Development of Treatment Thresholds for Bollworm (Helicoverpa zea) In Second-Generation Bt Cotton

Second-generation Bt cotton technologies, Bollgard II and Widestrike have been available commercially since 2003 and 2005, respectively. The different combinations of genes and toxic proteins produced by the two technologies create measurable differences of in-plant control for caterpillars. Current threshold recommendations for both Bollgard II and Widestrike are based on those for original, first-generation Bollgard cotton. This research aims to develop specific action thresholds for two-gene Bt cotton as well as explore the subtle differences between Bollgard II and Widestrike. Data from one growing season regarding density of bollworm eggs, larvae, and boll damage were measured and analyzed in relation to yield data.