Learn from Your Weed Challenges

As we approach harvest this year, it’s a good time to reflect on what happened during the season. It was an extremely trying year for planting and for implementing a successful weed control program.

As I drive past fields up and down the state, there are many weed control failures still affecting our fields moving into harvest. Most of the weed problems I notice are giant ragweed, waterhemp and marestail. Growers need to consider mapping and recording each field individually, identifying the weeds that are present and problematic. Doing this will help set them up for a more successful 2018 season. Some of these fields have been sprayed 3 times this year, including using a residual, and even after that intense weed control effort weeds are still present in the fields. Moving into 2018, remember each weed has varying life cycles and needs to be addressed individually.

Marestail can germinate when soil temperatures are as low as 50 degrees, therefore it can still, and will, germinate in the fall. When this happens, it becomes extremely difficult to control in the spring. A good fall burndown, including a residual, is a good management practice. This holds true for dandelions also, as they are difficult to control in the spring since they are moving stored resources from the roots to the leaves. Giant ragweed and waterhemp will also benefit from a fall herbicide application, providing extra time in the spring to apply the residual product that is so needed for controlling them.

There are several products that can be used for fall burndown. I would consider using residual products such as flumioxazin (Valor® SX), iodosulfuron (Autumn™ Super), chlorimuron-ethyl (Classic®) or a combination of these type of products—along with 2,4-D and dicamba for the burndown. These products should be applied sometime after soil temperatures at the 2-inch depth are at or below 50°F. Check labels for details on fall applications and rates of these products.

Besides being a more consistent weed control program, there are several other advantages to a fall program:

• This is the best time to control winter annuals, biennials and perennials.
• Clean fields are less likely to attract black cutworm moths to lay eggs and they also eliminate host weeds that support nematodes.
• Clean fields (no winter annual henbit population) will prevent an alternative host for soybean cyst nematode.
• Clean fields prevent nutrient tie-up and allow the cash crop more readily available nutrients at the more appropriate time.
• Clean fields provide a warmer and drier soil in the spring. This in turn helps with crop emergence and earlier planting, usually resulting in better yields and less disease issues.

Considering these points and deploying these strategies will lead you to a more profitable and manageable operation for 2018. Have a safe and enjoyable harvest.

Dawn Kielsmeier is an agronomy sales specialist with Pearl City Elevator in Baileyville, Ill. She has a B.S. in dairy science and an M.S. in agronomy, both from the University of Illinois and has been a CCA since 1993. She is a 2017 Illinois Soybean Association CCA Soy Envoy.