A post harvest burndown herbicide application can pay off with better weed control, saving you time and money next spring. Without burndown, weeds can take hold after harvest. And weeds that germinate during mild fall weather might mature enough to produce seeds, adding to the weed seed bank. Burndown plus residual weed control in late winter readies a clean seedbed for faster soil warming and better stand establishment next spring.
Close the Green Bridge
Winter annual broadleaf weeds such as henbit, purple deadnettle, common chickweed and marestail create green bridges that allows insects and diseases to survive from one season to the next. These weeds can overwinter, germinating in early spring. An effective solution is to apply herbicide tank mixtures that offer both burndown and residual activity.
Weather can delay or prevent burndown applications. Miss the application window, and preplant intervals will limit your herbicide choices. It also becomes much tougher to eliminate large-sized winter weeds, particularly henbit, which has become a major weed pest across the South. In addition to slowing soil warm-up and delaying planting, henbit can provide a green bridge for insect and nematode pests to carry over into the new crop. To close the green bridge and break the infestation cycles, entomologists recommend at least four consecutive weeks with no live weeds in the field before planting.
In the Delta, wild vetches, clovers, peas and henbit are possible green-bridge weeds. Louisiana State University entomologists and weed scientists have identified several pests that may infest crops via the green bridge, including thrips, aphids, bollworms, cutworms, spider mites and nematodes, as well as seedling diseases.
Control Marestail This Fall
Marestail (horseweed) is getting harder to stop once it gets away from growers in the spring. This is especially true when herbicides are applied outside the preferred window.
Population density of marestail has been increasing due to converging factors:
- Historical overreliance on one herbicide mode of action has led to glyphosate resistance.
- Cold, wet springs set up late flushes of marestail.
- More acres of no-till soybeans and wheat enable increased seed germination and survival.
- High-volume seed production per plant creates heavy weed pressure and seed dispersal. A single plant can produce more than 200,000 seeds, and the wind can spread them long distances.
Over most of the South, marestail is resistant to glyphosate and tolerant to paraquat, atrazine, ALS-inhibiting herbicides and diuron once it has progressed beyond the early seedling stage.
Some good news is that winter annual marestail is relatively easy to control with a fall application of a herbicide that has burndown and residual activity. Best results come from combinations of residual herbicides plus 2,4-D or dicamba when marestail is in the small rosette stage and less than 6 inches tall. For effective marestail control, we recommend using a tank mixture with more than one mode of action.
Preparing for Fall Burndown
Using the right product and optimum preplant intervals gives farmers more flexibility to switch crops during spring planting when weather or markets call for a change. The DuPont portfolio includes burndown plus residual herbicides that mix well with glyphosate, 2,4-D, dicamba or paraquat (Gramoxone).
For planting flexibility next spring, apply LeadOff® with glyphosate (before marestail emerges) or glyphosate plus 2,4-D or dicamba (for emerged marestail). LeadOff® uses two unique active ingredients that complement contact herbicides by boosting their activity.
LeadOff® adds residual control of marestail, annual bluegrass, henbit and other winter annual weeds, giving corn, cotton or soybeans a robust start. Corn may be planted immediately after LeadOff®, while cotton and soybeans may be planted 30 days after application.* An exception is east of U.S. Highway 231 in Florida and all of Georgia, where LeadOff® must be applied a minimum of 30 days preplant to corn and 45 days preplant to peanuts.
For fields going into soybeans, DuPont™ Canopy® EX herbicide offers burndown and long-lasting residual control to keep fields free of marestail, henbit1 and other winter annuals until planting, so you can plant as soon as field conditions permit.
For more information on fall weed control, talk with your local DuPont representative. Or visit southernfieldday.dupont.com to see videos showing product performance on some of the South’s toughest weed challenges.
1 Addition of at least 8 oz/A of 2,4-D LVE is required to control marestail and henbit.
* See product label for specific crop/pest combinations controlled or suppressed and additional rotational information.
Always read and follow all label directions and precautions for use when using any pesticide alone or in tank mix combinations.
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