Reigning Over Horseweed
The Glyphosate, Weeds and Crop Group put together a bulletin on
glyphosate-resistant horseweed, marestail, suggesting it is a significant challenge for no-till farmers, in particular. To deal with the problem, growers have tried tank mixing additional herbicides with glyphosate, but a significant number of glyphosate-resistant horseweed populations are also resistant to ALS inhibitors or other herbicide modes of action.
Some no-till growers have even returned to spring tillage in an attempt to control glyphosate-resistant or multi-resistant horseweed. Because horseweed seeds are easily spread by wind, no-till growers who have implemented management strategies may still be impacted by this weed, if it is nearby or on a neighbor's field. This underscores the importance of using proactive, rather than reactive strategies for weed management.
According to the Glyphosate, Weeds and Crops Group, the primary goal of a horseweed management program in no-till soybeans should be effective control of emerged horseweed plants prior to planting. Consider these points for your horseweed control recommendations:
- 2, 4-D ester should be included in preplant herbicide treatments when possible
- Herbicides should be applied before horseweed plants are 4 to 6 inches tall
- Herbicides applied in the fall will control emerged horseweed, but may not adequately control spring-emerging plants
- Spring applications prior to early May should include a residual herbicide to control later-emerging plants
For more specific information, check out the recommendations section in the horseweed management bulletin.
To deal with horseweed and other troublesome weeds Syngenta recommends:
- Scout fields
- Use effective herbicides with different modes of action
- Use full rates
- Apply when weeds are small (less than 6 inches)
- Control weed escapes
- Avoid spreading seed on your person by cleaning your clothing between fields
- Control weeds in fence rows and ditches
Check out more Syngenta recommended management options and product that can be used to help control horseweed. Also, this bulletin from The Glyphosate, Weeds and Crop Group provides some interesting information about resistant weeds.