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

"The Queensland fruit fly or ‘Q-fly’, Bactrocera tryoni (Diptera: Tephritidae), is Australia’s most economically important insect pest of fruit crops. The Sterile Insect Technique (SIT), which involves the mass rearing and release of millions of sterile flies to curtail reproduction of wild populations, is used as an environmentally benign approach to control Q-fly. High quality larval diets are essential for economical mass rearing and effective SIT. As a first step to development of improved diets, liquid larval diet formulations that have received substantial interest over the past decade (‘Chang 2006’ and ‘Chang 2009’) were compared with a conventional carrot-based solid diet. Results suggested that liquid diets are a promising alternative to carrot diet, but that their performance can be constrained by heterogeneity and high viscosity that can result in high larval mortality. To deal with these issues, the liquid diet formulations were mixed with agar (0, 0.25, 0.5, 1.0 and 1.5%) to produce gel diets. Significant diet by agar group interactions were found for most quality parameters, indicating that development of agar-based diets is a far more complex task that adding a specified proportion of agar to a suitable liquid diet formulation; the ideal proportion of agar to use depends on the diet formulation. Overall, around 1% agar provided the best balance of development rate, productivity and quality parameters. Diet experiments used eggs transported in water, and supplementary experiments confirm that the typical transit time of ca. 2 hours does not reduce hatching rate. These projects set the stage for more detailed investigation of gel diets as the most promising option for mass-rearing of Q-fly for SIT." -- Abstract.