Method of testing insecticide susceptibility of Stenotus rubrovittatus (Hemiptera: Miridae) by topical application

Abstract

Appropriate droplet size and the preferred sex and age of insects for insecticides used in topical application were investigated to standardize the method of testing the susceptibility of Stenotus rubrovittatus (Matsumura). The overflow of acetone droplets applied on the notum of the thorax of S. rubrovittatus adults occurred when the droplet size exceeded 0.20 μl per insect, and the overflow occurred more frequently in males than in females. No effect of acetone solution on mortality was observed at less than 0.20 μl droplet size per insect within 72 h after treatment. The LD50 values and relative potencies of fenitrothion 24 and 48 h after treatment were almost the same in each sex. The fenitrothion susceptibility of males was twice higher than that of females. The fenitrothion susceptibility increased with age after emergence. However, there were small differences in LD50 values and relative potencies between 4–7 and 8–11 days after emergence because the females 4–11 days after emergence had a small difference in body weight. These results led us to conclude that the recommended size of acetone droplets per insect is less than 0.20 μl and that it is suitable to use S. rubrovittatus females 4–11 days after emergence for topical application.