How Much, How Long and When: Density, Duration and Plant Stage Affect Herbivore-induced Plant Volatiles in Maize by the Corn Leafhopper.

Although sessile, plants have sophisticated systems of perceiving their environment. They respond to biotic and abiotic stress, for instance, they can detect damage caused by insect feeding or oviposition and respond by releasing volatile compounds, known as herbivore- or oviposition-induced plant volatiles (HIPVs or OIPVs). The corn leafhopper, Dalbulus maidis (DeLong and Wolcott), is a sap-sucking insect that has been causing challenges to maize growers across the Americas by transmitting phytopathogens that cause substantial production losses. In this study, we evaluated whether maize plants modify their volatile emissions in response to different densities of pathogen-free D. maidis adults, the type of injury, and varying injury durations at two distinct vegetative stages. The results showed that injury caused by corn leafhoppers induced the release of HIPVs and OIPVs, with the response influenced by the plant stage, insect density, type of injury and injury duration. Density primarily affected the quantity of volatile induction, injury duration shaped the induced blend, and plant stage influenced all these aspects. Consistently induced compounds by all the factors tested included (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), (E)-β-caryophyllene, and (E)-β-farnesene. Whereas the oviposition injury induced only two volatiles: nonanal and decanal. This study highlights how maize respond with different blend profile of HIPVs and OIPVs, demonstrating that maize adapts its volatile emissions depending on the intensity of stress it has been submitted. These findings can be further explored in multitrophic interactions, potentially influencing natural enemies that utilize these volatiles as cues in the environment.