Tolerance of Hylurgus ligniperda (F.)(Coleoptera: Scolytinae) and Arhopalus ferus(Mulsant) (Coleoptera: Cerambycidae) to ionising radiation: a comparison with existing generic radiation phytosanitary treatments
Background: Irradiation is accepted as a phytosanitary treatment for horticultural products by many countries. Irradiation is a potential alternative to chemical fumigation for wood products; however, data supporting its efficacy against potential forestry pests is limited. Methods: Irradiation efficacy data were obtained experimentally for Arhopalus ferus (Mulsant) and Hylurgus ligniperda (F.). The results are compared to existing ionising-radiation treatment data for various bark and woodboring beetles species as found in the International Database on Insect Disinfestation and Sterilization (IDIDAS) and the published literature. Results: Existing IDIDAS records suggest that the effective dose required to sterilise insects in the families Cerambycidae and Scolytinae is < 150 Gy. Estimated LD99 obtained here for the sterility of adult A. ferus were 44. 1 Gy (LD99, ± 15.3, 95% CI) and eggs 40.4 Gy (± 9.8, 95% CI). Our results suggest that an effective sterilisation dose for A. ferus eggs will be from 20 to 40 Gy; however, LD99 dose estimates were not obtained for other life stages. Adult H. ligniperda were more tolerant of radiation with 1.6% of adults producing viable eggs at doses of between 100 and 150 Gy despite 100% sterility being recorded at 75 and 175 Gy. Conclusions: Our results are consistent with existing studies of other bark and wood-boring beetles. The doses tested here were equivalent to, or lower than, those used in previous studies. Arhopalus ferus adults were less tolerant to ionising radiation than the published literature for other Cerambycidae. Further studies with adult H. ligniperda are recommended as 150 Gy represents the upper limit currently reported in IDIDAS for other Scolytinae. An assessment of the potential cost-effectiveness of irradiation as a phytosanitary treatment at the range of doses identified in this study should be conducted before committing to further efficacy testing.