New primary resource increases predation on a pest in a banana agroecosystem |
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Authors: | Gregory Mollot Philippe Tixier Françoise Lescourret Serge Quilici Pierre‐François Duyck |
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Affiliation: | 1. CIRAD, UR 26 Systèmes de culture à base de bananiers, plantains et ananas, PRAM CIRAD Petit Morne, BP 214, 97285 Le Lamentin cedex 2, Martinique, France;2. INRA, UR1115 Plantes et Systèmes de Culture Horticoles, Domaine St Paul, Site Agroparc, F‐84914 Avignon Cedex 9, France;3. CIRAD, UMR 53 Peuplements Végétaux et Bioagresseurs en Milieu Tropical Cirad/Université de La Réunion, 7 chemin de l’IRAT, 97410 St‐Pierre, La Réunion, France |
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Abstract: | - 1 Primary resources may affect the structure of species assemblages in upper trophic levels of food webs. These bottom‐up effects may involve important ecological processes that affect pest control. For example, population densities of natural enemies may increase when alternative preys are favoured by a new resource.
- 2 Ants, particularly Solenopsis geminata Forel (Myrmicinae), are recognized as effective predators of herbivores eggs. In the present study, we tested the hypothesis that the addition of a primary resource in a banana agroecosystem will increase pest control of the banana weevil Cosmopolites sordidus Germar (Coleoptera, Curculionidae) by ants.
- 3 Using stable isotope analyses, we showed that S. geminata used the new resource pathway provided by the addition of a cover crop. This change was revealed by increased δ13C values (13C/12C) in a cover crop treatment (C4 plant) compared with a banana (C3 plant) in bare soil treatment.
- 4 We also showed that the abundance of S. geminata, as measured with pitfall traps, was 4.8–5.4‐fold higher in the cover crop treatment than in the bare soil treatment. Estimation of egg predation rates was in the range 7.8–70.3%, which occurred in plots with the lowest and highest S. geminata numbers, respectively.
- 5 The addition of a new primary resource in this system changed the origin of the carbon consumed by predators and increased their densities. The increased ant abundance resulted in increased predation of weevil eggs, which was consistent with our hypothesis. These results will be useful for the design of cropping systems that enhance the biological regulation of pests.
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Keywords: | Apparent competition Cosmopolites sordidus cover crop diet Musa spp. predation rate Solenopsis geminata stable isotope |
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