Insect pest predation by arthropods and birds in different land use types with varying woody vegetation composition in agroecosystems of central Oromia, Ethiopia

Biological control by predators of insect pests is an important benefit of biodiversity, having a contribution to agricultural production. By preying on crop infesting insect pests, predatory arthropods and birds can provide an important ecosystem service. They support agricultural productivity, boosting crop yield and reducing demand for pesticides expense. Habitat quality of land use types, i.e., explained by vegetation cover, can impact the provision of ecosystem services thereby influencing the prevalence of the predators and their predation rates. In order to better understand the level of insect pest control service by predators, we conducted a field experiment to investigate levels of predation, using an attack on artificial caterpillars in response to land use types varied in vegetation cover. We found the attack rate by arthropods was more consistent across land use types than by birds, and the attack by birds was higher in modified land use types with sparse woody vegetation. Moreover, the attack rate for birds showed a decreasing tendency with increasing woody species richness, cover and stem density, while it showed less variation for arthropods. We conclude that biological control by birds is more effective in habitats with simplified vegetation cover than for arthropods in agricultural landscapes. Therefore, we recommend the prevalence of shade trees and small forest patches in agricultural landscapes for supporting the increased levels of insect pest control services provided by predatory birds and arthropods.

Automated summary

Biological control of insect pests by predators, such as predatory arthropods and birds, is an important ecosystem service that contributes to agricultural production. The habitat quality, specifically the vegetation cover, can influence the provision of this ecosystem service. In a field experiment, it was found that the attack rate by arthropods was consistent across different land use types, while the attack rate by birds was higher in modified land use types with sparse woody vegetation. Additionally, the attack rate for birds showed a decreasing trend with increasing woody species richness, cover, and stem density. This study suggests that shade trees and small forest patches should be promoted in agricultural landscapes to support increased levels of insect pest control services provided by predatory birds and arthropods.