Canola oil as an economical lipid source in gel larval diet for Queensland fruit fly

A new sterile insect technique (SIT) program is currently being developed for management of the Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), the most costly challenge to Australian horticulture in the eastern states. SIT relies on cost-effective mass production of millions of high-quality flies. A recently developed gel larval diet has proven effective, enabling production of large numbers of high-quality flies, but includes some costly ingredients. With a basic diet now available, current research focuses on refining the formulation to deliver a more economical diet. Wheat germ oil (WGO) is the main lipid source in the current Queensland fruit fly gel diet, but is a particularly expensive ingredient and has limited availability. To identify an oil that maintains high productivity and fly quality at reduced cost, the present study assessed production and performance of Queensland fruit flies reared on gel larval diets containing the WGO that was used in previous studies (WGO/M), an alternative WGO (WGO/A), sunflower oil, rice bran oil, and canola oil. Diets containing canola oil ($5.24/liter) performed as well as diets with WGO/M ($116/liter) in terms of parental egg hatch, pupal number, pupal weight, adult emergence, percentage and rate of fliers, sex ratio, fecundity, and fertility (F1 egg hatch), offering a remarkably cost-effective alternative. Costs of oil in Queensland fruit fly production are reduced by ca. 95% per 1,000 flight capable adults ('fliers'). Substantial savings may be made in Queensland fruit fly mass rearing by substituting WGO/M with canola oil in gel larval diets without compromising productivity.