The effect of Xenorhabdus bacteria metabolites on Colorado potato beetle (Leptinotarsa decemlineata) adult feeding and larval survival.

Colorado Potato Beetle (CPB) is one of the most destructive potato pests that can quickly develop resistance to insecticides. Therefore, new safe and effective control strategies that are less susceptible to the development of resistance by CPB are urgently needed. Due to their complex mode of action, the likelihood of resistance development by target pests is generally low with antifeedants. In the present study, we assessed the effect of secondary metabolites of various Xenorhabdus bacteria species and strains on CPB adult feeding and on larval development. The metabolites were applied in the form of cell free supernatants (CFSs) from Xenorhabdus cultures. In bioassay 1, leaves treated with ten Xenorhabdus cultures were fed to CPB adults, and their feeding was assessed daily for one week. In bioassay 2, CPB egg masses were placed on the leaves treated with five bacterial cultures, and larval development to pupae was monitored. Out of the ten Xenorhabdus cultures tested, two strains exhibited a significant reduction in the feeding behavior of Colorado Potato Beetle adults, with reductions of up to 70% compared to the control. The effect of CFSs on larval development was variable, and when treated with X. khoisanae SGI 197, over 90% of larvae died in the first few days before reaching the 2nd instar, and complete mortality was achieved on the 8th day of the experiment. Our study is the first study to demonstrate the antifeedant effect of Xenorhabdus cultures towards herbivorous beetles, and the metabolites of these bacteria may have potential for CPB control. Clearly, the metabolites produced by X. khoisanae SGI-197 may be a promising tool for CPB larvae control with the potential to significantly decrease damage to potato plants.

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Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.