Screening of biogenic pesticides to Diorhbda tarsalis and effects of biogenic pesticides to bio-diversity
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Key Words：Diorhbda tarsalis, biogenic pesticides, determining toxity, field efficacy, biodiversity
Abstract： In order to screen pesticides against Diorhbda tarsalis Weise, toxicity of the pesticides was assayed by indoor and field experiments. The results of indoor toxicity showed that the sensitivity of D. tarsalis to vertrine 0.5% (SL) is the highest; the LD50 value is 0.139 mg/L, the followings are azadirachtin 0.3% (EC), L2, matrine 1% (SL), and L1; the LD50 values of these pesticides are 0.457, 1352, 2.014 and 2.251 mg/L respectively. Those are all higher than that of other biogenic pesticides and chemical pesticides. The results of field efficacy showed 100% control effect of vertrine against D. tarsalis in 21 days, while the effect of matrine and azadirachtin are both 86.67%. The control effect of L2 and L1 are only 66.67% and 40％, respectively. In addition, above pesticides has distinct control effects to nontarget pest Empoasca spp. as well. Those control effects in 21 days, except for L1, are all higher than 68.89％. Azadirachtin, matrine, L2, and L1 are safe to narural enemies Hippodamia variegate and Chrysopa sinica; the highest correction reduced rate is 57.14％. What is more, these pesticides has minor effect on biodiversity in ecosystem. The average biodiversity index of matrine in all time is 2.93, that of azadirachtin, L1, L2, and vertrine is 2.88, 2.45, 2.43, and 2.07, respectively. Therefore, azadirachtin and matrine are considered to be ideal pesticides to control D. tarsalis.