Pesticide Resistant Weeds Could Be Problem

November 17, 2009 Updated: November 17, 2009

No, this isn’t some 1950s horror movie about mutant weeds from outer space. However, to the average farmer, pesticide-resistant weeds can be just as scary.

Particularly in southern states such as Georgia and Alabama, the pesticide-resistant pigweed has become a very serious and costly problem within the last year.

Amaranthus palmeri or Palmer pigweed as it is commonly known, prefers the warm climate of the southern region of North America and can be found in many soybean and cotton fields of the deep south. This flowering plant grows as much as an inch per day and is notorious for its ability to overtake cropland.

“The problem is spreading at an alarming rate and many producers did not realize they had a problem until they were well into the cropping season this year,” said Dr. Jason Norsworthy, weed scientist at the University of Arkansas, Division of Agriculture in an e-mail.

Normally, southern farmers use a commercial herbicide called Roundup to control weeds and intrusive plants. Since the early 1990s Roundup and has been so effective at controlling unwanted weeds that scientists have genetically engineered cotton and soybeans to resist the pesticide so farmers could easily apply it without fear of damaging the crops.

But now farmers have been forced to return to the age-old method of removing weeds by hand, a process almost unheard in modern agriculture. The labor required for this weed control method can be expensive, but it’s the only choice some farmers have to compete in the market.

As a result, it is estimated that southern farmers battling pigweed now spend three times as much for pest control and only get back a third of the harvest.

GM Watch, a non-profit organization, says that in Arkansas nearly 750,000 acres of farmland are now infested with pigweed. Another 500,000 acres are infected in Tennessee, and the Mississippi River area is most damaged by the aggressive plant.

Weed scientists like Dr. Norsworthy have been working on a glyphosate-resistant pigweed for about four years, since the first resistant field was found in 2005, but the plant has proven to be a challenging pest.

“We are diligently looking for solutions, but we have had limited success in developing programs to this point, especially in cotton,” Dr. Norsworthy said.