| The mixture of ?-cyhalothrin and emamectin benzoate is very synergistic against many kinds of pest.There are very few products containing both pesticides in the market.These products are emulsifiable concentrate,emulsion and micro-emulsion,which are bad for environment because containing much organic solvent.The problem of drug's degradation isn't relved.The microspheres containing ?-cyhalothrin and emamectin benzoate was studied with the method of emulsion solvent evaporation based on ?-cyhalothrin and emamectin benzoate as core materials that were mixed in certain proportion and polylactic acid as wall materials which is a kind of biodegradable high-molecular polymer.The optimum prescription and preparation conditions were obtained by studying some major factors.The microspheres were processed into the 5%?-cyhalothrin-emamectin benzoate microspheres suspension concentrate(5%CEM SC)and the relative optimum kinds and amount of wetting agents,dispersants,thickening agents and antifreezing agents were obtained.The toxicity and synergism of 5%CEM SC against the larva of Plutella xylostella was evaluated using the method of leaf diping.1 Study on the prescription and preparation conditions of ?-cyhalothrin-emamectin benzoate microspheresThe factors,such as types and amount of emulsifier,mass ratio of core material to wall material,concentration of PLA,volume ratio of oil phase to water phase,emulsifying speed,emulsifying time and stirring speed,were studied during the preparation of ?-cyhalothrin-emamectin benzoate microspheres.After pesticides loading,entrapment rate,mean diameter,span of microspheres were evaluated,the optimum prescription and preparation conditions were obtained.the optimum prescription and preparation conditions was that emulsifier type was gelatin plus arab glue(the mass rate was 1:1);content(m/v)of emulsifier was 1.5%;mass ratio of core material to wall material was 1:3;content of PLA was 90 mg/mL;volume ratio of oil phase to water phase wasl:10;emulsifying speed was 8000 r/min;emulsifying time was 0.8 min;stirring speed was 700 r/min.the microspheres prepared with the above conditions was smooth and spherical,whose pesticides loading,entrapment rate,mean diameter and span were 22.94±0.09%,95.63±0.39%,8.84±0.17?m,1.11±0.02?respectively.The result of differential scanning calorimetry(DSC)indicated that core materials were combine with wall materials formed via chemical bonds.Releasing of the pesticides conformed to first order kinetics equation and the microspheres had good release property.2 Preparation of 5%CEM SCThe relative optimum prescription was obtained through screening of wetting agents,dispersants,thickening agents and antifreezing agents.The relative optimum prescription was that the microspheres changed about 21.80g;wetting agent was Morwet EFW charging 2%;dispersant was Morwet D-425 charging 5%;thickening agent was Magnesium aluminum silicate charging 2%;antifreezing agent was ethylene glycol charging 5%;organic silicon defoamer charged 0.1%;water was added to 100%.The suspensibility,moisture extraction rate and persistent foaming of the suspension concentrate prepared with the above conditions was 85.6±0.4%,5.2±0.3%and 26mL respectively.The suspension concentrate possessed good dispersity and liquidity.3 The test for indoor toxicity and synergism against the larva of Plutella xylostella of 5%CEM SCThe result was obtained by leaf diping method that the LC50 of ?-cyhalothrin,emamectin benzoate and 5%CEM SC against the larva of Plutella xylostella were 207.3 mg/L,12.8 mg/L,28.7mg/L respectively.The co-toxicity coefficient(CTC)of 5%CEM SC was 204.47,which indicated that 5%CEM SC had prominent synergism.The long-last toxicity of 5%CEM SC was distinctly superior to commercial formulation. |
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