Agronomy •  2021-04-12

Weed Scouting: Protecting Your Crop

Woman and man walking through field

Scouting for weeds can be a time-consuming task, but it is essential to achieving high crop yields and managing weed resistance for the long-term.  From weed identification to scouting after herbicide application, we’ve outlined these best practices to help you grow with confidence this season.

How to scout for weeds

While weeds are present in every field, it’s important to remember that there are variations in species and the density of each population.1

Early in the spring, ideally before planting, walk the field in a zig-zag pattern looking for any weeds.  Then, walk the perimeter of the field to see if any weeds are encroaching from the fence rows.  Scouting ahead of planting allows you the flexibility of choosing a pre-plant herbicide for your field.  The later you scout, the less options you may have. Always remember: scout early and scout often.

As you walk, mark the weedy areas on a map, either a paper copy or in a mapping application on your phone.  This will create a record that can be referred to later in the season or in future years.  If possible, identify the weeds in each area and record the type of weed and size, even if you cannot identify the weed.  Take a photo of it or gather a sample and compare to the resources below or send it to your crop consultant or retailer for identification.

Also, take time to think back to last year’s harvest, were there any patches of weeds in the field that you saw from the combine or buggy?  Was the field burnt off last fall?  If you do not have the time or inclination to scout, there are independent crop consultants and retailers with crop scouting programs that you can hire to take this task off your plate. Contact your local Corteva Territory Manager for more information.

Weed Identification

Weeds are categorized into two main types: broadleaf and grass.

Broadleaf plants have wide leaves and veins that branch out in different directions.  In comparison, grasses have leaves that are narrow, emerge as single leaves, and stems that are rounded or flattened.  Once you have established this, you can move ahead to identify the specific weed species.

There are several excellent resources available for weed ID and growth staging. We recommend the following:

Choosing a herbicide

The next step is choosing a herbicide that’s the right fit for your field. Choosing a herbicide is done based on the spectrum of weeds that have been identified in the field and considering the crop’s herbicide tolerance.  With the diverse portfolio of herbicide tolerance in seed that is offered today, it is critical to know what corn hybrid and soybean varieties are planted in each field in addition to the weeds you need to control.   

Corteva Agriscience is committed to Canadian agriculture and is here to help you select the right approach to control weeds to maximize your profitability.  Learn about our portfolio of Eastern corn and soybean crop protection products, check out our Field guide

Application 

When applying your herbicide, be sure to read and follow label directions.  Use the recommended label rate for each herbicide for maximum weed control and to prevent injury to the crop.  Prevent and eliminate weed escapes in field borders and fence rows. These are breeding grounds for weeds, including herbicide resistant weeds. Use a backpack sprayer, hand weeding, or mowing to remove them.2

Follow up after application 

After the label indicated safe re-entry interval has passed and weeds are starting to wilt and perish, make another pass at scouting the field.  This walk through will confirm that you have successfully managed the weeds in the field.  Any weeds that are still alive should be noted, removed and samples collected for analysis as they may be resistant to the herbicide that was selected. Samples can be submitted to Harvest Genomics Inc, a new agriculture biotech company based out of Guelph3 or to the University of Guelph4

For more information, contact us at solutions@corteva.com or contact your local Territory Manager.

1http://www.omafra.gov.on.ca/IPM/english/weeds-herbicides/scouting-for-weeds.html
2https://manageresistancenow.ca/weeds/wfs-how-to-manage-herbicide-resistance-in-your-fields/ 
3https://ontariograinfarmer.ca/2020/06/01/cropside-resistance-test/ 
4https://www.plant.uoguelph.ca/resistant-weeds