Potential of liquid larval diets for mass rearing of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Diets for the mass rearing of tephritid fruit flies have traditionally been based on bulking agents, such as lucerne, bran or carrot, which make up the majority of the larval medium. To overcome storage, handling and waste challenges of such ‘solid’ diets, liquid diets have been developed for some species. In liquid diets, reusable inert substrates, such as synthetic sponge, replace bulking agents to support the developing larvae. As a step towards increased production efficiency and quality, this study investigated the efficacy of three liquid diets and four solid diets for mass rearing of Queensland fruit fly, Bactrocera tryoni (Froggatt) (‘Q-fly’). Under similar egg/diet density, diets were assessed in terms of pupal yield, larval duration, pupal weight, sex ratio, % adult emergence, % fliers, rate of fliers, egg/female/day, egging latency, and % egg hatch in both parental and F1 generation. The best liquid diet showed some promise as an alternative to conventional solid diets. Comparing Q-fly reared on the best liquid diet with those reared on lucerne diet revealed mean pupal yield of 1636 ± 106.9 vs. 658 ± 16.2, pupal recovery of 21 ± 0.0% vs. 10 ± 0.0%, egg/female/day of 53 ± 3.8 vs. 30 ± 2.4, parental egg hatch of 85 ± 0.9% vs. 70 ± 1.6% and F1 egg hatch of 87 ± 0.9% vs. 74 ± 1.4%. Liquid diets and their associated rearing systems show potential as efficient, reliable and economical replacements for the current solid diets.