Bill Woods

Irradiation of Adult Epiphyas postvittana (Lepidoptera: Tortricidae): Egg Sterility in Parental and F1 Generations

ABSTRACT Adult Epiphyas postvittana Walker were irradiated using a Cobalt 60 source to determine the dose needed to achieve complete egg sterility of mated female moths, and egg sterility of female moths mated to F1 generation males. Adult male and female E. postvittana were irradiated at 100, 200, 250, and 300 Gy and their fertility (when crossed with normal moths) was compared with nonirradiated moths. Viable progeny (determined by egg hatch) were found at doses of 100 and 200 Gy, but very little at 250 and 300 Gy. In particular, there was no survival of female progeny into the F1 generation. Males irradiated at 250 and 300 Gy had very low egg eclosion rates (2.25 and 1.86% at 250 and 300 Gy, respectively) when mated with normal females. The F2 generation from those male progeny had a mean percent hatched of <1.02%. Based on our results, a dose of 250–300 Gy is recommended for irradiation of E. postvittana adults used for sterile insect technique (SIT) if sterility of parental moths is the desired outcome. Our data also suggests that inclusion of F1 hybrid sterility rather than parental generation sterility into programs using the SIT may allow for doses lower than what we have reported, especially during initial phases of an eradication program where increase fitness of moths might be desirable. Further research is needed to verify the use of F1 hybrid sterility in light brown apple moth SIT programs.

Radiation Biology and Inherited Sterility of Light Brown Apple Moth (Lepidoptera: Tortricidae): Developing a Sterile Insect Release Program

ABSTRACT The radiation biology of two geographically isolated populations of the light brown apple moth [Epiphyas postvittana (Walker)] was studied in Australia and New Zealand as an initiation of a SIT/F1 sterility program. Pharate and ≤2 d pre-emergence pupae were exposed to increasing radiation doses up to a maximum dose of 300 Gy. Fertility and other life history parameters were measured in emerging adults (parental) and their progeny (F1–F3 adults). Parental fecundity was significantly affected by increasing irradiation dose in pharate pupae only. For both populations, parental egg fertility declined with increasing radiation. This was most pronounced for the irradiated parental females whose fertility declined at a higher rate than of irradiated males. At 250 Gy, females ≤2 d preemergence pupae produced few larvae and no adults at F1. No larvae hatched from 250 Gy-irradiated female pharate pupae. At 300 Gy, males still had residual fertility of 2–5.5%, with pharate pupae being the more radio-sensitive. Radiation-induced deleterious inherited effects in offspring from irradiated males were expressed as increased developmental time in F1 larvae, a reduction in percent F1 female survival, decreased adult emergence and increased cumulative mortality over subsequent generations. Males irradiated at ≥150 Gy produced few but highly sterile offspring at F1 and mortality was >99% by F2 egg.

Modeling the Sterile Insect Technique for Suppression of Light Brown Apple Moth (Lepidoptera: Tortricidae)

ABSTRACT A population model was derived for light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), subject to the sterile insect technique (SIT). The model was parameterized from the literature and from recent laboratory studies conducted in New Zealand and Australia. Relationships were fitted for several model parameters that vary with irradiation dose, allowing the model to simulate effectively complete sterility at 300 Gy through inherited sterility occurring from lower doses. At 300 Gy, the model suggests that eventual population extinction is 95% probable when the ratio of released to wild males in monitoring traps exceeds 6.4. Higher overflooding rates would be required to achieve eradication more rapidly. The optimal release interval, in terms of minimizing the required rate of production of factory moths, is approximately weekly. There is little advantage in releasing males only compared with releasing both sexes. Female-only releases are unlikely to be a useful tool for inherited sterility eradication because there is no reduction in the fertility of F1 offspring. The critical release rate required to halt population increase declines with decreasing irradiation dose, but at doses of <171 Gy there is a risk that irradiated-lineage moths may form a self-sustaining population, making eradication by SIT alone impossible. The model suggests that a dose of around 200 Gy may be optimal because the resulting inherited sterility would reduce by a third the number of factory moths required compared with 300 Gy.

