By Brian Hefty

If you are raising a crop that will be harvested in the summer or early fall, a post-harvest burndown is often essential.  The big question each year is which herbicide program should you use?  We all know that by avoiding tillage as much as possible, you can reduce erosion, conserve moisture, and build soil organic matter and soil structure.  That’s why herbicides are so important.  Here are the top products we suggest you consider, as well as the products we usually avoid when making agronomic recommendations for burndown.

PRODUCTS WE TYPICALLY RECOMMEND:

  1. Roundup.  I know there are lots of resistant weeds out there, but let’s face it – Roundup still kills 95% of weed species on most farms.  For $2 to $4 per acre, it makes a nice tankmix partner.
  2. Distinct.  If you use the 2 oz rate, you’re only talking around $4 per acre.  Yes, there is a trace of dicamba in there, but the main weed killer is diflufenzopyr, which we love.  Distinct is simply Status without the corn safener for a much lower price.
  3. Valor.  Valor may not be perfect either as a burndown or as a residual herbicide, but it’s inexpensive, can be used in front of many different crops, and has good activity on many of the Roundup-resistant weeds.
  4. Sharpen.  While Sharpen is more expensive than Valor with less residual, its burndown activity is better and faster.

PRODUCTS WE TRY TO AVOID:

  1. Atrazine.  We don’t like the carryover risk or the environmental concerns.  You and I both know that atrazine has the same LD50 as table salt, but most city people think it’s terribly dangerous.  Since atrazine can leach, every farmer needs to be careful about when and where they use atrazine.
  2. Long-lasting herbicides.  This includes Pursuit, Ally, Tordon, Milestone, and a handful of others.  You may know what you want to plant this fall or next spring, but all of these products have the potential to last beyond next year.  Use great caution with long-residual herbicides.
  3. 2,4-D and straight dicamba.  You can certainly use 2,4-D and dicamba if you want to.  They are both pretty effective on a lot of weeds in burndown, and they leave your rotation options fairly open.  The big concern we have is spray drift.  I’d rather have you use Distinct.  You’ll have less drift risk and better weed control for similar money.  For a late fall burndown when drift is no longer a big risk, we have used extremely high rates of 2,4-D or dicamba to control marestail and other winter annuals with great success.  If you want, you can do the same with the 6 oz rate of Distinct.

Additional burndown tips include waiting for some regrowth on weeds before spraying, making your application when the weather is relatively warm (above 70 degrees), using the correct spray adjuvants (usually AMS and crop oil or NIS), and getting good spray coverage.