Impairing the development of an olive fly pest by targeting its symbiotic bacteria in egg-infested fruits

The olive fly Bactrocera oleae is an important pest across the world, and its control has traditionally been achieved through synthetic insecticides. Nowadays, there is a growing demand for reducing chemical use due to environmental and human health concerns. The manipulation of symbiotic bacteria inhabiting insect pests has been proposed as a sustainable strategy, allowing insecticide-free management. Here, the possibility of impairing the strict association between the olive fly and its primary symbiont, 'Candidatus Erwinia dacicola', was tested by preventing bacterial infection of the newborn larvae of the pest. Five commercial products with putative antimicrobial activity were used for treating olives infested with eggs. Results showed a significant reduction of the symbiotic bacterial load in larvae derived from olives treated with dodine and a zinc-copper-citric acid biocomplex, as well as a reduction in the pupation rate of the pest. Our findings for the first time provide evidence of the feasibility of impairing the symbiotic association in olive fly through the application of antimicrobial compounds in olive fruit infested with newly laid eggs.