Prior Brassica rapa infestation by the cabbage bug, Eurydema ornata alters the performance and behavior of the peach-potato aphid, Myzus persicae and its natural enemies

BACKGROUND: Plant infestation by insect pests can alter plant physiology, thereby influencing the performance and behavior of subsequent herbivores and their natural enemies through indirect effects—changes in plant traits mediated by prior herbivory. This study investigates how prior infestation of Brassica rapa by the cabbage bug Eurydema ornata (Hemiptera: Pentatomidae) affects the aphid Myzus persicae (Hemiptera: Aphididae) and its natural enemies, the predator Harmonia axyridis Coleoptera: Coccinedllidae) and the parasitoid Aphidius gifuensis (Hymenoptera: Braconidae). To explore these interactions, we assessed aphid survival and fecundity, monitored population dynamics, examined the behavior of the predator and parasitoid, and analyzed plant volatile emissions. RESULTS: Our findings revealed a significant reduction in M. persicae fecundity on E. ornata infested plants. Additionally, aphids showed a significantly lower frequency of entering the olfactometer arm loaded with odors emitted from infested plants compared to those with odors from healthy plants. Both natural enemies, H. axyridis and A. gifuensis, demonstrated stronger attraction to infested plants in preference and foraging bioassays. Volatile analysis revealed higher emissions from infested plants, with significant increases in key compounds, such as 3-pentanol, (Z)-3-Hexenol, methyl isothiocyanate, dihydrojasmone, cis-Jasmone, D-Limonene, (E)-β-ocimene, β-Elemene, (E)-4,8–dimethyl–nonatriene and (E, E)-⍺-Farnesene. CONCLUSIONS: E. ornata infestation reduces the suitability of B. rapa for M. persicae and enhances the biocontrol potential of its natural enemies. These interactions highlight the importance of intra-guild competition and host manipulation in ecological, evolutionary and pest management perspectives.