Source: Allen Press


Farmers who use herbicide-tolerant crops face a growing challenge from herbicide-tolerant and herbicide-resistant weeds, which are evolving and spreading across cropland.


In the southeastern United States, weeds that can tolerate or resist the popular herbicide glyphosate are threatening cotton crops. In the article "Loss of Glyphosate Efficacy: A Changing Weed Spectrum in Georgia Cotton," (Weed Science Volume 58, Issue 1, 73-79) Theodore Webster and Lynn Sosnoskie examine how the use of glyphosate-tolerant cotton (GTC) — created through genetic modification — has affected weed control issues since its introduction in 1997. The article is featured in the January/February issue of Weed Science, published by the Weed Science Society of America.


As farmers plant more acres of GTC, they are seeing a change in the most prevalent weeds, which now include varieties that tolerate or resist glyphosate. The two most troublesome weeds in Georgia cotton are Benghal dayflower, which is tolerant to glyphosate and many of the herbicides used in agronomic crops, and Palmer amaranth, which has developed resistance to many classes of herbicides including glyphosate. These weeds typically develop in systems without diverse weed control practices.
 
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