Release-controlled microcapsules of thiamethoxam encapsulated in beeswax and their application in field
Abstract Using beeswax as wrapping matrix, two types of release-controlled TM (thiamethoxam)/BK(beeswax-kaolin) microcapsules were prepared by adsorbing TM on kaolin and then encapsulated with beeswax, or directly wrapping TM with beeswax. The structure and morphology of the TM/BK microcapsules were characterized. The effects of different preparation methods, the particle size, pH conditions and different additives on the release property of the TM/BK microcapsules were investigated in water and soil column to compare the advantages of the two approaches. Finally, the insecticidal effect of the TM/BK microcapsules against sugarcane borer and rice planthopper was tested. The results show that the TM/BK microcapsules have a better sustained-release in both water and soil, and the release rate is different under different pH conditions. In addition, the releasing time of the TM/BK microcapsules can be modified by different preparation methods and combination of different additives. In the field applications, the insecticidal activity of the TM/BK microcapsules was better than that of non-sustained control group. Especially in the rice field test, 45 days after the application, the control group lost the activity against rice planthopper because of drug loss, whereas the TM/BK microcapsule group still retained about 90% of the insecticidal activity. The results suggest that the microcapsules have better agricultural application for insect control.