Invasive predator disrupts link between predator evenness and herbivore suppression

Biodiversity provided by non-crop plants has long been thought to strengthen conservation biological control providing food and habitat for natural enemies. More recently, greater evenness among enemies also suggested promote strong top-down control, but characteristics management strategies that or disrupt predators remain unclear. We examined effects of plants, the activity density invasive intraguild predator Pterostichus melanarius (Coleoptera: Carabidae), on crucifer flea beetle (Phyllotreta cruciferae; Coleoptera: Chrysomelidae). sampled ground-active predators, beetles, in-row coverage vegetation 52 Brassica fields across three US states, used structural equation models evaluate direct indirect, predator-mediated plant cover pest abundance. found high associated with higher indirectly lower herbivore densities, consistent stronger biocontrol. However, attracted invader P. melanarius. In turn, linked other while showing no effect suggesting potential disruptive interference While are widely known attract diverse it may be difficult growers manipulate communities increase enemy if commonly benefit from these resources as well. generally, our results suggest a need closer examination role predator-predator interactions in relationships between diversity agroecosystems.