Study On Ovipitional Inhibition By Active Substances From Garlic Essential Oil Against Sitotroga Cerealella

The Angoumois grain moth,Sitotroga cerealella Olivier,is a serious stored grain pest in the world,especially in China.At present,chemical insecticides,which may cause"3R" problems easily,are still the key methods to control S.cerealella.It's urgent to find an cost-effective and environmentally friendly method to solve these problems.For its virtue of safe,slow evolvement of insect resistance,the behavior manipulation method has gradually becoming an accepted tactic in integrated pest management.In this study,the effect of the active substances from garlic essential oil on the fecundity and mating behavior of S.cerealella were tested.Meanwhile,the morphology and location of female sex pheromone gland were studied by histological,microscopic techniques and Gas Chromatography-Mass Spectrometry(GC-MS).The effect of diallyl trisulfide on the titer of main sex pheromone components in the crude extracts of female sex pheromone gland were also quantified.The results will help to provide a theoretical foundation for controlling the moth with botanical components based on the behavioral manipulation.The main research results are as follows:1.The sublethal concentration(LC20)of two major components of garlic essential oil[diallyl disulfide(DD)and diallyl trisulfide(DT)],were determined through the fumigation method in a sealed jar,which were 0.030 ?L/L,0.015 ?L/L,respectively.Additionally,the morphology of spermatophore,eggs laid by mated and unmated females were all observed.Based on the results of bioassay and morphology study,the moth's fecundity,number of spermatophores,and the percentage of viable eggs were tested after treated with the sublethal concentration(LC20)of DD and DT.The results showed that,the anount of eggs,mating frequency and the percentage of viable eggs of two treated groups were all significantly decreased compared with the control(P<0.05).2.Observation on the moth's circadian mating rhythms,mating frequency,calling periodicity,courship rate and mating duration were conducted after the moths were fumigated with sublethal dose of DD/DT,and results indicated that both the two components had effect on these parameters above,especially for the DT.Compared with controls,the peak of moth's mating for the group treated with DT came ahead of time(P<0.05),while it was put off in the following three days,among which they were significantly different from the controls in the 2nd and 3rd day(P<0.05).Both males and females S.cerealella possesses the characteristics of multiple mating behavior,and the mating frequency graduatlly increases over time.But after fumiigation with DT,the increasing rate of moth's mating frequency was very slow compared with controls,which was notably different from controls(P<0.01).Similarily,the moth's calling rhythm had been changed after treated with the two substances.However,although the total calling percentage at the first day had no difference between the groups treated with DT and control groups,but that droped significantly with the increase of treated time,and there were significantly different compared with controls in the following three days(P<0.05).Also,the DT had a negative effect on the mating duration of S.cerealella.Through the continuous observation,we found the first day's mating duration of DT group significantly shortened when compared with control(P<0.05).The change tendency of circadian mating rhythms,mating frequency,calling periodicity,courship rate and mating duration after fumigated the moths with DD were same as those of DT treatment.3.The location and morphology of female sex pheromone gland were studied by histological,microscopic techniques and GC-MS.Results showed that the sexual gland of S.cerealella was an eversible sac of glandular epithelium situated dorsally in the intersegmental membrane between the 8th and 9th abdominal segments.Meanwhile,the sex pheromone was extracted at 2,7,8,9 h after fumigated the virgin female moth with the sublethal doses of DT respectively.Then the titer of sex pheromone was analyzed by GC-MS.The results revealed that the content of sex pheromone extracted at 2h after treatment was slightly more than that of control,however,that extracted at 8h after treatment was significantly lower than that of control(P<0.05).