Degradation Rule and Control Effect of Commonly Used Pesticides in Tobacco in Henan
[Objective]The degradation law and control effect of pesticides commonly used in tobacco production in Henan Province were investigated,so as to provide reference for rational application to reduce the risk of excessive pesticide residues in tobacco leaves.[Method]The residues and control effects of 4 kinds of neonicotinoid insecticides(acetamiprid,imidacloprild,thiamethoxam,pymetrozine),4 kinds of pyrethroid insecticides(lambda-cyhalothrin,cypermethrin,daltamethrin,fenvalerate)and 4 kinds of fungicides(oxadixyl,propamocarb,metalaxyl,dimethomorph)commonly used in tobacco production in Henan were studied.[Result]There was no significant difference in the control effect of the 4 neo-nicotinic insecticides on aphids.Imidacloprid degraded fastest and the residual fell below the safety limit published by CORESTA in seven days after application.The residual of thiamethoxam fell below the safety limit in 14 days after application.The residue levels of all tested insecticides in cured tobacco leaves samples were lower than the safety limits.Among all the pyrethroid insecticides been tested,deltamethrin had the highest degradation rate(which fell below the safety limit in 21 days after application)and the lowest residue.The effect of fenvalerate on controlling Helicoverpa assulta was significantly higher than that of the others,followed by deltamethrin.There was no significant difference in the control effect of the 4 fungicides on tobacco black shank,among which the degradation of oxadixyl was slow,and the residue of cured tobacco leaves was beyond the safety limit,indicating that it mustn't be used.[Conclusion]All pesticides have obvious control effect.Different pesticides have different absorption characteristics and degradation rules,and these characteristics should be comprehensively considered in production to reduce the risk of excessive pesticide residue.
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