Impact of insect growth regulators on reproduction and life stages of Tribolium Castaneum (Coleoptera: Tenebrionidae)

Abstract

Tribolium castaneum is devastating cosmopolitan insect pest of stored grain. The present study investigated the impact of three insect growth regulators on different life stages of T. castaneum. Percent mortality (%) induced was observed at 0.75. 1.25, 2.5, 5, 10, and 20 ppm doses of each IGR after 7, 14 and 21 day exposure. In addition to larval and parental mortality, progeny suppression data was also recorded. The larvae of the 2nd instar were more susceptible to lufenuron, with mortality reaching 100% at 10ppm even after a 14-day interval. In the case of pyriproxifen, 2nd instar did not responded to all dose rates until 14 days however 21 days, statistically corresponding 2.5 to 10 ppm dose rates was detected. At 20 ppm, methoxy fenazide resulted in 92 percent mortality of 2nd larval instar mortality, and the larvae responded to all dose rates at all exposure intervals that varied significantly among themselves. The mean mortality of the 4th instar larvae at 20 ppm for lufenuron after a 21-day interval was 90%, which was not significantly different from the mortalities (62 and 80%) at the same dose rate after 7 and 14 days, respectively. All the IGRs were very effective in progeny suppression (>80%) and complete progeny suppression (100%) was observed in adults treated with methoxyfenazide and lufenuron at 2.5 and 10 ppm doses, respectively. It is concluded that all the screened IGRs were effective in progeny suppression and in some cases, complete progeny suppression was achieved