| More than 50 chemical substances were prelim inarily tested their efficiency to enhance the toxicity of Bacillus thuringiensis against Heliothis armgera.Experiments of bolting synergists and killing insects were conducted in laboratory. Bioassy in laboratory was conducted according to the agricultural standard the People's Republic of China.Through first bolting and second bolting,the results showed that many compounds were able to increase their efficiency of insecticidal crystal protems for killing insects in varying degrees.Among these substances ,ZnCl2,NaH2PO4,CuSO4,Pengsuan and Avermectins have marked synergism effect.ZnCl2 was the most marked synergist and its ratio of synergism was 11.2 at the highest set concentration.The synergism effect of Pengsuan was in the next place and its ratio of synergism was 5.98 at the highest set comcentration.Then experiments of the rate of killing insects and compound bioassay were conducted with the five substances ,the results showed the highest rate was Pengsuan and after 24h themortality was 79.7% and after 72h the moutality of ZnCl2 was the highest ,96.6%.The ratio of synergism was the highest ,227.7,of ZnCl2 with Pengsuan . Bolting experiments in labortary and killing worms test liquid is to use as soon as it is mixed. Compound substances and Bt and put it for certain time,and then carry on bioassay to determine the influence to the activation of the spore of Bacillus thuringiensis . Results of the test indicate that compound thing and Bt having put some time will reduce the activation of the spore .So we should use the mixture as soon as we mixed.
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