The Effect of Giant Ragweed on Cotton Maturity, Yield, and Fiber Quality

Glyphosate-resistant (GR) weeds are the most problematic weeds species for Tennessee cotton growers.  GR giant ragweed is typically considered a major issue for MidWestern corn and soybean growers, but can also be found throughout the cotton growing areas of Tennessee, Missouri, and Arkansas.  GR giant ragweed was first confirmed in 2007 in Tennessee and has continued to become more problematic throughout this region (Norsworthy et al. 2010).  Previous work in the MidWest has evaluated the effects of GR giant ragweed competition in corn and soybean where one plant per 30 foot plot can reduce yields by 13-25% (Baysinger and Sims 1991; Harrison et al. 2001).  However, little is known about the effects of giant ragweed in cotton.  Therefore a study was conducted to demonstrate the effect of giant ragweed on cotton maturity, lint yield, and fiber quality.  Giant ragweed densities were 0, 1, 2, 4, 8, and 16 weeds per 4 row by 30 ft. plot.  Plots were maintained weed free throughout the growing season.  Cotton heights, NACB (node above cracked boll) ratings were assessed, lint yield was determined, and fiber quality characteristics (micronaire, fiber strength, fiber length, uniformity).  The objective of this study was to determine how giant ragweed would potentially delay maturity, reduce yield and fiber quality at each of these populations.            

 Literature Cited

Baysinger, J. A. and B. D. Sims.  1991.  Giant ragweed (Ambrosia trifida) interference in

soybeans (Glycine max).  Weed Sci.  39:358-362. 

Harrison, S. K., E. E. Regnier, J. T. Schmoll, and J. E. Webb.  2001.  Competition and

fecundity of giant ragweed in corn.  Weed Sci.  49:224-229.

Norsworthy, J. K., P. Jha, L. E. Steckel, and R. C. Scott.  2010.  Confirmation and control

of glyphosate-resistant giant ragweed (Ambrosia trifida) in Tennessee.  Weed Technol. 

24:64-70.