Effect of gamma irradiation on the susceptibility of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) to the infection with nucleopolyhedrosis virus

The sensitivity of irradiated cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), to infection with nucleopolyhedrosis virus (SpliNPV) was evaluated. S. littoralis pupae were irradiated by four low doses of gamma radiation, 40, 60, 80, and 100 Gy, and the sensitivity to viral infection of the resultant F-1 larvae was evaluated. The results indicated that the irradiated F-1 larvae showed high sensitivity to different SpliNPV concentrations. In the case of 1 x 10(3) PIBs/ml concentration, the mortality percentages of F-1 larvae drastically increased to 25.14, 46.53, 93.2, and 91.3% at the doses 40, 60, 80, and 100 Gy, respectively, in comparison to 4.9% for the un-irradiated treatment. The results revealed that the numbers of deposited eggs, hatched eggs, and survived larvae and pupae were reduced at all the radiation doses as compared to the control treatment. The results indicated that 40 and 60 Gy were the effective doses for irradiating S. littoralis male pupae to produce F-1 larvae very sensitive to SpliNPV which may help in baculovirus mass production.