Comparison of Bt Technologies, with and without Diamide Applications for Control of Helicoverpa Zea in Arkansas Cotton

The cotton bollworm (Helicoverpa zea, Boddie) is a major pest of post-bloom cotton in the Mid-South. In Arkansas, 100% of the cotton acres were infested by the cotton bollworm. Transgenic cotton cultivars are planted on 98% of Arkansas’ cotton acreage. With the high input costs associated with these traits and the growing concern with tolerance/ resistance to Bt, it is important to monitor the different traits to evaluate the efficacy for control of caterpillar pests. Recent studies have indicated that dual gene Bt cultivars, such as WideStrike, Twinlink and Bollgard II may not provide the protection needed to prevent fruit damage from cotton bollworms and may require supplemental foliar applications in years when bollworm populations are high. Around 75% of cotton acres in Arkansas receive a supplemental foliar application for control of the cotton bollworm. Arkansas’ cotton bollworm threshold for transgenic cotton cultivars is 6% damaged fruit (squares + bolls) and worms present.