Fruit flies cause severe economic losses in fruti- and viticulture in the Mediterranean basin. Triggered by ongoing climate change, the spread of invasive fruit fly species from Northern Africa to Mediterranean EU and Central European countries potentiates the threat to farmers. One highly specialized fruit fly of particular economically relevance for Mediterranean countries is the Olive Fly, Bactrocera oleae. The pest deposits its eggs into unripe olives, larvae develop within and feed on the ripening fruit, holding potential to infest entire harvests if uncontrolled. Infested fruit is no more suitable for consumption as table olive or for olive oil production.
Olive Fly management by chemical insecticides is both technically challenging due to the protected location of the larvae and problematic due to the enrichment of insecticide residues in olive oil. Therefore, microbial fruit fly pathogens with innovative modes of action are increasingly solicited to be developed into new biological control products. Fruit flies are generally associated with a diverse bacterial microbiome. The Olive Fly is stably associated with an obligatory symbiont, Candidatus Erwinia dacicola, and secondary symbionts of varying number, diversity and functional relationships.
During the past decade, bacteria from different species of the genus Providencia have been found associated with and pathogenic to fruit flies as the common vinegar fly, Drosophila melanogaster, the Mexican fruit fly, Anastrepha ludens, and the Mediterranean fruit fly, Ceratitis capitata. Providencia bacteria have properties potentially facilitating the development of Biological Control or Integrated Pest Management strategies as, e.g. being the insecticidal agent associated with entomoparasitic nematodes or attracting both male and female fruit flies from several Bactrocera species. In 2018, the new bacterial species Providencia entomophila has been identified in both olive flies and olive fly larvae from Tunisian olive groves.
In front of this scientific background, it has been the overall objective of the OliveFlyBacteria project:
• to identify Providencia bacteria - and especially Providencia entomophila - from Olive Fly populations across Southern Italy,
• to evaluate the biocontrol potential of the new Olive Fly associated Providencia isolates, and
• to lay a methodological basis for studies of the molecular interaction of Providencia bacteria and their Olive Fly host.