Mobile mating disruption of light‐brown apple moths using pheromone‐treated sterile Mediterranean fruit flies

BACKGROUND Public opposition to aerial application of sex pheromone for mating disruption of light-brown apple moth (LBAM), Epiphyas postvittana (Walk.), in California stopped its further use in the ca

Feasibility of Mating Disruption for Agricultural Pest Eradication in an Urban Environment: Light Brown Apple Moth (Lepidoptera: Tortricidae) in Perth

74 million eradication programme in 2008, underscoring the need for other eradication tactics. It is demonstrated that pheromone-treated sterile Mediterranean fruit flies (medflies), Ceratitis capitata Wied., can disrupt communication in male moths. RESULTS Medflies topically dosed with moth pheromone (E)-11-tetradecenyl acetate showed a no observed effect level (NOEL) of ~10 µg fly(-1) , with increasing toxicity from 30 to 100 µg fly(-1) . Greater potency and longevity of attraction and lower mortality were achieved using microencapsulated pheromone. Releases of 1000 pheromone-treated medflies ha(-1) prevented male moth catch to synthetic lures in treated 4 ha plots for 1 day in suburban Perth, Australia. Releases of ca 3000 pheromone-treated medflies ha(-1) disrupted catch to single female moths in delta traps, and to synthetic pheromone lures. Percentage disruption on the first four nights was 95, 91, 82 and 85%. CONCLUSIONS Disruption of moth catch using pheromone-treated medflies is a novel development that, with future improvement, might provide a socially acceptable approach for application of the insect mating disruption technique to control invasive insects in urban environments. Adequacy of payload and other issues require resolution.

Developing Field Cage Tests to Measure Mating Competitiveness of Sterile Light Brown Apple Moths (Lepidoptera: Tortricidae) in Western Australia

ABSTRACT Eradication technologies are needed for urban and suburban situations, but may require different technologies from pest management in agriculture. We investigated mating disruption of a model moth species recently targeted for eradication in Californian cities, by applying dollops of SPLAT releasing a two-component sex pheromone of the light brown apple moth in 2-ha plots in low-density residential Perth, Australia. The pheromone technology was applied manually at ∼1.5 m height to street and garden trees, scrubs, and walls at 500 dollops per hectare of 0.8 g containing ∼80 mg active two-component pheromone. Catches of male moths were similar among all plots before treatment, but in treated areas (six replicates) pheromone trap catches were substantially reduced for up to 29 wk posttreatment, compared with untreated control plot catches (three replicates). The treatment with pheromone reduced catch to virgin females by 86% (P < 0.001) and reduced the occurrence of mating by 93%, compared with three equivalent untreated control plot catches (P < 0.001). Eradication programs are following an upward trend with globalization and the spread of invasive arthropods, which are often first detected in urban areas. Eradication requires a major increase in the communication distance between individuals, but this can be achieved using sex pheromone-based mating disruption technology, which is very benign and suitable for sensitive environments. The need for new socially acceptable tools for eradication in urban environments is likely to increase because of increasing need for eradications.

Mitochondrial Single Nucleotide Polymorphisms in Ceratitis capitata (Diptera: Tephritidae) Can Distinguish Sterile, Released Flies from Wild Flies in Various Regions of the World

Abstract The Australian light brown apple moth (LBAM) (Epiphyas postvittana) (Walker) (Lepidoptera: Tortricidae) is a pest in Australia, New Zealand and now California (USA). The use of sterile insects in combination with mating disruption and biological insecticides has the potential to eradicate outbreaks in urban areas. The sexual competitiveness of irradiated insects is an important component of the effectiveness of the sterile insect technique (SIT), but standard techniques to measure the sexual competitiveness have been developed only for irradiated tephritid fruit flies. In particular, field cage trials have been used to measure the compatibility and competitiveness of irradiated fruit flies in comparison with wild fruit flies. Trials were carried out to determine if such tests could be adapted for a moth species. Parameters of quality or competitiveness evaluated were the proportion of the moths that mated, relative sterility index, index of sexual isolation, and mating competitiveness based on the egg hatch in the various crosses. Results showed that with the release of sterile moths of both sexes (bisex) there was little difference in competitiveness—expressed as the Relative Sterility Index (RSI)—between moths irradiated at 200, 250 and 300 Gy (irradiated either in the pupal or adult stages), but if a Fried competitiveness test was used to generate competitive C values then greater competitiveness was found at the lower doses of irradiation, but this difference was not statistically significant. Modified test procedures were developed in which the moths in field cages—after having had sufficient opportunity to mate—were egged individually and dissected to determine the presence of 1 or more spermatophores; then egg sterility and spermatophore presence were used to determine the mating type, e.g., wild female × irradiated laboratory male, etc. Results indicated that sterile-male-only releases have the potential to increase mating competitiveness of the released irradiated moths, but this conclusion requires additional experiments for confirmation.

