Burndown Questions

Author: Larry Steckel, Extension Weed Specialist 7 Comments

It finally looks like this long winter is coming to a close.  We will likely start putting out burndown applications this week.  We are well behind the burndown pace of most Tennessee springs where at least some would have burndown applications applied by this time.   However, this was not a typical winter and as such we are not behind with respect to weed maturity.

The winter Tennessee experienced is not unlike what happens in the Midwest.  They typically see high mortality rates of fall germinated horseweed (marestail).  In walking a few fields it appears this is the case for us as well this spring.  The bulk of the horseweed we will have to manage will be spring germinated.  New horseweed germination started about 2 weeks ago and I would expect that to continue over the next few weeks.  As such it should be easier to control with it being much smaller than what we typically spray this time of year. I discussed different burndown tactics in a Feb 18th Blog which all should work well on small horseweed.

Does a residual make sense this spring?  That depends on if a follow-up burndown is planned at planting, the expected planting date and what is the intended crop. If the expected planting date is 3 weeks or so off and the plan is to burndown with something at planting then a residual in with the burndown now is probably not warranted. However, if the intended planting date is more than 30 days away, then a residual can provide the advantage of not having a large grown up mess to have to plant into later this spring. If corn is the intended crop then a residual added to an early burndown often will not add much as most of the popular Pre and Post applied corn herbicides will also control newly emerged horseweed.

Leadoff is a popular residual option in an early burndown program. Leadoff is a premix of the SU herbicides rimsulfuron and thifensulfuron. It will provide several weeks of residual control of winter annual weeds and will help curtail regrowth of horseweed that has been injured by dicamba that otherwise might re-grow.  It also will aid in control of ryegrass and poa over glyphosate alone.

On the management side, do not expect Leadoff to control existing horseweed as it will need to be mixed with dicamba and glyphosate to do a thorough burndown of horseweed. Please note there is a 30 day plant back to cotton and soybean after a Leadoff application.  Under cool, wet and higher pH soils, some non-STS soybeans can have their early growth checked up some where Leadoff has been used. In corn it can be applied clear up to planting.

Valor, Sharpen and Verdict are the other popular residual herbicides typically used in an early burndown. Of course, Sharpen and Verdict will also do a good job on controlling existing horseweed. The main reason to utilize any residual herbicide in early March is for residual winter annual control.  Leadoff, Valor, Sharpen and Verdict will all provide about the same amount of residual control for winter annuals.  Please do not expect residual Palmer control from these applications. There is no residual herbicide that will typically provide any measurable Palmer amaranth control in soybeans or cotton when applied during most of the month of March.  Also we need to be more wary of Italian ryegrass this spring, which I will touch on in another blog.

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7 thoughts on “Burndown Questions

  1. Great article Larry. How well will Leadoff help out with summer annual grasses applied in a burndown situation for cotton or soybeans? For those that are not ALS resistant will this help us take some of the selection pressure off of Dual or RU that will likely go out PRE or early POST? If I remember correctly some of those ALS inhibitors have a long residual.

    1. Thanks Lucas

      Good question…Leadoff at 1.5 oz will provide about 30 days of residual control. For some of the grasses it may be a little better, but I would not expect alot more residual than that with spring applications.

  2. Larry, the biggest plus for Leadoff in my opinion is that it is not a ppo.
    I’m trying to rotate chemistry!!!
    I sprayed some acre’s back in Jan. they look pretty good now.

    1. Mike

      You make a good point on rotating chemistry. We need to keep rotating herbicides not only in crop but before planting as well.

      Thanks for the comment,

  3. How about mixing leadoff with Verdict or Sharpen to provide the complete Broadleaf burndown especially maretail or follow it at planting with Verdict on the earlier corn burndowns or when soybeans need their just prior to planting burndown when the the first pigweed flush happens since it will probably happen earlier this year.

    1. Greg

      I have not checked the label to see if Leadoff can mix with a Sharpen based product. Your comment makes good since, particularly now with all the Palmer that has emerged in Mid-March.


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