From field to landscape: scaling-up the response of natural enemies and predation to methyl salicylate

In response to herbivory, plants emit herbivore-induced plant volatiles (HIPVs), many of which attract natural enemies of herbivores. One such HIPV, methyl salicylate (MeSA), has been deployed in agroecosystems to enhance biological control. However, the broader agroecosystem context-including field-level management and landscape complexity-can strongly influence natural enemy community dynamics. In this 2-yr study, we evaluated the interactive effects of MeSA, field-level practices (eg pesticide use and cultivar selection), and landscape complexity on natural enemy communities and their ecosystem services (eg predation) across 50 georeferenced sites on the 3 largest commercial cranberry farms in New Jersey (USA). At each site, we deployed 2 yellow sticky traps-1 baited with MeSA and 1 unbaited control-to monitor natural enemies and placed sentinel caterpillar egg masses to measure predation. Landscape metrics were quantified within 100, 250, 500, and 1500 m buffers. MeSA significantly increased the abundance and diversity of natural enemies, including 7 taxa. Field management practices also interacted with MeSA, with greater fungicide use associated with higher Syrphidae captures. Landscape features further modified MeSA effects across spatial scales; for example, a higher proportion of wetlands within 1500 m enhanced Empididae captures on MeSA-baited traps. However, MeSA and its interactions had no detectable effects on predation rates. Together, these findings demonstrate that the efficacy of HIPVs like MeSA in attracting natural enemies can be context dependent, underscoring the importance of integrating field management and landscape ecology into conservation biological control strategies in agroecosystems.