A Fall Herbicide Application Can Help Control Winter Annual Weeds


Do you typically make a fall herbicide application following harvest? Are you considering one this year?

fall herbicide application

Here are a few reasons to think about weed control after harvest and consider making a fall herbicide application:

  1. Treating winter annual weeds in the fall following harvest, and before the ground freezes, is a reliable way to control many weeds.

  2. Fall treatments can also be less expensive and, oftentimes, deliver better weed control than spring-applied herbicides.

  3. A different mode of action can possibly be added to avoid herbicide resistance with fall applications. Herbicide resistance of several winter annual weeds is a problem in many states.

  4. The risk of off target drift is less of an issue because there are no actively growing crops with fall applications.

  5. If a long residual herbicide is fall applied to extend the length of weed control, annual spring-emerging weeds can sometimes be controlled into mid-May. That could lead to more timely planting next spring with reduced weed competition and savings from less spring-applied herbicide needs.

  6. There are many herbicides to select from for winter annual weed control. If you choose a residual herbicide, be sure to adhere to any planting restrictions that apply to next year’s crop.

Read This Next: Everything you need to know to make your farm’s chem applications successful—whatever you spray, whenever you spray it. 

Field Pennycress weed control Field Pennycress

If you’re unsure about a fall herbicide application, here are few ways you can work around those concerns and better control winter annual weeds:

1. Concerned that you don’t have enough time or labor available to get spraying done while harvest is in progress?

There are usually times during a harvest delay that would offer a window to apply herbicides. Even hiring a commercial sprayer can be cost effective in most situations, and spring herbicide applications still require time and labor. Planting is the most important trip across field and the right timing is important then, too.

2. Not sure you have enough cash flow remaining for the current year?

Remember that the price of the chemicals chosen for next spring could be higher compared to fall-applied herbicides. Oftentimes, you’ll also wind up with less efficient weed control with a spring herbicide application due to the size of the overwintering weeds.

Start by identifying the weeds.

As harvest is winding down, think back to any weeds present in soybeans and corn fields. And remember that if you are no-till farming you may see an increase in winter annual weeds.

Are the weeds winter annuals?

Common winter annuals include Marestail, Henbit, Tansymustard, Downy Brome, Field Pennycress, Annual Ryegrass and Shepherd’s Purse. Winter annual seeds germinate in early fall into December. Dandelion is a perennial weed but often found in fall row crop fields. The broadleaf species generally form a rosette to overwinter. They will flower and produce seed by late June to complete the life cycle.

Downy Brome weed controlDowny Brome
Shepherd's Purse rosette weed controlShepherd's Purse rosette
Tansymustard weed control Tanymustard

All of these weeds have troublesome symptoms in common and can impact the following year’s crop yield. They all have the potential to: 

  • Rob the soil of nutrients and water
  • Delay soil warming in the spring
  • Cuse issues with planting equipment operating correctly

Overall, treating problem weeds in the fall prior to the soil freezing is simply good stewardship and smart farming in several ways.

Always be sure to read and follow label use instructions for any chemical application you make.

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