Shared semiochemicals in a tri-trophic system benefit crop plants

Prey commonly use volatile chemicals released from predators to infer the level of danger and can enact phenotypic changes to increase their chance of survival. Because some predators emit volatiles that are also used in plant defense signaling, there is the potential for plants to also respond to predator cues. In the Colorado potato beetle, Leptinotarsa decemlineata, predator spined soldier bug, Podisus maculiventris, potato, Solanum tuberosum, system, the beetle responds to the predator aggregation semiochemical, which is comprised of predator-specific compounds and compounds that are known to be used by plants as green leaf volatile signals to induce their own defenses. Given this shared sensory cue in the system we asked the question; is the effect of the predator semiochemical on prey driven by the full predator semiochemical, or are there bioactive compounds in the blend that are also shared with the plants that are responsible for the prey behavioral changes? By fractionating the semiochemical into three treatments (full blend, shared cues, and predator only) and dispensing it in a replicated potato field with free-ranging herbivores, we found that the cues shared with the plant reduced herbivore feeding by 37 percent and the full blend by 41 percent compared to the control or predator specific fraction. Potato plants also responded to the shared cues by growing larger over the season and initiating flowering earlier, indicating that prey responses to the semiochemical could be direct or mediated by the plant’s response to the semiochemical. These findings highlight the potential utility of using shared cues for management purposes. Rather than using a semiochemical treatment that has a single target audience (i.e., the pest), we showed that a cue shared across multiple trophic levels decreased plant damage and increased growth, while eliciting anti-predation behavior in the prey.