Low Doses Gamma Irradiation as Quarantine Treatment for Controlling Bactrocera zonata (Saund, 1841) and Its Impact on Guava Fruits Quality

The current laboratory study investigates the effect of low doses of gamma irradiation range of (5-50 Gy) cesium cell- 137 on the different developmental stages eggs, 1st, 2nd , 3rd instars larvae and pupae of peach fruit fly, Bactrocera zonata. In addition to that the evaluation of phytosanitary irradiation dose on 3rd instar larvae and their effects on the biochemical quality of guava fruits were proven. The findings indicate that irradiation of eggs with dose 25Gy prevents adult emergence, while the dose 45Gy prevents pupation and the dose 50Gy prevents the hatchability of eggs. Moreover, exposure of larvae with the dose 50 Gy resulted in 98.5, 91 and 86 % mortality for the 1st, 2nd and 3rd instars larvae, respectively. No adult emergence was reported in 1st, 2nd and 3rd instars at the dose level 30, 35 and 45 Gy, respectively. The 3rd instar larvae appeared to be the most tolerant stage to radiation treatment than the 2nd and 1st larval instars. When adult emergence was used as a criterion for determination of the effective irradiation dose, 50 Gy was adopted for phytosanitary irradiation dose for B. zonata. Large scale confirmatory tests were applied to 25,000 3rd instar larvae of B. zonata in guava fruits resulting in non- F1 adults’ production with a confidence level of 91.8%. In conclusion, the irradiation dose of 50 Gy induces the inhibition of adult emergence of 3rd instar larvae and is suggested as a possible minimum dose for phytosanitary treatment of B. zonata fruit fly without causing significant effect (p ≤ 0.05) on some biochemical characteristics of guava fruits.