| Compared with common pesticide formulations,microcapsules have many advantages such as prolong controlling effect, improve using efficiency, avoid decomposition and invalidation, abate toxicity and harmfulness, reduce environment pollution, and so on. Avermectins was the high efficiency biogenic pesticides and largely applied for controlling agricultural pests. However, avermectins have short field residual activity because of marked degradation effects, in addition, the main formulation of avermectins is EC, which consumed a lot of organic solvent, and resulted in environment pollution and resource waste, but avermectins microcapsules can avoid forenamed problems. So we have studied avermectins microcapsules with UF-resin via in-situ polymerization, obtained the optimal conditions of preparation system, and main contents is as the following aspects:1. For the screening the formaldehyde/ urea (F/U) mole ratio, the optimal F/U mole ratios were 1.75~2.0. There were higher activity and optimum separation pH of U-F pre-polymer prepared in above F/U mole ratio. The UF-resin which prepared with these pre-polymer had good toughness, the UF-resin particles were very minuteness and arranged compactly. Under these F/U mole ratio microcapsules showed excellent surface morphology and the product displayed high encapsulation efficiencies.2. For the screening the preparation system promoter of avermectins microcapsules, the optimal conditions were as follows: toluene and thlorobenzene at weight ratio of 3:4 as solvent, the dosage of dispersant LS was 1.5%, the dosage of silicone defoamer X-10C was 0.7%. Under these conditions, microcapsules showed satisfied surface morphology and particles size distribution, with the mean particle diameter of 4.07μm. The product displayed good stability and its encapsulation efficiencies were 98.89%. IR spectra showed that avermectins was contained in microcapsules.3. AVM CS had been prepared by added NP-10 Sodium Ligninsulfonate xanthan gum and ethylene glycol as promoter after in-situ polymerization reaction in aqueous medium. The quality specifications, including suspension rate and encapsulation rate were determined. All the results were up to standard. In additional, the encapsulation rate was above 98%, and suspension rate was above 86%. The changes of the encapsulation rate, content and suspension rate were determined after hot and cold storage. The rates of dehydration were determined too. After hot and cold storage, the encapsulation rate was still above 95%, suspension rate were above 80%, and the rates of dehydration were about 2%. The results showed that the specifications of AVM CS had no significant changes.4. The release rates of AVM CS and AVM TC were measured at methanol- PBS solution. The profile could be described by the first order kinetics equation, ln(100-Q)= - 0.1271t +4.7339,R2=0.9857, t50=9.5d(Q was accumulative release rate). The release t50 of AVM CS was about 3.4 times as much as AVM TC, AVM CS had obviously sustained effect.5. The control efficacies of AVM CS and AVM EC to Plutella xylostella L. D. destructor and tomato root knot nematode had been determined. Compared with AVM EC, the AVM CS showed lower initial efficacy to Plutella xylostella L. and D. destructor. It showed that active ingredient couldn't release completely from microcapsules at above two conditions. But the AVM CS showed more excellent efficacy longer residual activity and more safety than AVM EC when it was applied in soil to control tomato root knot nematode. Avermectins microcapsules could keep the active ingredient from decomposing or losing.6. The rapidly toxicity of AVM CS to Brachydanio rerio and Coturnix coturnix had been determined. The result showed that compared with AVM EC, the security of AVM CS to Brachydanio rerio and Coturnix coturnix was higher. Microcapsules could reduce the effect of pesticide to environment.
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