Effect of gamma irradiation on reproduction biology, inherited sterility and mating competitiveness of Spodoptera exigua (Lepidoptera: Noctuidae) in laboratory condition

Abstract

The beet armyworm Spodoptera exigua Hübner, is an invasive pest of sugar beet and other field crops and vegetables. Here, the potential of sterile insect technique and inherited sterility to control of Spodoptera exigua have been investigated by pupae irradiation with Co⁶⁰ gamma ray. The emerged adult’s reproduction, sterility, growth biology, sex ratio, mating competitiveness and inherited sterility in P₁ and or F₁ generations were investigated. Completely P₁ sterile females and males were found when pupae were irradiated with 250 and 400 Gy, respectively. Female emergence was significantly reduced at 400 Gy, but their longevity increased with higher doses. When P₁ male or female pupae were irradiated with 250 or 180 Gy respectively, the period of F₁ larvae was longer than the normal. The emergence of F₁ males decreased with increasing dose. When treated male parents were crossed with normal females, the sex ratio of F₁ shifted in favor of males. F₁ progeny showed more sterility than P₁ generation and F₁ males inherited more sterility than F₁ females. Laboratory mating competitiveness indicated that 250 Gy irradiated males (IM) were competitive against untreated males (UM) in mating with untreated females (UF) even at 1:1:1 (IM:UM:UF) ratio.