Abstract
The Mediterranean fruit fly, Ceratitis capitata, is a major agricultural pest worldwide. The development of genetic sexing strains (GSSs) for this species that allows male-only sterile insects releases has boosted the effectiveness of the environmental friendly pest control method known as the sterile insect technique. The last generation of these strains, the VIENNA 7 and VIENNA 8, are currently used in all mass rearing facilities worldwide and are considered as models for such pest control applications. The sterile insect technique depends on the rearing of sufficient numbers of adequate “biological quality” laboratory flies to be released in the field. Currently, there is an increasing amount of studies focusing on the characterization of the symbiotic communities and development of probiotic diets. In our study, two bacterial isolates, an Enterobacter sp. (strain AA26) and a Klebsiella oxytoca strain, were used as probiotics in larval and adult diet. These strains have been shown to be beneficial, affecting several aspects related to the rearing efficiency and biological quality of the medfly VIENNA 8D53+ GSS. Our results demonstrate the effect of K. oxytoca on the developmental duration of the immature stages and, to some extent, on flight ability. On the other hand, our study does not support the presence of any beneficial effect of (a) K. oxytoca on pupal and adult recovery and adults’ survival under stress conditions when provided as a larval diet supplement and (b) K. oxytoca and Enterobacter sp. AA26 on mating competitiveness when provided as adult diet supplements. Possible explanations for inconsistencies with previous studies and the need for universalizing protocols are discussed. Our findings, combined with previous studies can support the sterile insect technique, through the improvement of different aspects of mass rearing and biological properties of laboratory reared insect pests.
Highlights
The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), is a cosmopolitan species that poses severe threats to a variety of fruits worldwide (White and Elson-Harris, 1992)
The findings of this study showed that: (a) the addition of bacteria to sterile male diet significantly increased their mating success, both with “wildish” females in laboratory conditions and with “wild” females in semi-natural conditions, (b) bacterially fed sterile males were more effective than sugar fed males in inhibiting female receptivity and, (c) sterile males fed on bacteria enriched diet showed better ability to survive after 48 and 72 h of starvation, compared to the sugar-only fed
Egg to Pupae Recovery Logistic regression analysis revealed that the bacterial concentration (106, 107, or 108 bacteria per gram of larval diet) was not a significant predictor of egg to pupae recovery rates neither for “autoclaved” (Wald’s test t = 3.57, df = 1, P = 0.059) nor for “live” bacteria (Wald’s test t = 3.07, df = 1, P = 0.079)
Summary
The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), is a cosmopolitan species that poses severe threats to a variety of fruits worldwide (White and Elson-Harris, 1992). The extensively studied biology of C. capitata made it a Tephritidae model for the implementation of area-wide control methods, like Sterile Insect Technique (SIT). SIT relies on the mass rearing and release of sterile flies intended to mate with the natural population, causing infertile crosses and subsequent population suppression (Dyck et al, 2005). In most of the cases, in the SIT approach, sterility is delivered through irradiation. The implementation of a large-scale SIT program depends on the feasibility to produce (a) the adequate number of insects in a sustainable cost, and (b) high biological quality insects showing adequate performance and mating competitiveness in the field
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