Effect of gamma irradiation on F1 generation and competitive ability of Phyllocnistis citrella and Ostrinia nubilalis, and evaluation of the sterile insect release ratio on plant infestation in field cages

Abstract

AbstractCitrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), and European corn borer (ECB), Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), are two key pests of young citrus and maize plants in Iran, respectively. In this study, the effects of sub‐sterilizing doses of gamma radiation (100–250 Gy for CLM, 90–180 Gy for ECB) on the biological and reproductive parameters of F1 progeny from irradiated males were determined. The results indicated that males irradiated at doses of ≥200 and ≥150 Gy produced highly sterile F1 descents for CLM and ECB, respectively. No adverse effects of radiation doses applied to males were observed on the F1 pupal emergence for both species, nor on the adult longevity of male and female ECB moths. However, the life span of CLM F1 male and female adults decreased with increasing doses. The sex ratio of emerged adults of F1 progeny from irradiated males was skewed towards males with increasing doses; the proportion of males to all emerged adults reached 0.52 and 0.54 at doses of 250 and 150 Gy for CLM and ECB, compared to 0.44 and 0.49 in the controls, respectively. The competitiveness index of irradiated and F1 males of both species fluctuated in acceptable ranges and in general F1 males were stronger competitors than their irradiated male parents. The results of the field cage experiments showed that the larval infestation in all cages including the released irradiated CLM and ECB moths decreased compared to the control treatment – the percentage of damaged leaves and stems in the cages with ratios of 20:1 and 7:1 irradiated‐to‐normal insects (highest ratios assayed) reached half and one‐third of the control for CLM and ECB, respectively.