The Bactrocera oleae (Rossi) (Diptera: Tephritidae) problem: the solution seems to be in its own mid-gut

Bactrocera oleae (Olive fruit fly) is one of the major pest of olives in most commercial olivegrowing regions worldwide. The main gut bacterium Candidatus Erwinia dacicola is essential for the fly’s development. The aim of the present work was to inhibit the fitness of B. oleae altering the fly’s microbiome through the use of microbial metabolites. Bioassays were performed using copper oxychloride and two selected metabolites of Trichoderma spp. (harzianic acid and 6-pentyl- α-pyrone). The repellent efficacy of smoke-water, obtained from pyrolysis of various plant materials was also evaluated. Genetic analysis was used to detect variation in the composition of the intestinal microbiota of flies. Harzianic acid and 6-pentyl-α-pyrone were isolated from culture filtrates of T. harzianum and T. atroviride, respectively, using different extraction protocols and chromatographic methods. Whereas, copper oxychloride solutions were obtained using a commercial product, and the antibiotic (Piperacillin) was used as positive control. Flies separated by sex and allowed to feed on the same compound were mixed for mating after 14 days and fresh olives were exposed to females for egg laying. The number of fly stings, eggs and larvae was calculated. Preliminary results from olfactometric tests using smoke-waters showed a significant repulsive effect in a concentration-dependent manner. Males were more sensitive than females. These results can be pursued in the development of new formulations useful in the Integrated Pest Management strategies for olive pests.