Analysis of the Time-Concentration-Mortality Response of Nilaparvata lugens (Hemiptera: Delphacidae) to Paichongding.

Paichongding is an adicyclicnitromethylene neonicotinoid insecticide with a cis-configuration. Bioassay of paichongding was conducted against Nilaparvata lugens Stål under a laboratory condition. Mortality of N. lugens was analyzed by time-concentration-mortality (TCM) regressions based on the complementary log-log (CLL) model. The conditional mortalities of test individuals increased with the exposure time after treatments with different concentrations, showing that the speed of insecticidal action is concentration dependent. Meanwhile, the conditional mortalities of N. lugens increased as the concentrations of paichongding increased for all developmental stages from instars I-II to macropterous females. Correspondingly, LC(50) and LC90 values to N. lugens gradually decreased with the developmental stages, in which instars I-II were the most sensitive to paichongding, with LC(50) values of 6.31, 0.45, 0.09, and 0.03 mg/liter for 24, 48, 72, and 96 h after treatments, respectively, while macropterous females were the least sensitive among all developmental stages, with LC(50) values of 309.03, 11.48, 1.35, and 0.19 mg/liter at 24, 48, 72, and 96 h after the treatments, respectively. The time-concentration-mortality modeling was mathematically and biologically robust to evaluate the effects of paichongding on N. lugens. The results suggest that paichongding would be an effective alternative pesticide for controlling N. lugens considering its potent effects.