Managing Glyphosate-Resistant Marestail

On the growing list of glyphosate-resistant weeds, marestail (horseweed) lives near the top. With the ability to produce up to 200,000 seeds per plant, which can travel long distances, this weed has concerned soybean farmers for many years. To add to the problem, this weed has developed resistance to not only glyphosate, but other herbicides as well.

According to Purdue weed science professor Bill Johnson, Ph.D., no silver bullet exists for managing marestail. In a recent “Focus on Soybean” webcast, which you can view for free, Johnson instead offered these five tips to gain ground on this persistent weed:

• Rotate crops.
• Use spring, pre-plant tillage since marestail does not easily survive tillage.
• Use multiple burn-down applications – both fall and spring treatments.
• Use full rates of residual herbicides in the spring.
• Do not rely on glyphosate or 2, 4-D alone.

“Farmers need to do as much damage to marestail before soybeans come out of the ground as possible. Once they come out of the ground, there are very few tools to use,” Johnson says.

The soy checkoff sponsors these webcasts through a partnership with the Plant Management Network, and all U.S. soybean farmers have access to this full presentation for free until August 31.