The Research On The Feasibility Of Matrine And A Zadirachtin Against Stored-grain Insects

In this study,two single agents,matrine and azadirachtin were compounded for synergism test,and the optimal ratio was obtained for verifying whether 1%matrine-azadirachtin that was formerly studied was suitable for the control of stored grain pests or not.The control efficiency of matrine-azadirachtin on stored grain pests,such as Sitophilus zeamais and Tribolium castaneum,was investigated by mixing with grain. The minimum effective concentration of 1%matrine-azadirachtin was determined.The control efficiencies of matrine-azadirachtin mixture and two single agents,matrine and azadirachtin,were also compared.The reducing loss effect of matrine-azadirachtin mixture, matrine and azadirachtin with the minimum effective concentration were determined by mixing these agents with all the grain in the warehouse,and the duration for each agent was measured.The toxicity of matrine and azadirachtin alone on Sitophilus zeamais was evaluated with residual film method. The results showed that the LC50 of azadirachtin and matrine to Sitophilus zeamais were respectively 0.112mg/cm2 and0.167mg/cm2 in 72 hours, and respectively 0.074mg/cm2 and 0.141mg/cm2 in 96 hours.In the contact insecticide test with compounded matrine and azadirachtin,CTC of different ratios of matrine and azadirachtin mixture were all greater than80 in 72 hours. CTC of 9 compounds were all greater than 120 in 96 hours. When the ratio of matrine and azadirachtin mixture was 3:2, CTC to Sitophilus zeamais in 72 hours and 96 hours were respectively 125.28 and 154.85, which were greater than any other ratios. This result showed a strong synergism and the ratio 3:2 was determined to be the optimal ratio. When the compound with the optimal ratio(matrine: azadirachtin=3:2) was used to control 3 species of stored grain pests, the best control efficiency was demonstrated on Oryzaephilus surinamensis and this was followed by Sitophilus zeamais and Tribolium castaneum.In the test with matrine-azadirachtin, after 15 days of treatment with1.0mg/kg matrine-azadirachtin, the adjusted mortality rate of Tribolium castaneum and Sitophilus zeamais reached to 100% and 94%, respectively. Therefore, the minimum effective concentration of matrine-azadirachtin was determined to be1.0mg/kg.The control efficiency of 1.0ppm matrine-azadirachtin mixture was better than that of matrine and azadirachtin alone.In the test of matrine-azadirachtin duration, after 6-month treatment, the smallest losses caused by pests were, in order, matrine-azadirachtin, matrine,azadirachtin and the blank control.The reducing loss effect of matrine-azadirachtin was the best,and this was followed by matrine and azadirachtin.The duration of matrine-azadirachtin was longer than that of matrine and azadirachtin.