Balance the rapid release of insecticide microcapsules using double-layer shielding effect when the foliar application

The development of microencapsulation is currently blocked by the mismatch between the release rate and pest-control demand in terms of improving the photostability of pesticides. Achieving both long-term stability and quick release of pesticides through the use of microcapsules (MCs) is an effective way to increase pesticide efficiency. Sodium lignosulfonate and four types of polyalkyl quaternary ammonium salts (PQAS) were used as shell materials in the fabrication of four types of microcapsules by electrostatic self-assembly. The effects of the PQAS alkyl chain length on the morphology, zeta potential, molecular electrostatic potential, particle size distribution, encapsulation efficiency, release behaviour, anti-photolysis performance, and field application effects of the MCs were investigated. The four types of MCs were spherical and 0.5–3 μm in size, and they had an encapsulation efficiency of more than 75 %. The X-ray diffraction results showed that the longer the alkyl chain of PQAS was, the looser the material formed by electrostatic attraction was. With the increase of the alkyl chain length of PQAS, the MCs shell was looser and easier to deform, leading to rapid nuclear release. Therefore, the MCs shells were looser and more prone to deformation with increasing PQAS alkyl chain length, resulting in the quick release of the core. This quick release of the core to the bottom of the microcapsules and the loose shell formed a double-layer structure, which effectively prevented ultraviolet degradation. Therefore, abamectin MCs with quick-release and favourable anti-photolysis performances showed advantages in controlling Plutella. xylostella and Pieris. rapae insect pests. Octadecyl dimethyl benzyl ammonium chloride can be used to fabricate loose MCs by electrostatic self-assembly, which achieves both rapid and long-term pest control.