Development Of 20% Chlorpyrifos Micro-emulsion With Chenopodium Ambrosioides Essential Oil As Auxiliary

Chlorpyrifos is a broad spectrum, moderately toxic organophosphate insecticide. Eemulsifiable concentrate and granule are dominant formulation of chlorpyrifos, which contain organic solvents with potential environmental pollution. Chenopodium ambrosioides, originally from South America, is an annual plant with a strong aromatic odor and is widely distributed in the subtropical and tropical zone as well as in temperate regions. The plant have become a harmful weed invading agricultural field in some regions. The essential oil of C. ambrosioides was proposed as a pesticide adjuvant in this study. Based on the screening for solvent and emulsifier, and the evaluation for the formulation stability under the stress of exteme temperatures, 20% chlorpyrifos EC was developed. Then the toxicity of 20% chlorpyrifos on the larvae of diamondback moth (DBM), Plutella xylostella was investigated,as well as the effect of 20% chlorpyrifos on the DBM enzyme related with pesticide resistance. Field test of 20% chlorpyrifos against DBM were also conducted to evaluate the filed effect.(1) Based on leaf-dip bioassay, the best proportion between C. ambrosioides and chlorpyrifos was screened out. According the result of stability experiment, DMF and DMF+cyclohexanone were selected as solvent and 0201B,0206B as emulsifier. The chlorpyrifos ME contained chlorpyrifos (20%), DMF (10%), glycerol (5%), 0206B (20%) and water (45%).(2) Stability under extreme temperatures of chlorpyrifos ME was carried on at 0±2℃for seven days. There were no obvious separated granule and oil components. With the treatment of high temperature at 54±2℃for 14 days, the relative decomposition rate of chlorpyrifos was 3.57% and all other index was eligible.(3) LD50 of chlorpyrifos ME prescription A and B against DBM were 0.8235 and 0.6995 fold, respectively, when compared with 40% chlorpyrifos EC.(4) Biochemistry analysis showed that C. ambrosioides essential oil could enhance the inhibition of chlorpyrifos to AChE , CarE and GSTs activities of P. xylostella larvae.(5) Field test against DBM showed that 20% chlorpyrifos ME could achieve a higher control effect than 40% chlorpyrifos EC.