Comparison of Two Potential Methods To Detect Bactrocera tryoni (Diptera: Tephritidae) Gamma-Irradiated for Quarantine Purposes

Abstract

We examined use of both biochemical and anatomical techniques to detect irradiated larvae and pupae of the Tephritid fruit fly Bactrocera tryoni (Froggatt). Electrophoretic protein profiles for control and irradiated larvae were similar, irrespective of the age at which irradiation occurred. Protein profiles for control and irradiated pupae were also similar for the first 2 d of pupation. Anew protein band was detected in control pupae 3 d after pupation began. This band was not observed in any irradiated pupae. However, because pupae cannot be aged morphologically, the absence of this protein band cannot be used to distinguish between irradiated and nonirradiated pupae of unknown age. Dissections of pupae indicated that the new protein band was not present because irradiated pupae died during the first days of pupation. No irradiated pupae survived to emergence. Electrophoretic techniques did not identify consistently either irradiated larvae or pupae of B. tryoni . The corrected size of the supraesophageal ganglion in irradiated mature larvae was significantly smaller than in untreated larvae, regardless of the age at which irradiation occurred. This reduction was ≍64% in samples treated as eggs (26 h), first (72 h), and second (96 h) instars and 34% in third instars. A significant reduction in size of the supraesophageal ganglion of mature third instars from all irradiation treatments suggests that this character may be successfully used to detect B. tryoni irradiated at quarantine dose rates. Irradiated samples had a significantly longer larval and pupation period, possibly because of the inability of irradiated larvae to feed normally. We also observed a significant increase in larval mortality with decreasing age at irradiation.