On a recent hot and sweltering Delta day, cotton producer Johnny Larson grabbed a 3-foot log, held it over his head and threatened to beat the living stew out of a glyphosate-resistant pigweed pulled from a nearby cotton field. The threat was in jest, but it revealed a sentiment in Larson that his battle with pigweed was becoming personal.
Larson farms 1,700 acres of cotton, 1,100 acres of corn, 800 acres of soybeans, and 420 acres of wheat and deals with more resistant weeds that he cares to think about. Weed control has gone from tough to easy to tough again for the Friars Point, Miss., producer. This time around, it’s probably going to stay tough for a while.
“Farming was so easy with the Roundup Ready system,” Larson said. “It was so simple to farm. Now we’ve had to go back to the old ways, tilling and using products that can hurt the cotton. But that’s what we have to do. I may hurt the cotton, but my better yields are where I can keep the field clean.”
Larson first noticed escapes in the Roundup Ready system in 2009. “We started seeing some ryegrass and a few pigweed escapes. Last year, we knew we had a resistance problem. But we had no idea. One pigweed plant produces so many seeds. The way they can reproduce is like a sci-fi movie.”
Although Larson used residual herbicides in cotton in 2010, it didn’t take him long to realize that his weed control program needed more punch.
Today, Larson’s tools for controlling glyphosate-resistant pigweed include planting a majority of his crop in glufosinate-tolerate cotton varieties, residual herbicides, chopping crews and a 12-row, 915 Willmar Hooded Sprayer with directed spray capability.
In February-March, Larson made a preplant application of Reflex, then planted about 1,200 acres in glufosinate-tolerant varieties on fields that that had pigweed problems in 2010. The rest was planted in Roundup Ready varieties. Cotton varieties include PHY 375 WRF, PHY 367 WRF, DP 0912 B2RF, DP 5458 B2RF.
Larson says choice of weed control technology is now just as important as varietal selection in the presence of glyphosate-resistant pigweed. “If you have any degree of weed pressure, it’s unbelievable how that will kill you.”
On Roundup Ready cotton, Larson made an over-the-top application of Sequence, while applying Ignite over-the-top of glufosinate-tolerant cotton. By mid-July this season, Larson had made two applications of Ignite and was in the process of putting on a third. “If I have some more little enemies coming up, I’ll put out a fourth.”
Larson said that his glufosinate-tolerant varieties were his best-yielders in 2010, one reason why he’s planted most of his farm in them this season. It’s the technology’s ability to keep fields clean “and kill a little bigger weed than glyphosate” that is responsible for the higher yields, he believes.
While it would be difficult to throw a rock into a Mid-South cotton field without hitting someone with a hoe in his hand this season, there have nonetheless been plenty of glyphosate-resistant pigweed escapes. Larson says hand chopping has its weaknesses, too. “When the weeds get to a certain stage, you can chop them down and they won’t come back. But practically speaking, when it’s 100 degrees outside and they’re chopping with a hoe made in China, you’re going to end up going back through at least one more time. But I don’t mind giving them the work at the price of cotton today, and they need the money a lot worse than I do.”
When cotton gets bigger, Larson will shift to his 12-row, Willmar 915 Hooded Sprayer. The sprayer “is far superior to other hoods we had before. If I had a farm and I didn’t have Ignite, and I was going to raise cotton, I’d have plenty of hoods. It is not going to get pigweeds in the drill. But hopefully, you’re covering three-fourths of the row under the hood.”
On glufosinate-resistant cotton, Larson will go with Gramoxone, Ad-Spray and Direx under the hoods, and may use Ignite in a directed spray. On glyphosate-resistant cotton, he’ll go with Gramoxone and Direx under the hoods and glyphosate and Cotoran in a directed spray.
At layby, he’ll make another hooded sprayer application. “Sometimes, I may leave Gramoxone out. But sometimes, you have to throw everything you can at it.”
Tennessee Extension cotton specialist Larry Steckel says the 915 hoods are designed for the application of a contact herbicide. “They are open at the end, longer and have three nozzles. I’ve had good luck killing a 2-foot to 3-foot pigweed with it.”
According to Nathan Duff with Willmar, the new hood design combines elements from older generations of hoods. “It has an open front, but it’s still more sloped and longer so it can run through taller cotton without damaging it. The nozzles are in staggered planes so the weed gets three shots as it goes through. The hoods are also designed to run on the ground, with metal skids on the bottom.”
Larson said the glyphosate-resistant weeds have increased his weed control budget by at least 30 percent, but he credits his local Helena retailer with going an extra mile to keep costs under control.
When asked what he thought of the most hard-to-kill weed in the America today, Larson said, “Have you looked at the highways? They’re everywhere. Until they come out with a chemical that will take care of it, we’ll be doing this until the Lord comes back, or the cows come home, or whatever. It’s like a sci-fi, horror movie.”