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Early Season Weed Management in Cotton

Posted 3/31/2017
Successful, season-long weed management begins with a burndown application, that includes a residual herbicide, to kill emerged weeds and prevent additional weeds from emerging in cotton.

Successful, season-long weed management begins with a burndown application, that includes a residual herbicide, to kill emerged weeds and prevent additional weeds from emerging in cotton. Growers should then follow with a PRE application of residual herbicides plus an additional burndown herbicide at planting. After cotton emergence, most growers should make one or two POST herbicide applications. At layby, late-emerging weeds may be controlled using a hooded sprayer or directed sprayer. Large weeds may need to be removed by hand.

Cotton is sensitive to weed competition during the early growth stages. Effective pre-plant weed control conserves soil moisture, facilitates planting by providing a clean seedbed, and helps provide critical weed control through planting and after crop emergence.

Importance of Timing Weed Management

Timely weed management can help maximize cotton yield potential. Studies conducted at the Learning Center in Leland, Mississippi in 2007 and Scott, Mississippi in 2008 to evaluated the yield response of cotton to delayed weed control.1 Results from the trials showed cotton yields were reduced when cotton did not receive timely early-season weed control. Cotton yields were reduced by 21%, 37%, and 46% when weed control was delayed by 14, 21, and 28 days, respectively. Additional results indicated that weeds were controlled best when small and cotton plants became stunted relative to delayed weed control (Figures 1 and 2).

Figure 1
Figure 1. Vigorous, well developed cotton with optimal herbicide application timing (1 to 2 leaf cotton).
Figure 2
Figure 2. Weed competition visibly stunted cotton growth and yield potential when herbicide application was delayed 28 days after optimal timing.

For best management, weeds should be controlled as early as possible. Applications of herbicides to weeds that are bigger than the label requirements will experience reduced control and enable increased weed survival. In Genuity® Roundup Ready® Flex or Bollgard II® XtendFlex® cotton, the use of Roundup® brand glyphosate-only agricultural herbicides can be an effective and economical tool for weed control when properly applied. Along with Roundup brand glyphosate-only agricultural herbicides, the use of residual herbicides in a weed control program can be an integral practice for combating tough-to-control weeds. Certain residual herbicides can be tank-mixed with Roundup brand glyphosate-only agricultural herbicides. Refer to product label for tank-mixing partners and instructions for use. As weed populations become more difficult to control, it is recommended that a season-long weed management program be established that includes herbicide applications at pre-plant, early POST, and layby.

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