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Planting season is right around the corner and there is a LOT left to do before the seed goes in the ground. For many operations, a major task that has yet to be completed is an early burndown. In many areas, extensive rainfall has left sprayers sitting idle for several weeks. Now the question many farmers find themselves asking is, “what burndown can I spray to control all of the winter annuals that have flushed in the fields?”
One thing to consider when making this decision is temperature. Ideally, we want warm (55°or higher) temperatures for multiple days in a row to help speed up herbicide activity. The second thing to consider is the plant back interval for the crop you plan to plant in that field. Lastly, make sure to consider which winter weeds you are targeting and what herbicides they may already be resistant to (specifically talking about marestail).
Herbicide efficacy is greatly influenced by humidity, sunlight, and temperature. In many cases, the greatest limiting factor we deal with in a burndown scenarios is temperature. The primary herbicides used in these situations are glyphosate, 2,4-D and dicamba, all of which are systemic herbicides. When the air temperature falls below 60° F, the absorption of these herbicides is reduced and subsequently, the efficacy is then also reduced. Therefore, it’s important to use higher labeled rates than typically used during the season.
Plant Back Restrictions:
Plant back intervals is another very important detail that is sometimes overlooked. For example, 2,4-D is often used to kill marestail early in the year and, depending on the rate used, this herbicide could carry a 7-day plant back to corn or a 10 to 14-day plant back window with soybeans. The University of Arkansas created a very helpful document that can serve as quick reference if needed, which you can access here.
A final topic to consider when planning your burndown is the weed spectrum in the field. In most cases, you’ll probably see a mixture of chicweed, henbit/deadnettle (they’re hard to tell apart), hairy buttercup, cressleaf groundsel and marestail. Most of these are fairly easy to control with glyphosate, but marestail can be troublesome. A high percentage of the native population we deal with has resistance to multiple modes of action, specifically glyphosate and ALS’s (FirstRate®). That is why it’s a good idea to include a Group 4 herbicide like dicamba or 2,4-D to help with control. Other herbicide options that are growing in popularity are Sharpen® or Verdict® and, depending on the rate used (≤1oz. or ≤5 oz., respectively), soybeans can be planted back immediately. This last option will also offer some added residual control of small seeded broadleaves and some grasses.
If you have any questions regarding your early-season burndown or chemical program in general, please contact your local Beck’s representative for a consultation.
Austin Scott | Field Agronomist & Herbicide Specialist
FirstRate® is a registered trademark of Dow AgroSciences. Sharpen® and Verdict® are registered trademarks of BASF.