Improved larval diets for mass rearing of Queensland fruit fly (Bactrocera tryoni)

Queensland fruit fly (Bactrocera tryoni, (Froggatt), aka Q-fly), is one of the most damaging horticultural pests in Australia. Sustainable methods are needed for Q-fly management. Sterile insect technique (SIT), in which millions of sterile flies are released to reduce pest reproduction, is effective. However, more efficient larval diet formulations are needed for production of high quality flies in a cost-effective mass rearing system. This thesis was conducted with the aim of developing high productivity larval diets for Q-fly mass rearing, and providing new insights into economical and nutritional aspects of larval diet formulation and Q-fly nutritional requirements. Two formulations of 'gel diet' were developed, and these new diets outperformed both traditional solid diets and more recently developed liquid diets, with outstanding benefits for rearing both at laboratory and factory scale. Subsequent investigations improved these formulations by identifying economical and effective yeasts (a source of amino acids) and plant oils (a source of lipids), as well as exploring the roles of specific nutritional components of yeasts and plant oils (fatty acid, vitamin E and amino acid contents). The initial and refined formulations were then investigated over multiple generations, providing further demonstration of the effectiveness of gel diets for mass rearing. In conclusion, the aims of the project were achieved and the gel diets that were developed have been implemented in the new SIT plus fruit fly mass-rearing facility in Port Augusta (South Australia), where they are already producing more than 20 million flies each week. The formulations of gel diet that have been developed for mass rearing of Q-fly could be modified and further developed for mass rearing of other fruit flies around the world, providing an efficient and economical solution for other SIT programs as well as providing a valuable tool for basic studies of nutrition.