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Post-teneral diets containing yeast hydrolysate are reported to increase longevity, reproductive development and sexual performance of Queensland fruit fly (‘Q-fly’) Bactrocera tryoni Froggatt (Diptera: Tephritidae). Consequently, diets including yeast hydrolysate are recommended for sterile Q-flies before release in sterile insect technique (SIT) programmes. However, in some tephritids, diets including yeast hydrolysate are associated with an increased vulnerability to starvation. In the present study, the effects of yeast hydrolysate supplementation before release are considered with respect to the longevity of released Q-fly when food becomes scarce. Experiments are carried out in three settings of varying resemblance to field conditions: 5-L laboratory cages, 107-L outdoor cages and 14 140-L field cages containing potted citrus trees. In all experimental settings, compared with flies that received only sucrose, male and female Q-flies that are provided with yeast hydrolysate during the first 2 days of adult life have a significantly shorter survival when subsequently deprived of food. Yeast supplementation appears to commit Q-flies to a developmental trajectory that renders them more vulnerable to starvation. The practical significance of these findings for SIT depends on how often the releases are carried out under conditions in which Q-flies experience extreme food shortages in the field.

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.

The great variability of the aphid life cycle and their tendency for host alternation gives rise to aphid clones and morphs. Inter- and intraclonal variability may be observed in the responses of aphids to various environmental factors. In this study we aimed to evaluate the influence of intrinsic factors (clone and morph type) on the intrinsic rate of increase (rm) of the English grain aphid, Sitobion avenae (Fabricius), and the bird cherry-oat aphid, Rhopalosiphum padi (Linnaeus). For each species four apterous clones were collected from established laboratory colonies and compared to assess their relative fitness on high- and low-nitrogen wheat plants under laboratory conditions. The clones had significantly different intrinsic rates of increase on high- and low-nitrogen plants. All R. padi clones had a higher intrinsic rate of increase and mean relative growth rate than S. avenae. Experiments were also conducted to compare the mean fecundity of apterous and alate morphs of S. avenae and R. padi clones on high- and low-nitrogen wheat plants. On high-nitrogen plants the apterous morphs of S. avenae clones had significantly higher mean fecundity than alate morphs. There were no significant differences between the mean fecundity of alate morphs of the same species on high- and low-nitrogen plants. The results support the idea of better fitness of specific clones/morphs on certain host plants due to higher and lower intrinsic rates of increase.