Field Facts: Woolly Cupgrass | Inputs & Insights | Corteva Agriscience

Field Facts: Woolly Cupgrass

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Woolly cupgrass

There are a few natural attributes that make grasses easier to control than broadleaves. However, this is not the case with woolly cupgrass. This weed is a bit more problematic than your typical grass weeds, as it will emerge over a long period of time, has larger seed reserves and will emerge from greater soil depths.  

  • 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 to 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. This weed spreads rapidly across the region because its large seed size is more tolerant of preemergence and postemergence herbicides than other grass species.   
  • 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.  

Control Tips: 

Herbicide-resistant weeds like giant ragweed and waterhemp often take priority in customers’ weed control programs. However, woolly cupgrass caught a lot of Iowa farmers by surprise during the 2020 and 2021 growing seasons. The weed emerged after herbicide residual activity stopped, causing yield loss in some cases.  

  • Work with your customers to plan solutions and timing 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, customers can use a Group 15-containing residual solution, such as Resicore® herbicide, preemergence in combination with a product such as  Realm® Q herbicide in their postemergence pass to give those grasses different modes of action.  
  • Kyber® herbicide is the recommended preemergence solution for soybeans, followed by a postemergence residual herbicide such as EverpreX® herbicide.  


EverpreX®, Kyber®, Realm® Q, and Resicore® are not registered for sale or use in all states. Resicore is 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. Always read and follow label directions. 


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