Within-field crop diversity and landscape complexity decrease the abundance of fall armyworm larvae in maize cropping systems

Abstract

The composition and spatial arrangement of multiple crop and non-crop habitats at a field and landscape levels have the potential to modify the abundance and structure of arthropod communities. In particular, semi-natural habitats can provide important life support functions to a range of natural enemies of agricultural pests. How such traits might affect generalist predators has poorly been considered in complex landscapes dominated by intercropping and trees within a mosaic of small-scale agricultural plots in Africa. The objective of the present study was to test the hypothesis that crop diversity and landscape complexity in maize cropping systems decrease the abundance of crop pests through natural regulation by generalist predators. For this purpose, we monitored the fall armyworm abundance and predation of sentinel larvae by predatory ants across a set of maize fields with contrasted within-field crop diversity and abundance of semi-natural vegetation including trees and shrubs in their surrounding landscape. A negative effect of crop diversity and landscape complexity on FAW abundance, and a species-specific effect on ant abundance, were observed. However, no significant effect of ant abundance or predation on FAW abundance was observed, suggesting that habitat complexity by itself or other natural enemy communities such as parasitoids could play a complementary role to explain FAW abundance in maize crops.