• Rye grass is susceptible to a few serious diseases.The rye image by DayDreamer from Fotolia.com
  
  Rye grass makes a popular grass turf, and rye grass seeds are present in many grass seed mixtures for lawns in a variety of climates. Rye grass also produces an edible grain when allowed to grow tall. Unfortunately, rye grass sometimes gets a variety of diseases that cause discoloration and even grass death.
  
  

Pythium Foliar Blight

• Pythium foliar blight shows up in rye grass as discolored pinkish or reddish patches, according to the University of Missouri Extension. It spreads through water movement, so the patches can spread out in streaking patterns. The disease grows fastest in hot temperatures and high humidities, so it occurs more commonly during summer than cool seasons. According to the University of Missouri Extension, pythium foliar blight can kill large sections of grass without treatment. To prevent this rye grass disease, gardeners should provide good soil drainage. To treat an existing case of the disease, gardeners may have to use a fungicide during the summer.
  
  

Crown Rust

• Crown rust is one of the most common rye grass diseases, according to the University of Florida IFAS Extension. The disease causes orange or reddish (rust-colored) pustules on grass leaf blades. The pustules spread out in stripes on the grass blades. Crown rust can reduce grass growth and stays alive throughout the winter. Oregon State University Extension suggests applying a fungicide at the first sign of the disease.
  
  

Pink Snow Mold

• Pink snow mold, also called microdochium patch, often shows up on grasses that have been covered in snow all winter. However, the University of Missouri Extension explains that it can also show up on grasses that did not have snow covers. The disease appears on rye grass as round pinkish circular patches that usually show up in the spring. It spreads easily through mowing, so gardeners should treat the disease before mowing the lawn. The University of Missouri Extension suggests a fungicide to kill the snow mold. Gardeners that have pink snow mold regularly each year can even apply fungicide during the late fall or early spring.