Lethal effect of gamma radiation on some post harvest insects of certain fruit and vegetable crops

The objective of the present study is to investigate the lethal dose level of gamma radiation applied against different stages of Mediterranean fruit fly, peach fly and potato tuber moth, determine the efficiency of gamma irradiation as post harvest treatment to eradicate the insect infesttion of guava, peach fruit and potato tubers the effective lethal dose, of gamma irradiation required to applied on infested guava and peach fruits as well as potato tubers to stop the insect survive before cooling storage. Also the effects of applying lethal dose on the physical and chemical properties of the treated fruits and vegetables were investigated. Based on LD5o and LD9o, the egg stage proved to be more radiosensitive followed by pupal and larvae stages of the tested flies and moths. Also, all stages of potato tuber moth proved more radio tolerant than both of Mediterranean and peach fruit flies. While peach fruit fly stages showed the same or more radio tolerant The dose levels of 1.6 and 2 KGy could be considered as the fatal gamma irradiation dose for all Mediterranean fruit fly and peach fly stages, respectively. The dose of 2.8 KGywas the fatal dose for all potato tuber moth stages when irradiated directly. The effective dose of gamma radiation required to disinfest guava and peach fruits artificially infested with the eggs and larvae of fruits flies were 2 and 2.5 KGy for guava and peach respectively .Also, a dose of 2.8 KGy was suggested to inhibit the development and survival of potato tuber moth. The effect of suggested gamma irradiation to applied on guava and peach fruits as well as potato tubers properties during 21, 28 and 90 days of cooling storage was summarized, comparing with unirradiated stored crops, as following decrease in the percentage of discarded fruits and potato tubers. Data indicated significant increase in fruit firmness, insignificant effect on potato tubers, insignificant increase in total soluble solids of fruits, significant decrease in L-ascorbic acid in fruits and significant increase in potato tubers, significant decrease in respiration rate in fruits and insignificant in potato tubers, significant decrease in total phenols in fruits and insignificant in potato tubers, insignificant decrease in total sugar in peach fruit and significant increase in potato tubers, insignificant increase in moisture rate of potato tubers, insignificant increase in total starch of potato tubers, insignificant increase in carotenoids content of guava fruits, significant decrease in total anthocyanin in peel and significant increase in pulp of peach fruits and 100% inhibition in sprouting of potato tubers. As conclusion, the obtained results indicated that gamma irradiation could be of fruits and potato vegetable recommended as an alternative method to chemical fumigants as post harvest treatment to achieve insect disinfestations and tuber sprouting inhibition and reduce the food losses. Accordingly, this technology improve hygienic quality and safety of food and could be used as an effective quarantine treatment. The suggested applied gamma irradiation dose levels were.2 to 2.8 KGy, while the safe limits recommended by joint FAO/WHO codex Alimenntarius Commission (1984) was 10KGy for irradiated foods.