By Andi Anderson
Midwest farmers often battle herbicide-resistant weeds like waterhemp and giant ragweed. To help address this challenge, the Midwestern Regional Climate Center (MRCC) has developed an online tool called the Weed Emergence Scouting Tool (W.E.S.T.).
This experimental tool predicts when two major weeds—waterhemp and giant ragweed—are expected to first appear and reach peak growth based on weather patterns. By tracking temperature data and calculating growing degree days (GDD), farmers can get an early warning about weed emergence in their counties.
The tool uses a base temperature of 48°F and adds daily GDDs using temperature data from PRISM and forecasts from NOAA. It focuses on counties in the Midwest and updates daily. This allows users to:
- View GDD totals since January 1 for their county
- Check if waterhemp or ragweed will peak within the next six days
- Review current emergence dates for these weeds
Research shows that giant ragweed begins to grow at around 120 GDD and reaches peak emergence between 200 and 300 GDD. Waterhemp, on the other hand, starts appearing at about 425 GDD and peaks between 500 and 600 GDD. These numbers were supported by field studies in Indiana led by Purdue Extension in 2023.
The tool is designed to help farmers time their weed control efforts more effectively, which is especially important as herbicide resistance grows. By managing weeds at the right time, farmers can reduce crop losses and improve yields.
Farmers are also encouraged to send in their weed observations to help improve the tool. Observations can be emailed to mrcc@purdue.edu. With more data, the MRCC hopes to expand the tool’s reach and cover more weed types in the future.
Photo Credit: gettyimages-fotokostic
Categories: Indiana, Crops, Rural Lifestyle