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This is a good year to have more than one option for taking down weeds.

Tom J Bechman 1, Editor, Indiana Prairie Farmer

February 11, 2022

3 Min Read
giant ragweed growing amongst crops
ROLLING THE DICE: Here’s what might result in 2022 without a sound herbicide plan. Most residuals aren’t strong against giant ragweed, especially if spot pressure is heavy. Tom J. Bechman

Controlling weeds in a normal year is tough enough. You must track which herbicide-tolerant traits each soybean variety possesses. Then you must understand which herbicides may no longer be effective on certain weeds due to resistance issues. Throw in tight supplies of two major herbicides — glyphosate (Roundup) and glufosinate (Liberty) — and this could be a gut-wrenching year.

Jeff Nagel, a longtime agronomist for Ceres Solutions based in Lafayette and an Indiana certified crop adviser, believes you can mitigate potential stress by thinking through options before spraying season starts.

Here’s a hypothetical example and how Nagel would approach it if asked for advice: Suppose you battle marestail and waterhemp, plus giant ragweed in some fields. You have a lineup of soybean varieties with varying herbicide tolerance, including the main platforms on the market. Your supplier says he can get you some glyphosate and some glufosinate, but probably not all you want of either one. You haven’t sprayed glufosinate before.

Here is how Nagel would approach this situation based on various soybean traits.

XtendFlex. Option 1 — use dicamba, either Engenia, XtendiMax or Tavium for broadleaf weeds. Use your glyphosate to tank-mix with dicamba. The June 20 cutoff date for dicamba applies in 2022. Spray postemergence applications prior to June 20 and layer in a Group 15 herbicide like Dual Magnum, Warrant or Zidua SC for residual control of pigweeds as needed. If dicamba fields are in a sensitive area, drop dicamba and address those fields with glufosinate.

Option 2 — use your glufosinate supply for general post applications. Add the Group 15 for in-season residual, if needed. If grasses are heavy or bigger, tank-mix a Group 1 post grass herbicide like clethodim (Select) or fluazifop (Fusilade).

Enlist E3. Option 1 — use your glufosinate for general post applications. Add the Group 15 for in-season residual, if needed. If grasses are heavy or taller, tank-mix a Group 1 post grass herbicide like clethodim or fluazifop. A tankmix of glufosinate and Enlist One is very effective on waterhemp.

Option 2 — use Enlist One and your glyphosate for post applications. Add the Group 15 for in-season residual, if needed.

LibertyLink GT27. Use your glufosinate supply for general post applications. Add the Group 15 for in-season residual, if needed. If grasses justify it, add a Group 1 post grass herbicide like clethodim or fluazifop. If you don’t have enough glufosinate, your only other choices postemergence on giant ragweed and waterhemp are the Group 14 herbicides like Flexstar and Cobra.

Other options

With higher glyphosate prices, some are considering dropping glyphosate and tank-mixing a Group 1 herbicide like clethodim with dicamba or Enlist One for grass control. That’s an option, but there is antagonism between the growth regulator and post grass herbicides. Either increase post grass rates by at least one-third or apply separately.

Don’t forget glyphosate still helps on broadleaf weeds and improves overall weed control when tank-mixed with dicamba or Enlist One.

Be sure to optimize your post spray coverage. Herbicide supply for resprays will be limited. Do your best to do it right the first time. Pay attention to spray volume, nozzle selection, adjuvant packages and timely post applications for each product.

About the Author(s)

Tom J Bechman 1

Editor, Indiana Prairie Farmer

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