The Effect of Ice-Nucleation-Active Bacteria on Metabolic Regulation in Evergestis extimalis (Scopoli) (Lepidoptera: Pyralidae) Overwintering Larvae on the Qinghai-Tibet Plateau

SIMPLE SUMMARY: Evergestis extimalis (Scopoli) causes a serious reduction in the yield of spring oilseed rape every year. Until now, using chemosynthesis pesticides has been the main strategy to control E. extimalis. Biopesticide, as an alternative treatment, has attracted widely attention as it has little effect on the natural enemy and a low potential for promoting resistance. Our results have indicated that ice-nucleation-active microbes were able to stimulate trehalase activity, thereby leading to the reduction of trehalose accumulation. Consequently, E. extimalis showed an obviously decreased survival rate and ability to withstand low temperatures in the Qinghai-Tibet Plateau. Therefore, the use of INA bacteria has the potential to become a new strategy for the biological control of pests. ABSTRACT: Evergestis extimalis (Scopoli) is a significant pest of spring oilseed rape in the Qinghai-Tibet Plateau. It has developed resistance to many commonly used insecticides. Therefore, biopesticides should be used to replace the chemical pesticides in pest control. In this study, the effects of ice-nucleation-active (INA) microbes (Pseudomonas syringae 1.7277, P. syringae 1.3200, and Erwinia pyrifoliae 1.3333) on E. extimalis were evaluated. The supercooling points (SCP) were markedly increased due to the INA bacteria application when they were compared to those of the untreated samples. Specifically, the SCP of E. extimalis after its exposure to a high concentration of INA bacteria in February were −10.72 °C, −13.73 °C, and −14.04 °C. Our findings have demonstrated that the trehalase (Tre) genes were up-regulated by the application of the INA bacteria, thereby resulting in an increased trehalase activity. Overall, the INA bacteria could act as effective heterogeneous ice nuclei which could lower the hardiness of E. extimalis to the cold and then freeze them to death in an extremely cold winter. Therefore, the control of insect pests with INA bacteria goes without doubt, in theory.