Georgia has the world's first population of Palmer amaranth — commonly known as pigweed — resistant to glyphosate. This will cause problems for cotton farmers, says a University of Georgia (UGA) weed specialist.

Right now, glyphosate-resistant Palmer amaranth is known to infest about 500 acres of cotton in central Georgia. Stanley Culpepper, a UGA Cooperative Extension weed scientist studying the outbreak, says seeds from at least 100 fields in the area have been harvested to determine any further distribution.

It's a wicked weed. “This could be a real threat to future cotton production in our region,” he says. Pigweed can quickly grow more than 8 ft. tall with a thick stalk and suck valuable nutrients from nearby plants. It can clog a cotton picker, too, making it hard to harvest the crop.

In 1997, farmers started planting cotton that was developed to stay healthy when sprayed with Roundup. In 2005, 94% of Georgia's 1.21 million acres of cotton this year is Roundup Ready.