By Larry Steckel
As corn harvest gets rolling it is apparent there was a heavy flush of Palmer that emerged several weeks ago. After the rain last week there will likely be even more emerge. Though no one wants to spend more money on drought-stressed corn post harvest it well could pay off next spring in soybean or cotton. Good options to control this late flush of Palmer include tillage and the burndown herbicide Gramoxone (paraquat).
Please note if you elect to go with tillage that a disking will likely provide good control of smaller Palmer less than 4 inches tall but larger Palmer, more than 8 inches tall, will often re-root and grow back. Likewise, Gramoxone will provide consistent control of smaller Palmer but regrowth can happen with larger plants. Residual herbicides should be considered as well since we have so much growing season left. Fall applied residual products like Valor, metribuzin and simazine would all be good choices here, depending upon what crop to be planted next spring.
A newer herbicide Sharpen would also fit into a fall program. It can be used at rates up to 2 ounces per acre in the fall before corn, grain sorghum and soybean.
If the field is slated to go to wheat this fall, then be cautious on utilizing a residual herbicide. Valor at 1.5 to 2 ounce per acre may be applied up to 30 days before wheat planting and would be viable option for residual control prior to planting wheat. Another option, particularly as we get closer to wheat planting, is Sharpen at 1 to 2 fluid ounce per acre, which can be applied right up to the pre-emerge timing.
Larry Steckel is the weed specialist with the University of Tennessee Extension.