Combination of L-methionine and chlorantraniliprole enhances the abundance of opportunistic pathogenic bacteria in the intestine of greater wax moth leading to increased mortality risk

Abstract

Honey bees play an essential role in global crop production and agro-economic development due to their pollination properties. However, empirical evidence indicates a worldwide decline in bee colonies. The greater wax moth (GWM), a lepidopteran insect and natural enemy of honey bees, significantly contributes to this decline. Chlorantraniliprole (CH) is commonly used to control GWM in apiaries due to its efficacy and low toxicity to bees. However, long-term use of CH may lead to environmental pollution and GWM resistance. To enhance beekeeping safety and mitigate the risk of GWM resistance from prolonged CH use, we investigated the toxic effects of combining methionine (MET), which has demonstrated insecticidal activity against some lepidopteran pests, with CH on GWM. We conducted both individual and mixed exposure tests of MET and CH on GWM to finally evaluate the toxic effects of the combined treatment (MIX). The results indicated that the combination of MET and CH produced a synergistic lethal effect on GWM. Subsequent microbiome and immune-related gene expression assays, along with correlation analysis, revealed that the MIX treatment significantly reducing the abundance of Enterococcus spp., the primary genus in GWM, and induced immune stress in GWM. This phenomenon led to the proliferation of opportunistic pathogens such as Pseudomonas spp., ultimately leading to synergistic lethal effects on GWM mortality. This study provides new insights and data supporting the development of MET as a potential insecticide.