Analysis of time- and concentration-mortality relationship of nitenpyram against different larval stages of Nilaparvata lugens (Hemiptera: Delphacidae).

Bioassay of nitenpyram was conducted on the planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) in the laboratory by using the rice-stem dipping method. The resulting data were analyzed using the complementary log-log time-concentration-mortality modeling technique, yielding the parameters for time and concentration effects of nitenpyram against N. lugens instars. The LC50 values to instars I and II estimated for 24, 48, and 72 h after treatment were 1.03, 0.27, and 0.11 mg/liter, respectively. These values were lower than those for instars III and IV and instars V at the same times. The estimates of LT50 for instars I and II were decreased from 69.06 to 16.22 h with the increasing concentration from 0.125 to 2 mg/liter; the same estimates for both instars III and IV and instars V at the concentrations of 1-2 mg/liter were close to each other, ranging from 33.11 to 44.16 h, much higher than the values of instars I and II at the same concentration. Based on the time-concentration-mortality relationships fitted and the virulence indices (LC50 and LT50) estimated, nitenpyram is a promising pesticide for N. lugens control.