Field Facts: Woolly Cupgrass

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Wooly cupgrass IandI article

Herbicide-resistant weeds, such as waterhemp, giant ragweed and marestail, are likely already on the radar for most of your customers. But now, a fourth troublesome weed is making a resurgence after causing yield loss challenges many years ago: Woolly cupgrass.

  • Common names: Woolly cupgrass, hairy cupgrass
  • Scientific name: Eriochloa villosa
  • Cotyledons: Short and wide, parallel with the soil surface
  • Leaf shape: Lance-linear
  • Stems: Covered with short hairs
  • Flowers: Clusters (racemes) arranged in panicles. The group of florets (spikelets) are arranged in compressed groups of one or two.
  • Reproduction: Monoecious (male and female flowers on one plant)

Fast Facts

  • The name “woolly cupgrass” comes from the fringe of hairs surrounding the “cup” where seeds are attached. 
  • Woolly cupgrass has been in the Midwest since the 1950s. Due to its large seed size, woolly cupgrass is more tolerant of preemergence and postemergence herbicides. This attribute has allowed the weed to spread rapidly across the region.
  • Woolly cupgrass plants can grow up to 4 feet tall.
  • Leaves are covered in short, dense hairs that may require a magnifying glass to see. Leaves are likely to have one margin with a rippled edge.
  • Woolly cupgrass plants can produce multiple flushes throughout the growing season.
  • A single plant can produce up to 170,000 seeds, and seeds can survive in the soil for up to five years.1 And even when woolly cupgrass plants are extremely stressed, this weed is still able to produce more than 28,000 seeds per plant.1

Control Tips

Woolly cupgrass poses a greater challenge compared with typical grass weeds due to its prolonged emergence patterns, larger seed reserves and the ability to sprout from greater soil depths. This plant has been observed to emerge after herbicide residual activity stops, causing yield loss in some cases.  

  • Work with your customers to plan a program approach to weed control, and time herbicide applications to ensure fields are safe from both broadleaves and grasses.
  • For the most effective woolly cupgrass control, begin each season with a clean, weed-free seedbed to maximize yield. A critical follow-up component is a two-pass herbicide program approach that uses multiple modes of action.
  • In corn, a good preemergence choice is SureStart® II herbicide followed by a timely postemergence application of Resicore® herbicide. Realm® Q herbicide also can be used postemergence to provide an alternative mode of action against grasses.
  • In soybeans, consider adding EverpreX® herbicide to your postemergence pass for control of woolly cupgrass.

1Hartzler, B., and M. Anderson. 2023. Woolly cupgrass. https://crops.extension.iastate.edu/encyclopedia/woolly-cupgrass

EverpreX®, Realm® Q, Resicore® and SureStart® II are not registered for sale or use in all states. Resicore and SureStart II are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Consult the label before purchase or use for full details. Always read and follow label directions.


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