Effectiveness of irradiation as a quarantine treatment against various fruit fly species

Research on the effects of gamma irradiation on immature fruit flies has been conducted for over 30 years. The objectives of this research were to obtain the data required to develop dose mortality curves, to predict the dose required for quarantine security and to confirm that this dose was adequate. Studied on several species of fruit fly have shown that there is a variation in their sensitivity to radiation. Differences between species, differences in the age and stage of development of the flies being tested and differences in the experimental techniques used could account for much of the variation observed. The dose of radiation required to reduce egg hatch, larval pupation or adult emergence by 95% when applied to fruit fly eggs or larvae was used as a basis for comparison of the effects of irradiation on different species of fruit fly. Doses of <36 to >1000 Gy were required to reduce egg hatch, depending on the age of the eggs. Usually, <50 Gy applied to the eggs reduced pupation and <35 Gy reduced adult emergence by 95%. Doses of up to 700 and <50 Gy applied to immature larvae reduced pupation and adult emergence by 95%, respectively. For mature larvae, doses of up to 1600 Gy were required to reduce pupation by 95%, but less than 50 Gy reduced adult emergence by 95%. Higher doses, up to 80 Gy, were required to reduce adult emergence by 95% when mature larvae were treated in fresh medium or in medium with water added. In general, exposure of fruit fly eggs and larvae to a dose of less than 150 Gy prevented adult emergence, although in some cases the calculated dose for probit 9 (99.9968% mortality) security was estimated to be as high as 280 Gy. Theoretically, X rays or electron beams would have a similar effect on immature fruit flies. However, little research has been done using such source of radiation. (author). 34 refs, 5 tabs