Herbivore prevalence poorly predicts yield in diverse cropping systems

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, effects of insect herbivores on crop yield are often assumed equal among cropping systems. Here, we show that cropping system alters the effect that herbivores have on cabbage crop yield, where more herbivores do not necessarily lead to reduced yields. Our most diverse cropping system had simultaneously the highest number of herbivores and highest crop yield. Conversely, in a cultivar mixture we observed negative impacts of herbivores on yield. Our study shows that, in addition to the time of arrival and type of herbivore, cropping system should be considered when assessing how insect herbivores affect crop yield. We emphasize how our perception of herbivorous insects as pests is flawed and limits conservation efforts and sustainable farming practices.