Birds and bats contribute to natural regulation of the millet head miner in tree-crop agroforestry systems

Ahmadou Sow (1) , Djiby Seye (1) , Emile Faye (2, 3) , Laure Benoit (4, 5) , Maxime Galan (4) , Julien Haran (4) , Thierry Brévault (6, 2, 7)

1 UCAD - Université Cheikh Anta Diop de Dakar [Sénégal]
2 ISRA - Institut Sénégalais de Recherches Agricoles [Dakar]
3 UPR HORTSYS - Fonctionnement agroécologique et performances des systèmes de cultures horticoles
4 UMR CBGP - Centre de Biologie pour la Gestion des Populations
5 Cirad-BIOS - Département Systèmes Biologiques
6 UPR AIDA - Agroécologie et Intensification Durables des cultures annuelles
7 Cirad-PERSYST - Département Performances des systèmes de production et de transformation tropicaux

A better understanding of environmental factors driving natural pest regulation is a major challenge for designing sustainable cropping systems. The objective of the present study was to assess the association between vegetation openness in traditional tree-crop agroforestry systems in Senegal, richness and abundance of vertebrates including insectivorous birds and bats, and their contribution to the natural regulation of crop pests. The millet head miner (MHM), Heliocheilus albipunctella (Lepidoptera, Noctuidae), a major constraint to increasing millet crop productivity in sub-Saharan Africa, was selected as a model system. Ten sites separated by at least one km from each other were selected in a 100 km2 study area in the Peanut basin in Senegal. In each site, a pair of millet fields distant from at least 100 m each was selected according to a gradient of vegetation openness within a 100-m radius buffer with sampling plot (5 × 5 m) at the center. Nine insectivorous bird and bat species were recorded in millet fields over the 2017 cropping season and their predator status was confirmed by direct observation or DNA detection in fecal samples. Grain losses were reduced when panicles were accessible to birds and bats, confirming their net contribution to pest regulation. At a local scale, tree diversity and vegetation openness were important predictors of the abundance of insectivorous village weaver birds and grey-headed sparrows, respectively. Some tree species (soapberry trees and neems) indirectly contributed to natural regulation of the MHM likely by providing refuges to insectivorous vertebrates whereas other tree species (baobabs) provided disservices as possible refuges for the MHM moths. Further research is needed to better understand relationships between tree cover, food web interactions and natural pest suppression, so that specific conservation measures such as habitat management can be designed to improve pest control.

Mots clés: Trophic web; Biodiversity; Pest management; Tree cover; Ecosystem services; Agroecology; Conservation biological control; Bats Birds

Domaines: Sciences du Vivant [q-bio]; Biologie animale

Ahmadou Sow, Djiby Seye, Emile Faye, Laure Benoit, Maxime Galan, et al.. Birds and bats contribute to natural regulation of the millet head miner in tree-crop agroforestry systems. Crop Protection, 2020, 132, pp.105127. ⟨10.1016/j.cropro.2020.105127⟩. ⟨hal-02558065⟩