This time of year I get phone calls, txt messages and office visits from concerned people about stinging nettle or fireweed (Urtica chamaedryoides) and how to control it in area hayfields and pastures. Fireweed leaves look similar to strawberry leaves. This pest has square stems and small pale green flower clusters. Small stinging hairs are found on the stems, petioles and leaves and they contain a toxin. This toxin can cause a burning and stinging sensation wherever it comes in contact with your skin and can last for hours. Cattle tend to avoid this pest but could possibly cause some issues for horses. Below is an example of fireweed from an area pasture.
How do we control it? According to information from University of Florida, GrazonNext HL (24 oz/A), Remedy Ultra (1 qt/A), or Pasturegard HL (24 oz/A) is very effective on this weed. These products achieved 90%+ control of this weed 2 weeks after application. 2,4-D and Weedmaster had poor control of fireweed. Please read label before using these products.
More information on the pesticides mentioned above is included in the PERENNIAL GRASS section of the UGA PEST CONTROL HANDBOOK.
How effective is mowing? Mowing provides no control of fireweed. The seed of this pest is surrounded by a sticky substance which can allow to be transported by equipment.
If you would like more information please look at the resources below or contact your county Extension agent.