Optimized nanopesticide delivery of thiamethoxam to cowpeas (Vigna unguiculata) controls thrips (Megalurothrips usitatus) and reduces toxicity to non-target worker bees (Apis mellifera)

Abstract

Thrips [Megalurothrips usitatus (Bagnall)] (Thysanoptera: Thripidae) is a pest that poses a serious challenge to global crop production and food supply, especially to the cowpea industry. Nano-delivery systems have broad application prospects in the prevention and control of pests in agriculture. Herein, three types of amino acid (AA) modified polysuccinimide nano-delivery carriers (PSI-GABA, PSI-ASP and PSI-GLU) were constructed with a diameter of approximately 150 nm to load thiamethoxam (THX), which enhanced THX effective distribution and use with cowpea plants. Significantly, the PSI-GLU nanocarrier effectively delivered THX to cowpea plant tissues following 6 h of soil application. Compared with commercial THX suspension (SC), the THX content in the leaves of cowpea plants was increased by 2.3 times. Confocal laser scanning microscopy revealed that the FITC-labeled PSI-GLU nanocarrier reached the leaves through the vascular system after being absorbed by the roots of cowpea plants. The PSI-GLU nanocarrier decreased the LC50 of THX from 11.45 to 7.79 mg/L and significantly enhanced the insecticidal effect. The PSI-GLU nanocarrier also improved the safety of THX to worker bees at 48 h, and moreover showed a growth-promoting effect on cowpea seedlings. These results demonstrated that the PSI-GLU nano-delivery carrier has promising uses on improving the effective utilization of THX for the sustainable control of thrips and reducing the risk to non-target pollutions.