Author
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Webster, Theodore |
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Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only Publication Acceptance Date: 1/20/2008 Publication Date: 6/16/2008 Citation: Webster, T.M. 2008. Preemergence herbicides affect critical period of weed control in cotton [abstract]. Proceedings of the 2008 Southern Weed Science Society Meeting, January 28-30, 2008, Jacksonville, Florida. 61:199. Interpretive Summary: Technical Abstract: Effective weed control systems must eliminate emerged weeds as well as account for subsequent weed emergence. Two common questions associated with herbicide control are: 1) how long can weeds compete with a crop for resources before yield is reduced and 2) when do weeds that emerge late in the season cease to affect crop yield? Studies that address both of these questions will determine the critical period of weed control (CPWC), in which crop yield losses will be minimized to a standard level (i.e. 5%). Field studies were conducted in 2003 and 2004 in Chula, GA to determine the influence of preemergence herbicides (PRE) with soil residual activity on the CPWC. Weed-free and weedy durations in 2-leaf intervals between 2- and 12-leaf cotton were evaluated with and without PRE treatments of pendimethalin + fluometuron. Plots were maintained weed-free using glyphosate. In the absence of PREs, maximum cotton yield loss from season-long interference was 78%. The CPWC was between planting and the 5- to 6-leaf stage, corresponding to the first four weeks of the season. Inclusion of PREs resulted in 37 to 61% yield loss from season-long interference. In 2003, the CPWC occurred between planting and the 3-leaf stage (first 3 weeks of the season). In 2004, a single control event between the 2- and 6-leaf stage of cotton minimized yield loss to 5%. The inclusion of PREs did reduce the CPWC, but effectiveness in other fields will be a function of weed spectrum and how it matches with the efficacy of the herbicides that are used PRE and POST. |
