Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 30, 2004
Publication Date: June 1, 2004
Citation: Gore, J., Adamczyk Jr., J.J. 2004. Impact of bollworm feeding on Bollgard and Bollgard II cottons. Proc. Beltwide Cotton Prod. Res. Conf. www.cotton.org/beltwide. Interpretive Summary: The impact of bollworms, a caterpillar pest of cotton, on maturity and yield of insect resistant Bollgard and Bollgard II cottons was investigated in field cage studies during 2002 and 2003. The treatments included three (2002) and five (2003) levels of infestation for four durations of infestation. The levels of infestation included 0, 50, and 100 percent of white flowers in 2002; and 0, 10, 25, 50, and 100 percent of white flowers in 2003. The durations of infestation included one to four weeks during the flowering period. When greater than 10 percent of white flowers were infested with bollworms for at least one week, maturity was significantly delayed and yields were reduced in Bollgard cotton. In this study, bollworms did not negatively impact maturity or yields of Bollgard II cotton. These data will be important for defining injury levels on Bollgard and Bollgard II cottons. This in turn will allow for the development of accurate action thresholds to prevent economic losses from bollworms in Bollgard and Bollgard II cottons.
Technical Abstract: The introduction of Bollgard® cottons that produce the Cry1Ac protein from Bacillus thuringiensis Berliner has reduced the numbers of insecticide applications targeting lepidopteran pests of cotton. However, some insecticide applications are still required to suppress bollworms, Helicoverpa zea (Boddie), on Bollgard cotton. Currently, little information exists about bollworm injury to Bollgard cotton and subsequent yield losses. Also, no information exists about the impact of bollworms on Bollgard II® cottons that produce two B. thuringiensis proteins (Cry1Ac + Cry2Ab). A field cage experiment was designed to investigate the impact of bollworms on Bollgard and Bollgard II cottons. Bollworms were artificially infested in plots of Bollgard and Bollgard II cotton in 2002 and 2003. In 2002, bollworms were infested at 3 levels of white flower infestation (0, 50, and 100%) for four weeks. In 2003, the experiment was expanded to also include 10 and 25% infestation levels. Bollworms caused significant delays in maturity and yield reductions in Bollgard cotton when greater than 10% of white flowers were infested for over one week. In this study, bollworms did not negatively impact Bollgard II cotton. These data will be important for defining economic injury levels for bollworms in Bollgard and Bollgard II cottons. Defined economic injury levels will be important for refining current action thresholds for bollworms on Bollgard and Bollgard II cottons.