Gamma Radiation as a Quarantine Treatment for the Mediterranean Fruit Fly (Diptera: Tephritidae)

Effects of gamma radiation on the egg and larval stages of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), were examined. Eggs and larvae were exposed at different ages to a series of gamma radiation doses ranging from 5 to 1,280 Gy. Eggs in the 1st half of their development (1 and 24 h) were very sensitive to irradiation treatment (20 Gy prevented egg hatch). However, mature eggs (48 h old) were much more tolerant. When mature eggs were irradiated, a dose of 640 Gy prevented egg hatch. Pupariation of eggs treated at 1 and 24 h was significantly affected at a dose of 20 Gy; adult emergence of eggs at 1, 14, and 48 h was prevented at this dose. The larval stage was significantly more resistant to radiation than the egg stage. Survival to the pupal stage increased with increasing age of larvae, and decreased with increasing dose. The minimum dose required to prevent pupariation ranged from over 160 Gy for the 1st instar to > 640 Gy for mature 3rd instars. In contrast, doses required to prevent adult emergence from irradiated larvae were relatively low and ranged from 10-20 to 20-40 Gy depending on the age of the insects when irradiated. Tests in which > 100,000 mature larvae were treated in air with a dose of 40 Gy resulted in no adult emergence. Similar results were obtained when 3rd instars were irradiated inside natural host fruits in a small scale laboratory experiment.