Study on the preparation of sustained-release thiamethoxam microspheres by blending microcrystalline wax with tapioca starch ester or dehydroabietic acid ester as the matrix

Abstract The controlled release formulations (CRFs) are considered an effective way to solve damage to the environment caused by traditional pesticide formulations. To change the defects of traditional neonicotinoid formulations that dissolve quickly in soil, three types of thiamethoxam (TM) CRFs microspheres with content of 20% TM were prepared using microcrystalline wax (MK) as the matrix, laurate acid tapioca starch ester (MSK) and stearyl dehydroabietic acid ester (MDK) as the regulators of ingredient release. The release behavior of CRFs microspheres in water and soil showed that the microspheres had superior stability and different TM sustained-release periods, and TM release of the microspheres in soil was faster than that in water. The release rate is TM/MDK > TM/MSK > TM/MK. In water, the release of thiamethoxam technical was finished after 38 hours. However, for TM/MK, the release rate was 94% after 240 hours, and the release time was extended by 6 times. Meanwhile, TM/MDK has a particular pH-responsive release. Research shows that using microcrystalline wax as the matrix, by adding MSK or MDK to adjust the release of ingredients, pesticide CRFs microspheres with different release periods can be prepared to achieve the purpose of controlling the release of pesticides.