How to Identify and Control Red Thread

When lawn disease strikes, your dreams of a thick, beautiful lawn may seem to slip out of reach. But the solution to your problems can be as simple as disease I.D. and changes in your lawn care routine. Most common lawn diseases start with fungal pathogens that can't flourish unless conditions favor their growth. With proper lawn disease identification and disease-fighting culture, you can control disease and enjoy a healthy lawn.

Red thread disease prospers during moderate temperatures, attacking grass leaves from early to late spring and again from late summer into fall. Perennial ryegrass and fine fescue are particularly susceptible to pathogens behind this disease, but red thread affects bluegrasses and bentgrasses, too.1,2

  • Symptoms and signs: Reddish-pink discoloration on your shoes, mower and lawn tools is a clear signal of red thread disease. Closer inspect reveals reddish-pink threads throughout your lawn. Grass leaves wither from the tip to the ground as red thread progresses, creating red-tinged or bleached-out patches in lawns.
  • Contributing factors: Cool, wet spring temperatures provide ideal conditions for red thread's development. Poor air circulation, too much shade, high humidity, and extended periods of wet grass all support this disease. Underfertilizing, compacted soil and excessive thatch also contribute.
  • Cultural control: Remove lawn clippings to improve air circulation and battle red thread disease. Fertilize regularly with premium high-nitrogen lawn fertilizers, and irrigate early in the day so sun and wind dry grass fast. Aerate compacted lawns and remove excess thatch. For shaded lawns, choose grasses that do well in shade.

When cultural controls fail to manage fungal lawn diseases, a lawn fungicide can help. As with garden fungicides, early treatment is key to preventing fungal pathogens from germinating and spreading. Many effective fungicides are available only to lawn professionals. Your local county extension agent is an excellent source for information on lawn fungicides and their use for lawn diseases.

Red Thread (Laetisaria fuciformis) close up.

For any type of lawn disease, choosing disease-resistant grass varieties plays an important role in disease prevention and control. Superior grass varieties such as purebred Pennington Smart Seed grasses are backed by decades of industry-leading research and breeding to provide you with the finest in sustainability-enhancing lawn grasses with outstanding disease resistance.

By being proactive and providing your lawn with the care it needs, you can restore balance and enjoy a thick, healthy lawn again. Pennington is here to help with timely, expert lawn advice and premium seed and lawn care products, so you can know the satisfaction of a disease-free lawn you're proud to call your own.

Pennington with design and Smart Seed are trademarks of Pennington Seed, Inc.


  1. NextGen Turf Research, "Disease Overview: Turfgrass Disease," April 2016.
  2. Bruneau and Lucas, "Diseases of Warm-Season Grasses," North Carolina State Extension, August 1995.

Photo credit: Mary Ann Hansen, Virginia Polytechnic Institute and State University, (CC BY 3.0 US)