Bottom-up effects of endophytic Beauveria bassiana on multitrophic interactions between the cotton aphid, Aphis gossypii, and its natural enemies in melon

Entomopathogenic fungi are now known to have an endophytic capacity that induces a wide range of changes in the composition of plant nutrients and/or defensive compounds. These changes could influence interactions between the plant and higher trophic levels. In this study, we evaluated the predation/parasitism efficacy of larvae of the lacewing, Chrysoperla carnea, and the braconid parasitoid, Aphidius colemani, when offered aphids that had been challenged by the entomopathogenic fungus Beauveria bassiana. Aphids were either inoculated directly with a fungal suspension (lacewing bioassay only) or had been feeding on melon plants endophytically colonized by B. bassiana. Our results indicate that B. bassiana application did not significantly influence the number of aphid prey consumed by lacewings, or the time took them to consume each aphid. In a choice bioassay, C. carnea larvae preferred to feed on aphids reared on B. bassiana-colonized plants compared with control plants. In another choice assay, the number of aphids parasitized by A. colemani and their sex ratio were not influenced by whether the aphids had been feeding on B. bassiana-colonized plants or not. Our findings support the hypothesis that endophytic entomopathogenic fungi can be used in combination with other natural enemies, such as predators and parasitoids, in Integrated Pest Management programmes.