Evaluation of the susceptibility status of spiny bollworm Earias biplaga (Walker) (Lepidoptera: Noctuidae) to Bt cotton in South Africa

Abstract

The bollworm complex of cotton in South Africa consists of the African bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), red bollworm, Diparopsis castanea (Hamps.) (Lepidoptera: Noctuidae), and the spiny bollworms, Earias biplaga (Walker) (Lepidoptera: Noctuidae) and Earias insulana (Boisduval) (Lepidoptera: Noctuidae) (Green et al. 2003). Larvae of these species are regarded as major pests of cotton since they tunnel into the growing tips, flowering buds and cotton bolls, resulting in damage and subsequent yield losses (Bennett 2015). Genetically modified (GM) transgenic Bt cotton plants that express Cry proteins have been cultivated in SouthAfrica since 1998 to control these lepidopteran pests (Thirtleet al. 2003). Bollgard®, expressing the Cry1Ac protein, was first commercially produced in South Africa in 1998 and discontinued after the 2010 growing season (ICAC 2007). Bollgard ll®, also registered for control of lepidopteran pests on cotton, is a stacked transgenic cotton which expresses two Bt proteins, namely Cry1Ac and Cry2Ab2 (Taverniers et al. 2008; Showalter et al. 2009)