Staggering Southern Weed Resistance
The gentleman in this photo with Palmer pigweed is at least six feet tall.
At the Weed Science Society of America meeting last week in Florida, university researchers provided an update on the state of glyphosate weed resistance in the south. Southern producers already face one of the most challenging and devastating weeds, Palmer pigweed. In 2008, the extent of glyphosate resistance increased exponentially.
This past year, researchers in Tennessee found Palmer populations that withstood 152 oz/A of glyphosate and still survived. Before recently, only Georgia had populations with such high levels of resistance.
- Tennessee: 10 counties confirmed with glyphosate-resistant Palmer pigweed, one county with glyphosate-resistant waterhemp
- Arkansas: At least 18 counties with confirmed glyphosate-resistant Palmer pigweed, likely many more
- Mississippi: Two counties with glyphosate-resistant Palmer pigweed
- Louisiana: A couple fields are being studied for potentially glyphosate-resistant Palmer pigweed. In general, waterhemp is a bigger problem.
One of the roadblocks to controlling Palmer pigweed has to do with the nature of the growing season in this part of the U.S. Since corn is harvested at the beginning of August, from that time until freeze, there is a lot of time for Palmer pigweed to germinate before the first freeze. For a weed that can produce 500,000 seeds per plant, the potential damage that can occur in this time period is staggering.
Additional weed costs have increased $30 to $50 an acre. In addition, the threat to conservation tillage systems is very evident as so many chemical control measures have failed to produce adequate results. Tillage has been seen in places for growers who have no other options.
How severe of a problem is Palmer pigweed in your fields? Have you seen your weed management costs increase? What strategies have you adopted to help reduce the problem? What factors have impacted your costs?