As we progress steadily through the 2017 growing season and look forward to harvest time we need to reflect on the challenges we faced during the spring while planting. One of the issues we face more and more every year is what to do with the winter annual weeds that seem to get worse as we move more to reduced tillage systems. Looking back at this past spring, many growers were faced with the question of what to do with these weed issues.

Winter annual weeds are those weeds that germinate in the fall and finish their lifecycle the next spring or summer. Three broadleaf weeds come to mind that fit this cycle in Iowa. These include: Marestail (Horseweed), Henbit and Chickweed. For now, we will keep from talking about winter annual grasses even though they can be an issue in areas but not as prevalent of a problem as the aforementioned broadleaves. 

So, what do we do?

There are many options that come to mind for fall herbicide applications, but we want to keep this practice simple. Crop protection companies have many herbicides labeled for fall application, but the best options are of the growth regulator (auxin) class of herbicides. These are better known as 2,4-D or Dicamba products. There are other good options as well but these two are the base of a good recommendation. 

Timing

Timing of fall applications can be limited for a couple of reasons. First, you need to let the weeds recover after harvesting the field so they can "take in" the herbicide and secondly, you need to spray the weeds prior to a killing freeze. Keep in mind that control of these weeds is easier when they are small.  This makes the time for application short and while growers are harvesting this can be a difficult assignment.  Your local FS retailer can help get this application done timely it just takes good communication. 

Planning

Think about your fields this past spring that were infested with winter annuals and became a challenge while planting. Talk with your local FS crop specialist about a burndown on these fields and the timing of harvest for when might be a good time for application.

The Benefit

Controlling hard to control winter annuals this fall will benefit growers in many ways next spring. These benefits include: cleaner fields during the growing season, more effective, normal and timely spring herbicide applications, less early season insect pressure, faster soil warming, easier planting operations, and less weed competition for nutrients. 

Fighting Chickweed and Henbit during planting can be difficult and trying to kill Marestail in the spring and summer can be a big challenge as well. These weeds can be prolific and are known to be very competitive with a young growing crop.

James Russmann serves the FS system as GROWMARK senior crop protection territory manager. He can be reached at [email protected].