Flower provision reduces intraguild predation between predators and increases aphid biocontrol in tomato

Intraguild predation (IGP)–the predation of a natural enemy species upon another one sharing a prey species–is relatively frequent in both natural and agroecosystems. This may reduce pest control and the establishment of predator populations during mass release of biological control agents or in multi-predator systems due to increased mortality of predators. IGP is exacerbated in isolated and space-limited systems such as greenhouses, due to reduced food resources and movement. Therefore, adding food resources as an alternative to the main prey, such as floral resources, could reduce IGP between natural enemies in these systems. In the present study we investigated the role of supplemental floral resources to help reduce intra- and interspecific IGP involving Harmonia axyridis and Propylea japonica (Coleoptera: Coccinellidae) in laboratory conditions, and we tested its application in a greenhouse setup. We found a significant reduction in intra- and interspecific IGP in laboratory conditions when floral resources were abundant. At a greenhouse scale, abundances of both ladybird species increased when floral resources were abundant, potentially through a combination of enhanced fertility and reduced IGP. This resulted in reduced abundances of aphid pest populations on tomato crops. Our study demonstrates that companion plants in greenhouses can improve pest control in systems with multi-species biological control agent releases.