Many covered crops meet serious problems regarding the regulations of aphids. By feeding on sap produced in the vessels of the phloem, aphids do weaken the plants. Furthermore, the massive production of honeydew can lead to the development of sooty mold, a cryptogamic disease. It impacts photosynthesis and spoils the fruits which may lead to a lesser product quality. Biological control of aphids is generally based on a coupled introduction of predators (green lacewings, syrphid flies, cecidomyiidae) and of parasitoids (parasite insects whose development induces the death of the host aphid). Yet there are sometimes obstacles to biological control because of parasitoid biological control efficiency factors, notably for strawberry crops.
So as to optimize aphid biological control, it is crucial to know the pest and auxiliary communities present in the affected crop system. The first study to be presented is the analysis of space and time variability of aphid and parasitoid communities for strawberry crops. For two consecutive years samples of aphids and their parasitoids were taken in various production environments at the national level. This study determined the key species involved in aphid regulation.
During inundating releasing, factors linked to the biology or ecology of the species may limit the efficiency of these auxiliaries. Aphids are known for hosting symbiotic bacteria that can play a role in parasitism resistance. The second study aimed at determining if symbiotic bacteria associated to aphids may limit the efficiency of parasitoids for covered strawberry crops. We first assessed the prevalence of symbiotic bacteria in strawberry aphids nationally. Then we measured the level of protection granted by these symbiotic bacteria thanks to parasitism laboratory tests. Our study thus evidenced that symbiotic bacteria can partly explain the observed inefficiency of parasitoids.
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