Increasing prey availability reduces early intraguild predation and improves biological control

Intraguild predation is an extreme form of competition, that depends on resource availability, niche overlap, behaviour and diversity. However, despite modelling and mesocosm experiments, field studies are scarce, and we know nothing of its temporal dynamics within real-world food webs, particularly in the context of biological control. To address this, we manipulated decomposer prey by adding manure to cereal fields, and analysed the diet of over 6000 predators over the entire cropping season during two years. Our results show that manure increased alternative prey, reduced intraguild predation and pest spreading in the first half of the season, without changing predator communities' diversity or evenness across treatments. We hypothesize the mechanism responsible for the observed effects are changes in predator behaviour. Our insights were possible due the high temporal resolution of our data, hence we recommend it as a way to address knowledge gaps in food webs, competition and biological control.