Field longevity of methyl eugenol and cue-lure plugs and associated insecticidal strips: captures of Bactrocera dorsalis and Zeugodacus cucurbitae (Diptera: Tephritidae) in Hawaii.

Certain species of true fruit flies (Diptera: Tephritidae) cause tremendous damage to commercially important fruits and vegetables, and many countries operate continuous trapping programs which rely on male-specific lures such as trimedlure (TML), methyl eugenol (ME), and cue-lure (CL). Traditionally, these attractants have been applied as liquids to cotton wicks inside traps, although this results in high evaporative loss of the lure. Slow-release, polymeric plugs have been widely adopted for TML, but such devices are not widely used for ME or CL. Recent data, however, suggest that ME and CL plugs may be attractive for as long as 12 wk in the field. The present study investigates whether ME and CL plugs weathered for 18 or 24 wk are effective in capturing males of Bactrocera dorsalis (Hendel) and Zeugodacus cucurbitae (Coquillett), respectively. For B. dorsalis, 6 g ME plugs were as effective as the control treatment (fresh liquid on a wick) after 12 wk of weathering but not after 18 or 24 wk. For Z. cucurbitae, 3 g CL plugs were as effective as the control treatment (fresh CL plugs) after 12 and 18 wk of weathering but not after 24 wk. The residual content and release rate of the 2 lures were also measured over time, but, with the exception of the residual content of ME, we did not find a direct correlation between these parameters and numbers of flies captured.

Comparing the biological effectiveness of low energy 100 kV and high energy 5 MeV X-rays against Oriental fruit fly (Diptera: Tephritidae).

Radioisotope irradiators (using cesium-137 or cobalt-60) are used as sources of ionizing radiation to control quarantine or phytosanitary insect pests in internationally traded fresh commodities and to sterilize insects used in sterile insect release programs. There are institutional initiatives to replace isotopic irradiators (producing γ-rays) with lower-energy X-ray machines due to concerns about radiological terrorism and increasingly stringent regulations on the movement of radioisotopes. Questions remain about whether the biological effects of low-energy X-rays are comparable to those of γ-rays since differences in energy levels and dose rates of X-rays may have different efficacies. We compared adult emergence, flight ability, and adult survival in the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritdae), after irradiation of third instar larvae with 100 kV or 5 MeV (5,000 kV) X-rays at 20 and 40 Gy in replicated studies. At 20 Gy, the adult emergence rate was significantly lower after irradiation with 100 kV compared to 5 MeV X-rays, suggesting higher efficacy at the lower energy level. In a follow-up study using 100 kV X-rays, applying 20 Gy using a slow dose rate (0.24 Gy min-1) resulted in significantly higher adult emergence than did a fast dose rate (3.3 Gy min-1), suggesting lower efficacy. Although our study suggests higher efficacy of low energy 100 kV X-rays, there is uncertainty in measuring the dose from an X-ray tube operating at 100 kV using an ionization chamber; we discuss how this uncertainty may change the interpretation of the results. Using a 100 kV X-ray irradiator to develop a phytosanitary treatment may underestimate the dose required for insect control using commercial high-energy γ-ray or X-ray systems.

Phenotypic disruption of cuticular hydrocarbon production in hybrids between sympatric species of Hawaiian picture-wing Drosophila.

Interspecies hybrids can express phenotypic traits far outside the range of parental species. The atypical traits of hybrids provide insight into differences in the factors that regulate the expression of these traits in the parental species. In some cases, the unusual phenotypic traits of hybrids can lead to phenotypic dysfunction with hybrids experiencing reduced survival or reproduction. Cuticular hydrocarbons (CHCs) in insects are important phenotypic traits that serve several functions, including desiccation resistance and pheromones for mating. We used gas chromatography mass spectrometry to investigate the differences in CHC production between two closely related sympatric Hawaiian picture-wing Drosophila species, Drosophila heteroneura and D. silvestris, and their F1 and backcross hybrid offspring. CHC profiles differed between males of the two species, with substantial sexual dimorphism in D. silvestris but limited sexual dimorphism in D. heteroneura. Surprisingly, F1 hybrids did not produce three CHCs, and the abundances of several other CHCs occurred outside the ranges present in the two parental species. Backcross hybrids produced all CHCs with greater variation than observed in F1 or parental species. Overall, these results suggest that the production of CHCs was disrupted in F1 and backcross hybrids, which may have important consequences for their survival or reproduction.