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 Mediter ranean fruit fly Ceratitis capitata (Wiedemann), were examined. Eggs a nd larvae were exposed at different ages to a series of gamma radiatio n doses ranging from 5 to 1,280 Gy. Eggs in the 1st half of their deve lopment (1 and 24 h) were very sensitive to irradiation treatment (20 Gy prevented egg hatch). However, mature eggs (48 h old) were much mor e tolerant. When mature eggs were irradiated, a dose of 640 Gy prevent ed egg hatch. Pupariation of eggs treated at 1 and 24 h was significan tly 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 m ore resistant to radiation than the egg stage. Survival to the pupal s tage increased with increasing age of larvae, and decreased with incre asing dose. The minimum dose required to prevent pupariation ranged fr om over 160 Gy for the Ist instar to >640 Gy for mature 3rd instars. I n 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 ma ture larvae were treated in air with a dose of 40 Gy resulted in no ad ult emergence. Similar results were obtained when 3rd instars were irr adiated inside natural host fruits in a small scale laboratory experim ent.