Optimization of Brewer’s Yeast Quantity in Liquid and Gel Larval Diets for the Mediterranean Fruit Fly

SIMPLE SUMMARY: Management of the Mediterranean fruit fly (medfly) with the application of the sterile insect technique depends on the production and release of high quality sterile males that can compete with the feral males to induce sterility in the wild population. Larval rearing should be cost-effective and practical. The right balance between the cost of the protein source (the most expensive ingredient) in larval diets and the quality of the adults produced is a key requirement for effective and economically viable rearing. Two types of diet, a liquid and a gel one, were evaluated across different brewer’s yeast concentrations (protein source) based on survival and developmental duration of larvae and survival of adults. Overall, regardless of the type of diet, brewer’s yeast reduction to 50% of its initial quantity did not affect the quality of the adults produced. Although the performance of immature medflies from the gel diet was inferior compared with the liquid diet, an interesting range of developmental duration phenotypes was observed, opening interesting questions for future experimental work. ABSTRACT: Several artificial larval diets have been developed, evaluated and used for mass-rearing of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Teprhitidae). There are several efforts to reduce the cost of rearing and optimize the quality of the produced sterile males that are destined for release in sterile insect release programs. Survival, growth, longevity and reproductive capacity of sterile males are strongly connected with the most expensive ingredient, the brewer’s yeast (protein), in the larval diet. The current study focused on settling the optimal content of brewer’s yeast in a liquid diet and a gel diet. Egg hatch rates, developmental duration of immatures, pupation rate, pupae and adult survival were recorded as indicators of quantity and quality of the produced adults. Egg hatch was higher and larval developmental duration longer in the gel diet. In contrast to the liquid diet, an increase in brewer’s yeast concentration was correlated with increased pupation rate and pupae survival in the gel diet. Reducing brewer’s yeast up to 50% of its initial quantity had no significant effect on the survival of the emerging adults regardless of the diet type. Our findings may contribute to the production of low-cost and effective diets for use in mass-rearing facilities of medflies.