Local species‐specific effect of trees and shrubs on the incidence of the millet head miner, <i>Heliocheilus albipunctella</i> (Lepidoptera, Noctuidae)

Abstract Understanding the interactions between crop pests, natural enemies and semi‐natural habitats in agricultural landscapes is crucial for developing ecology‐based pest management in agroecosystems. In the present study, we investigated the local‐scale species‐specific effect of tree and shrub cover and diversity on the incidence and natural pest regulation of the millet head miner (MHM), Heliocheilus albipunctella (Lepidoptera: Noctuidae) de Joannis and subsequent grain losses in a tree‐crop agroforestry system in Senegal. To this purpose, we monitored a network of 60 millet fields with variable tree and shrub species composition within a 50‐m radius buffer around the centre of millet fields. The proportion of egg‐infested panicles increased with the area covered by baobabs ( Adansonia digitata ) but decreased with that of soapberry trees ( Balanites aegyptiaca ). Baobabs and apple‐ring acacias ( Faidherbia albida ) locally increased pest incidence and associated grain loss, likely by providing favourable microhabitats for MHM and limiting the impact of larval parasitoids, respectively. In contrast, bushwillow shrubs ( Combretum micranthum ) increased egg parasitism, but not enough to disrupt the relationships between crop colonization, pest incidence and yield loss. Furthermore, Shannon's diversity index had no measurable influence on pest dynamics, suggesting that species identity and functional traits are more important than diversity per se. These findings underline the importance of careful selection of tree and shrub species in agroforestry design strategies for optimizing the delivery of multiple ecosystem services. Integrating tree functional traits, seasonal canopy dynamics and spatial scale considerations is key to enhancing ecosystem services such as biological control in tree‐crop agroforestry systems.