field-recommended concentrations on T. chilonis were evaluated in laboratory. The results showed that chlorantraniliprole was at a low risk level to T. chilonis with LC₅₀ of 177 mg/L, but long-term treatment significantly reduced the lifespan by 1.75 d. The parasitoid exhibited Holling type Ⅱ functional response, with an instantaneous attack rate of 1.343, a maximum parasitism capacity of 57.471 eggs/d, which was reduced by 1.25 times when the wasps were treated with chlorantraniliprole. The treatment not only reduced the host selection rate of T. chilonis adults significantly, but also significantly extended the host search and location time. Although the treatment had no significant effect on the mating success rate, it significantly extended the mating detection and courtship time, and decreased the duration of copulation time. The treatment had no significant effect on oviposition duration and offspring sex ratio, but significantly increased the pause time during ovulation. In conclusion, the field recommended concentration of chlorantraniliprole has a negative effect on host search and location and oviposition behavior of T. chilonis, which has to be considered in balancing the compatibility of biological and chemical control.

Key words: Trichogramma chilonis, sublethal effect, behavioral observation, chlorantraniliprole