Effects of γ-ray irradiation on Dysmicoccus brevipes and Dysmicoccus neobrevipes
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Key Words：Dysmicoccus brevipes, Dysmicoccus neobrevipes, γ-ray irradiation, treatment
Abstract： Dysmicoccus brevipes(Cockerell) and D. neobrevipes (Beardsley) are important pests requiring quarantine treatment at entry and exit ports for tropical fruit such as pineapples etc. In order to establish an effective treatment method for these two mealybugs, Cobalt-60 gamma ray target doses of 80, 130, 180, 230 and 250 Gy were used to irradiate immatures and adults of both species to find the most tolerant stage and the optimal dose range for quarantine treatment. The responses of each species to irradiation displayed a similar pattern. Tolerance to irradiation in both species increased with advancing life stage, with adults being the most tolerant stage. At 230 Gy, no living offspring were produced by surviving female adults irradiated as nymphs, and no irradiated 1st instar nymphs of D. brevipessurvived to adulthood. Although female adults of both D. brevipes and D. neobrevipes, irradiated with 230Gy, produced an F1 generation but no F2 generation was produced. In a large-scale irradiation test, no surviving female adult developed from either 3rd instar nymphs, nor did adults irradiated at 240 Gy produce offspring, indicating that a dose of 240 Gy or above is sufficient to prevent the reproduction of these two mealybug species.