Green field margins as a strategy to promote the diversity of natural enemies of pests on rice cropping

Abstract

The increasing demand of environmentally-friendly produced food by society is motivating a change in the agricultural paradigm. The use of herbicides, although traditionally important for the control of weeds, may entail the loss of habitat for insect species that are potential allies of farmers, such as natural enemies of pests. To improve the diversity of natural enemies of pests, an alternative practice could be to avoid the use of herbicides in those areas where weeds do not compete directly with the crop, such as the field margins. To investigate this question, we evaluated how the presence of natural vegetation on rice field margins in the Ebro Delta affects the diversity (morphospecies richness) and abundance of arthropods that can potentially act as enemies of rice pests. We performed several arthropod samplings on rice margins with natural vegetation and rice margins with naked soil (herbicide treatments). Our results indicate that both the diversity and the abundance of arthropods was practically double in margins with natural vegetation (morphospecies richness: 35.3±2.1; abundance: 124±62) than in margins that had been treated with herbicides (21.0±9.6; 65±35). It is important to highlight that the chironomids group represents 84% ‘ of all the sampled arthropods when accounted for both types of margins. The rest of the arthropods detected do not pose a threat to rice cropping. On the contrary, most species can act as potential enemies of pests (e.g., syrphids, spiders, beetles or wasps among others). These results suggest that promoting green margins on rice fields can be a promising strategy for mitigating the loss of biodiversity while promoting biological control by natural enemies of pests.