Manage Weeds Up Front

Treat Early, Use Residuals To Control Resistant Weeds

BELLEVILLE, ILL.
   In many cases nowadays, the weeds are winning, according to Dr. BryanYoung, Southern Illinois University Professor of Weed Science. Young spoke at the Belleville Research Center Field Day recently.
   “The southern third, perhaps the southern half of Illinois, I would anticipate as big a failure with glyphosate trying to control waterhemp this year as what we’ve seen with glyphosate not controlling marestail in other years,” Young said after showing a slide of a field on the Illinois side of the River near Cape Girardeau where a farmer planted beans in a field of waterhemp.
   As far as herbicides, Young finds there’s no guarantee. The University of Illinois as well as Young himself have confirmed glyphosate resistant horseweed (aka marestail) in the state, as well as common waterhemp. Glyphosate resistant waterhemp has been confirmed in several sites in Jackson County, and that involves a number of acres, but there are other sites affected but at a low frequency. Giant ragweed is also becoming a problem, and Young expects that to be the next resistant weed in the state. He urged farmers to be on the lookout for resistance in any of these.
   “Buying a herbicide program is not a ticket for season long weed control,” he said. “Alot of service and guarantees may be suggested, but they might not be able to fix your problem once you have a problem because we’ve lost flexibility if you have weeds resistant to glyphosate. There is no season long weed control.
   “I can’t guarantee anything if I’m talking to you in the month of March,” he continued. “If I’m talking to you in the month of July and you have no weeds, I can guarantee weed control; but beyond that I don’t have that much control and I don’t have that much faith in the weeds you might have in your field.”
   It may take $50 an acre to control weeds in soybeans. However, there are a few proactive measures farmers can take to help prevent problems.
   “Once you get resistance to glyphosate you’ve lost your flexibility in the application timing, the post-emergence timing, so we need to be able to manage our weeds better in a timely fashion,”Young said. “The only way we can do that probably is through the use of residual herbicides which widen the application window so that we can prevent a hairy nightmare out in our field if we’re rained out. We need to manage the weeds when they are still less than six inches or even less than four inches. That’s the stage where we can manage them effectively with some of these alternatives to glyphosate.
   “So we just need to be very proactive and manage the weeds up front, then hopefully later in the season it won’t be as difficult,” he added. “Rescue treatments when you have glyphosate resistance are extremely difficult, because glyphosate has been our rescue and we just don’t have that available as a rescue anymore in fields infested with glyphosate-resistant weeds.” Δ
   BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower 

Dr. Bryan Young, Southern Illinois University Professor of Weed Science, anticipated a big failure with glyphosate trying to control waterhemp this year. Photo by John LaRose Jr.