Plant-back Restrictions. The table below shows the currently labeled plant-back restrictions for burndown products in cotton. If wet weather continues and applications are delayed even further, then planting could also be delayed depending on which burndown herbicides are chosen. Pay close attention to the plant-back restrictions on the label.
- Weed Species Present. Paraquat and glyphosate have no plant-back restrictions. While they are the backbone of most burndown programs, they are only fair to poor on some winter weeds. Some tank mixes may be required for adequate control. Know your weed species.
Weed species not adequately controlled by glyphosate alone include Carolina geranium, curly dock, henbit, cutleaf eveningprimrose, and smartweed spp. Weeds not adequately controlled by paraquat alone include curly dock, cutleaf eveningprimrose, marestail, smartweed spp., and swinecress.
Tank mixes with Goal, Clarity, Valor, 2,4-D, and Aim will be needed in many fields for adequate control. Weed size is important with Aim and Valor. Weeds taller than 4 inches or with 3-inch rosettes are not controlled well. Therefore, pay close attention to the targeted weed species, weed size, and then the plant-back restrictions for various tank mixes.
For photos of troublesome burndown weeds, see the LSU AgCenter’s burndown herbicide guide on the web and a list of weed pictures at http://www.agctr.lsu.edu/cotton/WeedControl.htm
- Acceptable Planting Dates. The window for planting cotton in Louisiana is generally from April 15 through the end of May. Historically, yields have declined when cotton is planted after May 15. The overall yield decline that can be expected with late-planted cotton is different in every year and depends on the growing season.
The main point is that all cotton does not need to be planted by May 1 or even May 5. It is more important to burn down cotton land properly, control cutworms adequately, and plant in good conditions than to do a poor job of burndown and/or violate the plant-back restrictions, risking injury.
The wet weather has the potential to delay burndown and planting in some fields, but getting the crop off to a good start takes precedence over rushing burndown and planting by the end of April./li>
- Burndown By Air. In wet conditions, applying burndown herbicides by air may be the best option. Most burndown herbicides are more effective, however, when applied with ground equipment.
|Product||Days to Planting|
* Consult label of individual products
** An accumulation of 1 inch of rainfall or irrigation is required
Sandy Stewart is an assistant professor and cotton specialist; Steve Kelly is an assistant professor and weed specialist and Roy Vidrine is a professor of Weed Science at the LSU AgCenter.