Ionizing irradiation of adults of Angoumois grain moth (Lepidoptera: Gelechiidae) and Indianmeal moth (Lepidoptera: Pyralidae) to prevent reproduction, and implications for a generic irradiation treatment for insects

Ionizing irradiation is used as a phytosanitary treatment against quarantine pests. A generic treatment of 400 Gy has been approved for commodities entering the United States against all insects except pupae and adults of Lepidoptera because some literature citations indicate that a few insects, namely, the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), and the Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), are not completely controlled at that dose. Radiotolerance in insects increases as the insects develop, so the minimum absorbed dose to prevent F1 egg hatch for these two species when irradiated as adults was examined. Also, because hypoxia is known to increase radiotolerance in insects, Angoumois grain moth radiotolerance was tested in a hypoxic atmosphere. A dose range of 336-388 Gy prevented F1 egg hatch from a total of 22,083 adult Indianmeal moths. Dose ranges of 443-505 and 590-674 Gy, respectively, prevented F1 egg hatch from a total of 15,264 and 13,677 adult Angoumois grain moths irradiated in ambient and hypoxic atmospheres. A generic dose of 600 Gy for all insects in ambient atmospheres might be efficacious, although many fresh commodities may not tolerate it when applied on a commercial scale.