Marestail, common to both pastures and row crops, thrives by stealing much needed sunlight, water and nutrients from your crops, leaving you with lower yields or poor pasture health.
Left unchecked, marestail will grow to 6.5’ tall during summer and winter months. If you’re not mindful of resistance, this tricky weed will continue to grow even after herbicide application. Marestail is resistant to five herbicide groups: PSI Electron Diverter (22), EPSP synthase inhibitor (9, glyphosate), ALS inhibitors (2) , photosystem II inhibitors (5) and photosystem II inhibitors (7), which have different bindings.
Thanks to marestail’s robust nature, it can be prolific in fields across the U.S. It’s important to be mindful of this weed in your fields and to scout and track resistance. Your state’s marestail population may not be resistant to all five herbicide groups yet, but it’s just a matter of time.
But there are things you can do. Use multiple, effective modes of action to combat this hardy weed and also attack its weaknesses. Marestail does not recover from deep tillage very well, and it really suffers when the crop reaches canopy. Consider tillage and pre-emergent herbicides with residual to target the weed’s weaknesses.
Continue to scout after tillage and any herbicide application to determine weedkill and where you may have resistance issues.
As you scout, look for these key characteristics to determine if the weeds in your fields are marestail:
- Hair covers the entire plant.
- Cotyledon leaves are oval and tiny.
- Young leaves are egg-shaped, with toothed edges that develop hair as they mature.
- True leaves are alternate, narrow, typically toothed, approximately 4” long, grow along the stem and get small as they near the top.
- Flowers are small, white or yellow and at the top of the stem.
What techniques have you used against marestail? Do you see it more in row crop fields or pastures? Let us know in the comments.