The Studies Of Bacillus Thuringiensis Against Stored Grain Instects

Application of Bacillus thuringiensis in the control of stored grain pests was studi es in this article.There are four aspects in this paper. The one is incubation of Bacill us thuringiensis and culture, extraction insecticidal crystal protein from Bt. Another res earch is bioassay methods of Bt stored grain insects. The third one is to bioassay the toxicity of Bt against stored grain pests. The last aspect is to bioassay insecticidal cr ystal protein from Bt stored grain pests.Experimental work about expansion of Bt strains and culture, Bt insecticidal cryst al protein extraction and electrophoresis and other biological aspects are the preparator y work. The completion of these works is the foundation for bioassay on stored grain pests with Bt and Bt insecticidal crystal proteins.In this study, we selected3bioassay methods on stored grain pests with different living habits. They are mixed grain method, mixed feed method, and mixed drug she et method, the first two methods by definition is feed pests with grain or feed, they a re mixed withBt fermentation liquid or Bt insecticidal crystal protein. Then detect gro wth of the insect pests, filter out effective Bt or Bt insecticidal crystal protein to cont rol stored grain pests.Mixing sheet method is a new biological methods study and formulate in our lab oratory. This method is established for quantitative determination of lethal dose of sto mach poison on stored grain pests. In this method stored grain insects are feed with a rtificial mixed drug sheet. Every mixed drug sheet were weighted before and after fee ding to determine the feeding dose of feed sheet. Then calculate the lethal dose of pe sticides on stored grain pests.In our research40Bt strains were selected, and preliminary bioassay was carried on5kinds of stored grain insects. They are Plodia interpunctella larvae, Tribolium castabeum larvae, R. dominica adults, Oryzaephilus surinamensis adults, Lasioderma se rricorne larvae. Biometrics on Plodia interpunctella larvae, Tribolium castabeum larvae, Lasioderma serricorne larvae used mixed feed method. Biometrics on R. dominica us ed mixed grain method, And Lasioderma serricorne larvae used mixed drug sheet met hod. We found that mortality rate of Plodia interpunctella larvae is up to93.3%. Cyt otoxic effects on Tribolium castabeum larvae, R. dominica, Lasioderma serricorne larv ae adults is not so obvious. There is no Cytotoxic effects on Oryzaephilus surinamens is adults.We found5effective Bt strains through40Bt strains.5kind of Bt insecticidal c rystal protein were extracted, and bioassay on4kind of stored grain pests was carried on. Cytotoxic effects of SC-1B3Bt insecticidal crystal protein on Plodia interpunctella larvae is up to100%. Cytotoxic effects of5kind of Bt insecticidal crystal protein o n Tribolium castabeum larvae is up to41.7%and R. dominica is up to31.7%, How ever cytotoxic effects is not obvious on Lasioderma serricorne larvae.