With peanut production costs rising, yellow herbicides could be a bargain for Texas producers in 2008, according to a Texas Extension agronomist.
“One of the most frequently asked questions I get is about tolerance levels of peanuts to yellow herbicides,” said Todd Baughman during a recent peanut grower meeting in Littlefield.
“The keys for yellow herbicide use in peanuts are rate and method of incorporation,” Baughman said. Several herbicides are available, including Prowl EC, Sonolan, and Prowl H2O. “We have a lot of data on weed spectrum and peanut tolerance. Applied properly, we’ve seen no problems with tolerance. And we see benefits in weed control, especially for tumbleweed and careless weed.”
Baughman said with increasing potential for herbicide resistance, adding yellow herbicides to peanut weed control strategies makes sense. “Resistance has not been a problem so far and use of yellow herbicides may be a big reason, especially with careless weed.”
A key for 2008 weed control is to do everything possible to control weeds early. “Start clean,” he said. He also recommended taking care of winter weeds before planting, when an inexpensive contact material will be effective. Weeds such as marestail can be taken out early. “If you get them now, you may not need a later application.”
He said contact pre-emergence materials, such as Gramoxone Inteon can be “very effective on Russian thistle (tumbleweed). Other contact products have been “hit and miss.”
Tank mixes such as Gramoxone and Dual Magnum may improve control, Baughman said. Gramoxone provides good contact control and Dual Magnum adds residual activity.
Applying Dual Magnum pre-emergence during cool, rainy periods could set peanuts back a bit.
He also cautioned about delayed application with the Gramoxone and Dual Magnum tank mix, after cracking. “As we move along the timeline after cracking we begin to see more injury. At more than 28 days after cracking, we may see significant injury.”
He also explained that cracking means when the peanut plant pushes up the soil, “before significant vegetation shows.”
He said in some cases this tank mix would result in early burn injury “but no yield loss has been evident.”
Growers who plant late, as late as July 4, and try to push the crop, could see some herbicide injury.
He said Dual Magnum provides good yellow nutsedge control. “Valor has not been used as much in Texas as in other states but may be a good option for morningglory. “We’ve seen some injury and we can’t pinpoint when injury will occur.”
Baughman said Cobra has a new label for peanuts. “It’s a good broad spectrum herbicide.”
Application should be made when the peanut has at least six true leaves and should not be applied within 90 days of harvest. “Cobra can produce significant burn on the leaves. In recent tests in Georgia and Texas, only one instance of yield loss showed up in a Cobra plot. With two applications the mid-season application will show a little more burn.
He said from a weed control standpoint, size counts. By controlling careless weed early, at two inches or less, success rate of Cobra is 90 percent. That drops to 60 percent with three- to four-inch tall weeds and 20 percent at 6 inches.
“We have to be early, Cobra is not a rescue treatment,” Baughman said.
He said studies on Basagran as a safener with Cobra have shown the combination provided no safening benefit and in some cases resulted in increased careless weed survival. “Stay away from that combination.”
Baughman said growers should do a pre-plant checklist on weed control strategies that includes:
· Know the weeds.
· Know herbicide options. Know what each one will and will not do.
· Yellow herbicides provide a good foundation and are important tools in peanut weed control programs.
· Start off clean.
· Be aware of rotation restrictions.
· Apply herbicides on time.
· Scout the crop for unusual weeds.
· Weed control in peanuts starts in the fall.