Non-consumptive effects of Harmonia axyridis (Coleoptera: Coccinellidae) derived semiochemicals on Myzus persicae (Hemiptera: Aphididae).

Biological control agents are central to Integrated Pest Management, where they suppress herbivorous pests through direct consumption. However, natural enemies can exert non-consumptive effects (NCEs) on prey when predation risk is detected, altering behavior, physiology, or life-history traits in ways that reduce predation risk but impose fitness costs associated with anti-predator defense. Often, NCEs reduce pest pressure on plants via risk-induced changes in herbivore prey feeding, reproduction, and immigration/emigration. Predator-emitted odors are important risk cues, yet predator-derived semiochemicals remain underexplored as tools for pest management. Aphid prey detect predation risk of lady beetles by eavesdropping on their odor cues. However, the specific semiochemicals that signal predation risk have not been explored. Here, we investigated whether a synthesized blend containing key pyrazine semiochemicals produced by the multicolored Asian lady beetle, Harmonia axyridis (Pallas), can induce NCEs in the green peach aphid, Myzus persicae (Sulzer). In Y-tube olfactometer assays, both alate and apterous M. persicae preferred to orient toward plant odors rather than toward plants with the synthetic methoxypyrazine blend. Exposure to the synthetic methoxypyrazine blend reduced aphid fecundity in laboratory and greenhouse arenas but did not alter aphid survival or induce production of alate morphs. In the greenhouse experiment, aphid populations were 27% lower on plants exposed to the synthetic blend by day 14. These findings demonstrate that predator-derived semiochemicals can induce NCEs in aphids, suggesting a promising area of exploration for a semiochemical-based strategy for Integrated Pest Management.