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One possible control strategy against the olive fly, Bactrocera oleae, the most serious olive crop pest, is the Sterile Insect Technique (SIT) application. However, a number of problems associated with this method remain that decrease the effectiveness of SIT, including the quality of reared insects. Taking the importance of the relationship between the olive fly and bacteria into consideration, the effects of probiotic diets enriched with Pseudomonas putida on B. oleae longevity and fecundity were evaluated. First, we found that the probiotic bacterium, P. putida, is conveyed from diets to the oesophageal bulb as well as to the fly midgut after feeding on the probiotic diet. Subsequently, B. oleae adults fed on either: (a) a standard full protein and sugar diet; (b) a sugar only diet; (c) a probiotic standard full protein and sugar diet; or (d) a probiotic sugar diet. Flies fed on probiotic diets were supplied with an inoculated gel containing P. putida; non-inoculated gel was provided to the flies fed on non-probiotic diets. B. oleae males and females that fed on sugar diets did not survive as long as those that fed on protein diets. A comparison of the longevity of adults fed on full diet and sugar with their respective probiotic diets revealed no significant difference. Males fed on the sugar only diet survived longer than males fed on probiotic sugar diet, and females fed on the full protein and sugar diet survived much longer than females fed on the full probiotic diet. As regarding fecundity, both full diets resulted in a higher number of eggs laid per female. Females fed on the probiotic sugar diet laid a higher number of eggs than females that fed on sugar only. The inoculated gel of the probiotic sugar diet contained a significantly higher quantity of leucine, isoleucine and proline than the non-inoculated gel of the sugar only diet. The possible role of dietary bacteria in relation to functional aspects of olive fly physiology is discussed.

Effects of culturing medium on production and emission of volatiles by Pantoea agglomerans (Beijerinck 1888) Gavini et al. 1989 preparations and on attractiveness of the preparations to the Mexican fruit fly, Anastrepha ludens Loew, were investigated. Bacterial cultures in each of four biochemically different types of liquid media emitted different volatiles. Cultures in a medium containing uric acid as its primary nitrogen source emitted more ammonia and 2-nonanone than the other media. We postulate that the high production of ammonia was because of uricase activity by this uricase (+) strain. Regardless of media type, supernatants emitted more volatiles than preparations containing cells that had been removed from whole cultures and put into distilled water. Attractiveness varied little with biochemical make-up of the culturing medium although the uric acid and carbohydrate preparations were as a group more attractive than preparations made from the other two media. Supernatants and whole cultures generally were more attractive than cell preparations and non-inoculated media. Bacteria grown in aqueous uric acid-based media emitted volatiles similar but not identical to those emitted by bacteria grown on gel (agar or solid) uric acid-based media in Petri plates.

The relationship between the olive fly population and epiphytic bacteria of the olive tree was investigated by carrying out a 1-year survey in the field. The olive fly population affected the number of bacteria present on the olive surface. Scanning electron microscope observations demonstrated that bacteria may be ingested by the fly’s mouth apparatus through the midline of the pseudotracheae. DNA amplification of the oesophageal bulb content using 16S bacteria universal primers and DNA sequencing evidenced that Candidatus Erwinia dacicola was the predominant species present. The role of bacteria in olive fly biology is discussed.