The lethal effects of gamma irradiation on larvae of the Huhu beetle, Prionoplus reticularis: a potential quarantine treatment for New Zealand exportpine trees

Gamma irradiation was investigated as a possible method for disinfestation of huhu beetle larvae, Prionoplus reticularis White, in Pinus radiata D. Do n. Larvae of four representative size classes were irradiated at six doses, and the lethal dose (LD99) calculated from mortality data 3 days and 10 da ys post treatment. All larval size classes showed a similar sensitivity to gamma irradiation and required 3677 Gray (Gy) and 2476 Gy for a LD99 3 and 10 days post-treatment, respectively. The penetration of gamma irradiation into pine wood was found to be lowest in freshly cut logs, and decreased li nearly at a rate of 0.698 Gy mm(-1) of wood. The penetration was greatest i n wood that had been stored for 2 years, and decreased 0.512 Gy mm(-1) of w ood. These results are likely to be correlated with wood moisture content. Gamma irradiation appears to be a potential alternative method to fumigatio n for quarantine treatment of P. reticularis.