• Commonly used on golf courses and athletic fields due to their resistance against wear and tear, rye grasses (Lolium spp.) also form a lush green carpet on homeowners' lawns. Native to Asia and Europe, the two major types of rye grasses--annual and perennial--are planted in isolation or mixed with other grass seeds to get the desired pasture, turf or lawn grass. However, brown patches in the grass make it less attractive and susceptible to damage.
  
  

What Causes Brown Patches?

• Brown rye grass can indicate the presence of a fungal disease. Rhizoctonia blight or brown patch is attacks cool-season turf grasses, such as rye grass, when humidity is high or nighttime temperature is warmer than 68 degrees Fahrenheit. The damage will not be permanent unless it occurs in plantings less than a year old, a University of Kentucky College of Agriculture report, Brown Patch Disease in Kentucky Lawns, explains. Perennial rye grass is more susceptible to the pathogen that causes the disease.
  
  

What are Ideal Conditions for Fungi Growth?

• The fungi--rhizoctonia zeae or rhizoctonia solani--cause brown patches in otherwise green rye grass. A consistent daytime temperature of 63 degrees Fahrenheit, along with 90 percent humidity or rain, is required for the fungi to survive, according to the University of Kentucky College of Agriculture website. Temperatures higher than 80 degrees F. accompanied by high humidity create ideal or ripe conditions for these fungi to activate; if the conditions remain consistent for at least eight hours, chances of R. solani fungus activating are higher.
  
  

Are There Other Causes of Brown Rye Grass?

• Feeding rye grass excessive fertilizer during spring and summer increases the likelihood of brown rye grass occurring. Over watering, irrigating the grass late in the evening or at night, poor air circulation and poor drainage also make the grass susceptible to turning brown. Allowing excessive thatch to accumulate, mowing the grass when it is wet or using dull blades when mowing increases the severity of brown rye grass.
  
  

What Are the Indications of Disease?

• Circular brown patches that range from 1 to 5 feet wide indicate the presence of the disease. Sometimes the intricate gray cobwebs that indicate the fungus also are visible in the early morning. The disease usually occurs during July and August. The University of Maryland website suggests carefully observing perennial rye grass planted less than a year ago for symptoms.
  
  

How Do I Treat Brown Rye Grass?

• Brown patch affects grass sheaths and leaves but avoids crown and roots, which is why it is possible to restore infected areas to health in the fall. Follow the fall fertilizing schedule between September and October, irrigate in the morning so the turf grass dries up by evening and mow the grass down to 2 ½ to 3 inches. Dethatch frequently to promote good air circulation. Apply fungicide over infected areas when signs first appear, no matter what the determined cause.
  
  

How Do I Prevent Brown Rye Grass?

• The University of Maryland's website suggests using a slow-release nitrogen fertilizer in fall. Collect clippings from infected grass and discard instead of leaving them as you normally would.