Abstract Plants produce volatile organic compounds (VOCs) in response to herbivory. Such signals mediate plant interactions with herbivores and their natural enemies. Different herbivores can elicit distinct responses in plants, influencing predator attraction. While invertebrate predators primarily rely on chemical cues, birds often use visual cues in addition to olfactory signals. We conducted a field experiment on two abundant willow species, Salix cinerea and Salix fragilis , to test whether herbivore‐specific elicitors induce changes in VOC emissions and if these changes affect predation rates. Treatments included insect‐derived extracts from beetles and caterpillars, and mechanical damage. We measured VOC emissions, leaf reflectance, and predator attack rates on plasticine caterpillar models. We detected 22 VOCs in total. Out of these, all were detected in S. fragilis and 19 in S. cinerea. We found species‐specific responses and predator interactions: In S. fragilis , treatments induced distinct VOC blends and individual compounds, such as ( E )‐β‐farnesene, which correlated with invertebrate predation. In S. cinerea , treatment‐specific effects were limited to individual VOCs, while variation in background VOCs influenced bird predation. In S. cinerea, leaf reflectance did not significantly vary with treatments but correlated with bird predation. Our findings highlight that specificity in plant responses to herbivory translates into differences in predator attraction under natural field conditions. We show that closely related plant species with contrasting defence strategies route top‐down control through different predator guilds, where inducible VOCs in S. fragilis recruit invertebrate predators, while constitutive chemical and visual traits in S. cinerea attract birds. Our findings provide a mechanistic explanation for variation among previous reports on VOC‐mediated predator attraction and show that some plant species rely on herbivore‐specific induction to attract predators of their herbivores while others employ alternative or constitutive defence cues. Read the free Plain Language Summary for this article on the Journal blog.
Mezzomo et al. (Tue,) studied this question.