The Field Trials of Some Biological Pesticides on Controlling Cnaphalocrocis medinalis

The efficacy of 5 biological insecticides against the lower instar larvae of Cnaphalocrocis medinalis were tested. The results showed that the control effects of veratridine 0.5% WP,rotenone 2.5% EC,abamectin 1.8% EC,Bacillus thuringiensis 2 000 IU/μL SC,Beauveria bassiana 4.0×1010 spores/g WP respectively at 3 000 g/ha,4 500 mL/ha,1200 mL/ha,6 000 mL/ha and 2 400 g/ha were between 90.30-94.60% in the seventh day after spraying the pesticides; and the effects of protective leaves were between 70.45-84.09% in the fifteenth day. Compared with chlorpyrifos 48% EC at 750 mL/ha,the differences of the control effects were not notable,but these biological insecticides took effect more slower than the chemical insecticide chlorpyrifos. When mixing the two pesticides respectively at a half of the recommended dose that was sprayed alone,the control efficacy were significantly more quick than those of the insecticides they were sprayed respectively,the control effects were between 84.00-92.96% in the third day,the effects of controlling larvae in the seventh day and protective leaves in the fifteenth day were similar or better than those of spraying the single insecticide respectively. So the 5 biological insecticides can substitute partly for chemical insecticides to control lower instar larvae of C. medinalis.