Non-crop habitats concurrently drive crop colonization by the millet head miner and regulation by natural enemies

Sow Ahmadou, Soti Valérie, Thiaw Ibrahima, Brévault Thierry. 2022. Non-crop habitats concurrently drive crop colonization by the millet head miner and regulation by natural enemies. Basic and Applied Ecology, 64 : 45-56.

Résumé : Non-crop habitats, depending on their composition, can enhance the abundance and diversity of natural enemies of crop pests, but also at the same time provide resources to pests, thereby reducing the effect on pest incidence and resulting yield losses. The objective of the present study was to test (1) the effect of semi-natural habitats in the landscape on crop colonization by pests and natural regulation, and (2) the relationship between natural regulation and pest incidence. The pearl millet head miner (MHM) was selected as a case study because it is a key pest of millet cultivated in traditional pesticide-free tree-crop agroforestry systems in which its control mostly relies on the action of natural enemies. A set of 24 millet fields were selected in a 20×20 km area in Senegal, from the analysis of high-resolution satellite images (Pléiades), and hypotheses on the relative abundance of semi-natural habitats (here trees and rangelands) in the agricultural landscape. Millet fields were monitored for pest infestation of panicles and pest natural regulation. We used partial least squares structural equation modelling (PLS-PM) to evaluate the relationships between the abundance and diversity of semi-natural habitats at the landscape scale, crop colonization, natural pest regulation, and pest incidence. Panicle colonization by the MHM was generally high (14–92%) and increased with the abundance of trees and to a lesser extent with the rangeland area at a 1000 m-radius around millet fields. However, regulation provided by natural enemies was amplified by the abundance of trees at a local scale (250 m-radius around millet fields). This was particularly true at early crop colonization of the MHM with parasitism and direct predation on eggs and young larvae. This multi-scale effect of semi-natural habitats on crop colonization and natural regulation could explain why no clear relationship between crop colonization and pest incidence, nor natural regulation and pest incidence, was observed. Future studies on the identification of complex species-specific interactions between trees and natural enemies should provide a better understanding of the ecological processes underlying the performance of natural regulation of MHM populations.

Mots-clés Agrovoc : gestion des organismes nuisibles, ennemi naturel, ravageur des plantes, Cenchrus americanus

Mots-clés géographiques Agrovoc : Sénégal

Mots-clés complémentaires : Heliocheilus albipunctella

Mots-clés libres : Conservation biological control, Natural regulation, Millet-based agroecosystem, Landscape composition, Pest management, Tropical semi-arid environment

Classification Agris : H10 - Ravageurs des plantes
H01 - Protection des végétaux - Considérations générales

Champ stratégique Cirad : CTS 4 (2019-) - Santé des plantes, des animaux et des écosystèmes

Agences de financement hors UE : Consortium of International Agricultural Research Centers

Programme de financement européen : FP3

Auteurs et affiliations

• Sow Ahmadou, CIRAD-PERSYST-UPR AIDA (FRA) ORCID: 0000-0001-8987-4828 - auteur correspondant
• Soti Valérie, CIRAD-PERSYST-UPR AIDA (REU)
• Thiaw Ibrahima, CSE [Centre de suivi écologique] (SEN)
• Brévault Thierry, CIRAD-PERSYST-UPR AIDA (SEN) ORCID: 0000-0003-0159-3509

Source : Cirad-Agritrop (https://agritrop.cirad.fr/603371/)

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