What is in this article?:
- For less soybean injury, run planter after spray rig
- Let planter chase spray rig
- Burndown window is expanding
- Cover crops a weed control option
Making a herbicide application after the planter has already gone through the field often involves “a very narrow window of opportunity, especially when temperatures are warm,” says Tom Eubank, assistant Extension and research professor at the Delta Research and Extension Center, Stoneville, Miss. “The approach I advocate is for the planter to chase the sprayer, and where farmers used this approach last year, they didn’t have nearly the injury issues we saw when we were making an application behind the planter."
BILL LONG, from left, DuPont Company, Greenwood, Miss.; Bob Stonestreet, Clarksdale, Miss., consultant; and Tucker Miller, Miller Entomological Service, Drew, Miss., were among those attending the annual conference of the Mississippi Agricultural Consultants Association.
Burndown window is expanding
The burndown window for many growers, he says, “has now become from January to planting season. In some cases, we’re applying two burndown treatments — one early season to control winter weeds, and a second prior to planting to control pigweeds and other emerging weeds.
“We’re using a lot of paraquat/metribuzin combinations in soybeans that not only clean up some of the escapes that may have got by the glyphosate/2,4-D early on, but also control pigweeds that may be popping up.”
Liberty is a good option on horseweed, particularly near planting, Eubank says. “We have research that shows if you don’t control horseweed prior to planting corn, cotton, or soybean, it can adversely affect yield. In every scenario where we applied Liberty at planting, we got a yield increase.
“Liberty is expensive, but if you get into a salvage situation where you need to control horseweed, it does a good job. You can combine it with metribuzin for synergy, but again it’s important to have adequate water volume and coverage for the Liberty to work properly. And you also need warmer temperatures and sunlight.
“Research has shown that from about 10 a.m. until about dusk is the best time to apply Liberty. Standard advice has been that the best time to spray is early morning in order to get good coverage and limit drift. But, Liberty efficacy goes down the earlier in the morning you apply it — as much as 20 percent to 30 percent reduction in control. Heat and photosynthetic activity are important with this product.”
A glyphosate plus FirstRate combination is another good option for horseweed, Eubank says. “Typically, I’d rather see this go out in-crop, when horseweeds and soybeans are already up. This doesn’t really kill the horseweed — it basically shuts down the growing point, and the plant just sits there for a long period of time, allowing the beans to canopy and shade out the weed.”
Although some growers have used Resource, he says it is not effective on horseweed, nor is paraquat alone. And not all of the ALS-inhibitor herbicides are effective. While FirstRate and Envoke have good activity, he says, for Leadoff, First Shot, Harmony, “horseweed has to be really, really small for them to work effectively.”