Methoprene and dietary yeast as pre-release supplements for Queensland fruit fly SIT: a thesis submitted for the degree of Master of Research October 2015

Sterile insect technique (SIT) is an environmentally benign pest management technique that relies on released sterile males mating with, and curtailing reproduction of, wild females. Juvenile hormone analogue methoprene (M+) incorporated into pre-release diet (Y+ sucrose plus yeast, Y- sucrose only) was studied as a potential enhancer of reproductive organ development, sexual maturation, and longevity of Queensland fruit fly Bactrocera tryoni (Froggart), or 'Q-fly' used for SIT. Incorporatoration of methoprene into diets that also contain yeast was found to strongly accelerate reproductive organ development (testes and apodeme) in males, but had much weaker effects on females (ovaries). Age, detary yeast and methoprene application all increased male mating success at early ages. Yeast and methoprene had synergistic effects on sexual maturation, since M+Y+ treated males exhibited increased mating propensity at younger ages than either M+Y- or M-Y+ flies. Flies provided yeast had increased mating success in comparison to yeast-deprived flies. In the absence of yeast, methoprene (M+Y-) treatment had only a modest effect on sexual maturation. In contrast to males, female Q-flies exhibited little response to methoprene treatment. Both when held individually in small cages and in groups in larger cages, yeast supplementation resulted in longer life spans for both males and females with and without methoprene, but methoprene did not significantly affect longevity. Longevity was higher when the flies were in larger group cages rather than in individual cages. Overall, these results show great promise and encourage direct incorporation of methoprene into yeast diet as a pre-release treatment for Q-fly SIT.