Mémoire
| Résumé : | Generalist and dominant predators can ultimately have positive and negative outcomes for biological control. Intraguild predation or exploitative competition for resources are common drawbacks, whilst positive associations can show additive or synergistic effects that enhance pest regulation by an assemblage of species. Understanding this balance is therefore a prerequisite before recommending a taxon in a pest-management strategy.In Sub-Saharan Africa, the arboreal weaver ant (Oecophylla longinoda Latreille) mitigates the damage done by various pests in multiple production systems. However, little is known on how these dominant ants interact with other sympatric predators and parasites in these agroecosystems.We studied these by firstly assessing the impact of the weaver ant on the abundance and diversity of the spider community in mango orchards of Senegal. Secondly, we evaluated whether the weaver ant was a good candidate for entomovectoring (transport and dispersal of an agent by an insect vector) of an entomopathogenic fungus (Metarhizium anisopliae) in order to boost their biocontrol efficiency.Ant interactions with the spiders resulted in a neutral to positive impact, showing increased abundances for certain families and not resulting in the exclusion of any taxa. As to their role as entomovectors, colonies were efficient to limit pre-contact and post-contact contamination with the fungal conidia, resulting in their low dispersal through time and space.We discuss the underlying mechanisms and expose possible further studies. Albeit our doubts as to their use as vectors of microbial pathogens, we have found no reasons to exclude the weaver ant from integrated pest management strategies. |
