A US weed scientist says that weed resistance to glyphosate herbicide, used widely on genetically modified Roundup Ready cotton and other crops, has the potential to be a major problem for US cotton farmers.
North Carolina State weed scientist Alan York said that until now, herbicide resistance
has been dealt with simply by switching to an herbicide with a different mode of action. But now, he says, there are no new effective herbicides. Glyphosate-resistant horseweed
has been widely reported in the Cotton Belt, and York said the University of Georgia
discovery of glyphosate-resistant Palmer amaranth has caused a much higher level of concern.
In tests at the University of Georgia, a 4X rate of glyphosate, applied three times
had little negative affect on Palmer Amaranth. “If you grow cotton in the Southeast, and you have Palmer amaranth in your fields, looking at side-by-side comparisons of resistant and non-resistant pigweed should scare you to death,” York says.
(SOURCE: Southeast Farm Press)