In the Furrow
Managing Pigweed in 2008
By Will Duffie County Extension Coordinator

Managing pigweed (Palmer Amaranth) just got a little more serious in Burke County. Back on June 20 of this year I reported on an issue that farmers were having a difficult time killing pigweed with glyphosate in several fields in our county. This is not too surprising because during the summers of 2005 and 2006, farmers in 11 counties in Central Georgia began fighting pigweeds resistant to glyphosate. Farmers in all other counties in Georgia are hoping to delay the arrival of this seed on their farms.

The three fields that we thought to have suspect pigweed were monitored and then seeds were collected in the late fall. The seeds were taken to the laboratory at the UGA Coastal Plain Experiment Station in Tifton for evaluation. After the seeds were chilled for three weeks, they were planted in pots and grown in the greenhouse. Once plants emerged, plants were treated with glyphosate herbicide at rates ranging from 1.5 times to six times the standard rate. The results from the three fields in Burke County show a high resistance to all rates applied. What this translates to is that these populations of pigweed cannot be controlled with glyphosate in the field.

Burke County is not the only county to have pigweed (Palmer Amaranth) confirmed resistant to glyphosate in 2007. Wheeler County is positive and seed from a number of other counties are currently being evaluated in the greenhouse.

Dr. Stanley Culpepper and Dr. Eric Prostko, UGA Extension Weed Scientist, have developed herbicide programs to manage this weed in cotton, corn, soybean, and peanuts. Information will be distributed during the winter production meetings.

For more information contact the Burke County Extension Office at 706-554-2119.