Reduced fertilization regimes could boost biocontrol service without reducing crop yield.

Agricultural intensification can disrupt trophic networks by altering interactions between plants, pests and their natural enemies. We investigated the effects of two fertilization levels (high vs. medium) on the performance of the parasitoid Aphidius ervi and the coccinellid predator Adalia bipunctata in controlling the aphid Macrosiphum euphorbiae on tomato plants. In a controlled greenhouse experiment, we measured aphid densities and plant growth in response to fertilization treatments, either alone or combined with one of the two natural enemies. We demonstrated that high-fertilization regime enhances plant growth and aphid population density, but reduces the efficiency of the parasitoid as biocontrol agent. In contrast, the predator A. bipunctata maintained stable performance regardless of fertilization regime. Therefore the impact of plant nutrition on biological control is species-specific. These findings highlight the importance of integrating fertilization management into pest control strategies. Excessive nutrient inputs may compromise the effectiveness of certain biological control agents by benefiting pests more than their natural enemies. Adjusting fertilization practices according to the natural enemy used could enhance pest suppression while supporting sustainable crop production.