Is the Combination of Insecticide and Mating Disruption Synergistic or Additive in Lightbrown Apple Moth, Epiphyas postvittana?

ABSTRACT In areas infested with pest species such as the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), many programs rely heavily on the sterile insect technique (SIT) as a form of biological control. However, when SIT treatments are used both for control of established infestations and for occasional outbreaks, for several reasons, programs are often unable to adequately quantify the success of this approach. Chief among these are difficulties associated with reliably and rapidly determining the strain of origin of males recaptured during and after the SIT program. In this study, we describe the use of a DNA-based marker that can be used to rapidly and reliably distinguish males originating from the two sterile strains that are most widely used in SIT rearing facilities from males originating from wild strains of various regions of the world. This method uses polymerase chain reaction amplification of material from individual specimens to directly analyze DNA sequence variants found within a portion of the mitochondrial ND4 subunit 4 (ND4) gene to identify single nucleotide polymorphisms (SNPs) that are diagnostic of different strains. Specifically, the SNPs described here reliably distinguish individual flies originating from the Vienna 7 and Vienna 8 strains used for sterile release from wild flies infesting various areas including Western Australia, Guatemala, and Hawaii. The availability of such markers for determination of the strain of origin of specimens, either from whole specimens or body parts (including their sperm), has great potential to improve the ability to monitor and quantify the success of any sterile release program.

Stable isotope markers differentiate between mass-reared and wild Lepidoptera in sterile insect technique programs

Pest suppression from combinations of tactics is fundamental to pest management and eradication. Interactions may occur among tactical combinations and affect suppression. The best case is synergistic, where suppression from a combination is greater than the sum of effects from single tactics (AB >> A+B). We explored how mating disruption and insecticide interacted at field scale, additively or synergistically. Use of a pheromone delivery formulation (SPLAT™) as either a mating disruption treatment (i.e. a two-component pheromone alone) or as a lure and kill treatment (i.e. the two-component pheromone plus a permethrin insecticide) was compared for efficacy against the lightbrown apple moth Epiphyas postvittana. Next, four point-source densities of the SPLAT™ formulations were compared for communication disruption. Finally, the mating disruption and lure and kill treatments were applied with a broadcast insecticide. Population assessment used virgin female traps and synthetic pheromone in replicated 9-ha vineyard plots compared with untreated controls and insecticide-treated plots, to investigate interactions. Lure and kill and mating disruption provided equivalent suppression; no additional benefit accrued from including permethrin with the pheromone suggesting lack of contact. The highest point-source density tested (625/ha) was most effective. The insect growth regulator methoxyfenoxide applied by broadcast application lowered pest prevalence by 70% for the first ten weeks compared to pre-trial. Pheromone addition suppressed the pest further by an estimated 92.5%, for overall suppression of 97.7% from the treatment combination of insecticide plus mating disruption. This was close to that expected for an additive model of interactivity between insecticide and mating disruption (AB = A+B) estimated from plots with single tactics as 98% suppression in a combination. The results indicate the need to examine other tactical combinations to achieve the potential cost-efficiencies of synergistic interactions.

From integrated pest management to integrated pest eradication: technologies and future needs.

Abstract In this study we identified a number of moth (Lepidoptera) species that are potential targets for the sterile insect technique (SIT), and we assessed the feasibility of using stable isotope signatures as markers to distinguish mass-reared from wild moth species. Large natural differences in the isotopic signatures of commercially available sugars render them novel markers for mass-reared insects. Sugar beet (Beta vulgaris L.; Caryophyllales: Amaranthaceae), a C3 plant, has a stable isotopic signature (a measure of the ratio of the stable isotopes 13C:12C) of around -27‰ relative to Vienna Pee Dee Belemnite (VPDB; the international C isotope standard for the stable isotopes, 13C and 12C), and sugarcane (Saccharum spp.; Poales: Poaceae), a C4 plant, has an isotopic signature of around -11‰. Thus by means of such a distinct isotope ratio in the sugar in the diet, mass-reared insects can be easily distinguished from wild insects with a high degree of certainty. It was shown that the method could be extended using a multiple isotope approach, with 15N or a full suite of C, N, S and O isotopes. Intrinsic isotope marking of mass-reared moths proved to be an accurate means of distinguishing wild from mass-reared populations, based on isotopic differences between the wild host plant species and the diets used in mass-rearing, which where possible, had been manipulated to contain the isotopically divergent sugar type. This intrinsic labeling using stable isotopes could be useful in the assessment of the quality of mass-reared moths, because a stable isotope is a marker that does not affect the insect in any detrimental manner.