Evaluation Of Methoprene For Control Of Lesser Grain Borer Tribolium Castaneum

Tribolium castaneum Herbst, the lesser grain borcr, has been reported as a serious initialpest of stored grains in various regions worldwide. In China, the borer mainly and thefemales distributes in South China. T.castaneum mainly feeds on corn, rice, wheat, and othercereals, and the females lay eggs on the surface of these grains. In order to provide scientificbasis for the application of methoprene, we systematicly examined the evaluation ofmethoprene for control of T. castaneum. The main rusults were as follows.The effects of methoprene on the longevity, fecundity and sex ratio of T. castaneum werestudied. The results showed that methoprene significantly affected the longevity andfecundity of T. castaneum, but these influences were subject to exposure periods. Thelongevity and fecundity generally decreased with an increase in the application rate ofmethoprene. However, there were no significant differences between the rate of1.5mg/kgand2.5mg/kg. The detailed results were as follows. T. castaneum were exposed for10d towheat treated with methorpen. The results showed that methoprene did not reduced theadult longevity. However, after20-day and30-day exposure, the longevity was significantlydecreased compared with the contorl. In addition, metorpene did not significantly affect thesex ratio of adult T. castaneum.The effects of methoprene on the development of the eggs, larvae and pupae of T.castaneum were examined, using direct contact and topical application. The results showedthat methoprene significantly inhibited the he development of eggs, larvae and pupae. Themain results were as follows. Methoprene applied at the range of0.00025mg/cm2to0.05mg/cm2remarkably reduced the egg hatch; the larvae failed to pupate at the applicationrate of0.032μg per larva; the number of adult emergence was significantly decrased bymethorpene applied at the range of0.004-0.032μg per pupa. In addition, the studies alsofound the pupae were more susceptible to methoprene than larvae.The efficacy of methoprene in controlling of T. castaneum was studied on store wheatunder two conditions, using a series general bioassays and simulation chambers. The resultsthat methoprene significant reduced the progeny population of T. castaneum under twoconditions. Methoprene applied at1.5mg/kg was the most suitable rate for suppressing T.castaneum progenies. In simulation chambers, for10-day exposure, methoprene applied at allrates did not significantly reduce the rate of weight loss in wheat under two conditions. For20-day and30-day exposure, the mortality of F0T. castaneum adults under unventilatedconditons was higer than that under ventilated conditions. However, methoprene did notremarkably influence the mortality of F0T. castaneum, and the fumigation effect was notexamined. In combined with unventilated conditions can remarkably reduce the parentaladults and progeny population of T. castaneum were examined under unventilated conditions,but they were subject to exposure periods. The present studies suggested that methoprenecombined with reclosable bag can be directly used to control T. castaneum in daily storage.Methoprene applied at1mg/kg caused>90%suppression of F1adult progeny of T.castaneum for150days to270days because of the temperature. The overall multivariateanova showed that the order of progeny reduction at different temperature(℃) was24>28>32>36. The results suggest that methoprene applied at≦24℃can be used to control T. castaneum on stored grains, especially on paddy.