Landscape structure influences natural pest suppression in a rice agroecosystem

Abstract

Agricultural landscapes are constantly changing as farmers adopt new production practices and respond to changing environmental conditions. Some of these changes alter landscape structure with impacts on natural pest control, pesticide use, and conservation of biodiversity. In rice agroecosystems the effect of landscape structure on natural enemies and pest suppression is often poorly understood. Here we investigate the effect of landscape composition and configuration on a key pest of rice, the brown planthopper (Nilaparvata lugens). Using N. lugens as sentinel prey coupled with predator exclusions, we investigated landscape effects on herbivore suppression and rice grain yield at multiple spatial scales in two regions of Bangladesh. Ladybird beetles and spiders were the most abundant natural enemies of N. lugens with landscape effects observed at all scales on ladybird beetles. Specifically, ladybird beetles were positively influenced by road edges, and fallow land, while spiders were strongly influenced only by rice phenology. Predator exclusion cages showed that N. lugens abundance significantly increased in caged plots, reducing rice gain yield. We also used an estimated biocontrol service index that showed a significant positive relationship with landscape diversity and a significant negative impact on pest density and yield loss. These results suggest that promoting fallow lands and fragmented patches between rice fields could lead to more sustainable insect pest management in rice agroecosystems, potentially reducing the practice of prophylactic insecticide use.

Predators control pests and increase yield across crop types and climates: a meta-analysis

“…This result also highlights that predators could reduce pest populations and increasing yield even in crop systems, which tend to be simpler environments than natural or semi-natural habitats and could lead to more strong species interactions ([67], but see for example enemies’ hypothesis: [68,69]). Although the influence of landscape context on biological control is outside the scope of our study, other possible explanations might be that landscape complexity at different scales is also important for biological control, and pest control in crops inserted in complex landscapes may benefit from additional resources [70,71]. Furthermore, to the best of our knowledge, our study is the first to suggest positive indirect effects of predators on crop yield across predator groups and crop types.…”