Herbivore prevalence poorly predicts yield in diverse cropping systems

This is the authors' abstract. We don't add key points for this paper.

Industrialized agriculture needs sustainable alternatives to pesticides to avoid negative impacts on the environment and human health. Crop diversification is known to decrease pest pressure in agricultural crops. Up till now, the effects of insect herbivores on crop yield are often assumed to be equal among cropping systems. We sampled the insect community and yield of cabbages in five distinct cropping systems characterized by increasing crop diversity. Using structural equation modelling, we assessed how herbivorous insects influence cabbage yield through direct consumptive effects and indirect effects via changes in the insect community. The most diverse cropping system synergistically increased cabbage yield and herbivorous insect abundance and richness, whereas the other cropping systems did not differ consistently from each other. Cropping systems alter the effect that herbivores have on cabbage crop yield, where more herbivores do not necessarily lead to reduced yields. Specific insects had cropping system‐specific effects on yield, which reflect differences in the potential for distinct cropping systems to contribute to biological control of distinct herbivorous insects. In one of the cropping systems with cultivar mixtures, we observed negative impacts of herbivores on cabbage yield. This may result from a companioning cultivar drawing natural enemies away from the main cultivar, which would result in reduced biological control of herbivores on the main cultivar. Synthesis and applications. Our study shows that the design and characteristics of cropping systems should be considered when assessing insect herbivory effects on crop yield. As herbivorous insects have a smaller impact on yield in diverse cropping systems, crop diversification may synergize biodiversity conservation and food production.