• Grass can be affected by several types of fungus.Green lawn image by Peter Kirillov from Fotolia.com
  
  From fairy rings to necrotic ring spot, there are many types of fungi that can attack a yard. Some don't cause much trouble, and some do. Fungi are the most common causes of lawn diseases. These microscopic organisms are spread by air or water, and produce infections when conditions are right. Getting rid of a yard fungus can be a big job.
  
  

Fairy Rings

• The University of California Integrated Pest Management Program notes that fairy rings get their names from the old-time belief that mushrooms grow where fairies dance. These semi-circular or circular bands can be up to 12 feet in diameter and may or may not have mushrooms present. Sometimes a fairy ring is just a circle of very lush grass growth, or a circle of unhealthy or dead grass. Regardless, several different forms of mushroom-producing fungi cause fairy rings to develop.
  
  The treatment for removing fairy rings from your yard will depend on what the fungus is causing. If the problem is a ring of tall, lush grass, you will simply irrigate and fertilize the surrounding area to mask the ring. If the ring is unhealthy grass, thoroughly aerating the area will help get water and oxygen to the grass roots, helping grass to recover. In the case of dead grass or a ring that is heavily infested with mushrooms, removal of the soil and underlying soil may be necessary, with a replacement of sterile soil and new sod or seed.
  
  

Necrotic Ring Spot

• Necrotic ring spot is a serious fungal disease that attacks Kentucky bluegrass. Occurring most commonly in spring and fall when the weather is cooler, necrotic ring spot begins as patches that are between six and 24 inches in diameter that include normal looking blades of grass along with straw and red colored blades that tend lie toward the outer portion of the ring, according to the North Dakota State University Agriculture and University Extension. The ringed areas may form slight depressions in the lawn.
  
  Necrotic ring spot is difficult to control once established and may reappear every year for up to four years. Controlling this lawn fungus requires the use of fungicides, changes in watering and fertilizing habits, soil aeration and thatch control.
  
  

Rust

• Rust is a fungal disease of grass that produces a reddish-orange cast in your lawn. You may notice an orange dust in the air when you mow your lawn, or that your shoes are covered with this orange-colored dust. These are the spores of the rust fungus. In severe cases of rust, the grass will yellow, wither and die. If the grass does not die, it may still be severely weakened.
  
  According to North Dakota State University, humid, warm weather favors the development of rust, but the disease can be controlled easily by keeping your lawn healthy with adequate fertilization and watering. Do not leave lawn clippings on your grass after you have mowed, as this encourages the rust fungus. Fungicides are usually not necessary.