Gamma irradiation for insect deinfestation damages native Australian cut flowers

Gamma irradiation doses above 0.05 kGy for Geraldton wax, 0.1 kGy for banksia and 1.0 kGy for kangaroo paw caused significant (P <0.05) reductions in flower and foliage vase lives. Doses of greater than 2 kGy and up to 10 kGy were required for immediate 100% kill of the bioassay insects (adult flour beetle, Mediterranean fruit fly adults and larvae, and spotted moth larvae). Pretreating Geraldton wax shoots by cooling them or pulsing them with sugar lessened the detrimental effect of irradiation (0.1 kGy) on vase life. Pretreatment with silver thiosulphate had no positive effect. Irradiation of Geraldton wax shoots in an inert atmosphere (nitrogen) exacerbated irradiation, induced reduction in vase life and increased flower abscission. None of the postharvest treatments tested were sufficiently ameliorative for irradiation to be considered a viable deinfestation treatment for Geraldton wax. (author)