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.