Effect of gamma ray irradiation on egg hatchability and F1 eggs of Tetranychus urticae (Acarina: Tetranychidae) with small scale-up validation

• Hatchability of eggs significantly decreased by increasing doses of gamma ray
• Eggs aged 4 d was the most tolerant to gamma radiation.
• F1 egg hatchability of the irradiated adults decreased with increasing gamma ray dose
• Hatchability of the F1 eggs was prevented by 450 Gy gamma ray in small scale-up test

Effect of gamma ray irradiation was examined on the viability of eggs and adults of two spotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae). Eggs aged from 1 d to 4 d and adults were irradiated at doses of 0, 50, 100, 200, 300, and 400 Gy. Hatchability of the eggs decreased with increased irradiation doses. The 4-d-old eggs were more tolerant to the irradiation compared with younger ones. ED99 for inhibiting hatching was 286, 284, 307 and 656 Gy for 1-d, 2-d, 3-d, and 4-d-old eggs, respectively. Gamma irradiation of at least 400 Gy did not show any changes in mortality and fecundity of adult females within 1 d after treatment. However, hatchability of F1 eggs laid by the irradiated adults was greatly affected. ED99 for inhibiting hatching of the F1 eggs was 302 Gy (95% CL: 238–418 Gy). In small scale-up validation test, irradiation of 450 Gy (absorbed dose: 432–480 Gy) to 1000 female adults caused 100% mortality of F1 eggs (6316 eggs) laid by the irradiated adults. Thus, gamma ray irradiation of 450 Gy could be a practical phytosanitary disinfestation treatment for T. urticae in agricultural commodities.

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