Field Facts: Woolly Cupgrass
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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 weed is known to emerge after herbicide residual activity stops, causing yield loss in some cases.
- 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)
Field 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
- 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.
- In addition to a strong herbicide program, cultural tactics, such as fertilization, planting date and row spacing, can help make the crop more competitive with woolly cupgrass and other weeds.2
1 Hartzler, B., and M. Anderson. 2023. Woolly cupgrass. https://crops.extension.iastate.edu/encyclopedia/woolly-cupgrass
2 Jones, E., P. Rozeboom, J. Alms, and D. Vos. 2024. Woolly cupgrass management. https://extension.sdstate.edu/woolly-cupgrass-management