Difficult to rid yard of fungus
They’re back. Fairy rings are making a mess out of attractive lawns. Our recent rains have revitalized those funny dark green rings in lawns around the region, That seem to defy treatment and end up frustrating the lawn owner.
Fairy rings can be created by several dozen different fungi that live on hosts in the soil. The host is usually an old stump, tree branches or construction lumber buried in the soil. The name “fairy ring” comes from folklore that says that wherever fairies danced at night, a ring of mushrooms would appear.
Poorly maintained, drought-stressed lawns on light sandy soils are often the most affected. Lawns with a heavy thatch build-up are particularly susceptible to the fungus.
The main body of the ring is underground where we can’t see it. The only evidence we usually see are white mushrooms in the ring of dark green grass. The mushrooms are actually the fruiting body of the fungus and shed spores rather than seeds. The spores drift on the wind until they come in contact with a host.
The spores can lie dormant on the host for a number of years waiting for the right conditions. Once the spores find themselves in the right conditions, they begin building a mass of fine white filaments called mycelia. These filaments grow and spread out from a source point, forming a dense mat as much as a foot thick below ground. There can be more than one ring in a yard.
As the mycelia spread, they break down organic material and release nitrogen into the surrounding soil. This nitrogen is picked up by the grass at the leading edge of the spreading fungus, turning it a nice dark shade of green as if it had been fertilized.
As the fungus advances, the green zone moves out and leaves behind an ever enlarging patch of weakened or dead grass. The fungal layer inside the ring becomes so dense that it severely restricts or stops the movement of air and water through the soil to the grass roots. This lack of water and air causes the grass to weaken and die inside the ring.
There is no quick or easy cure for fairy rings. Don’t be tempted to try lime, salt, fungicides or other supposed quick-cure remedies. Using them can actually cause more damage than the rings ever will.
This leaves two courses of action. You can simply leave it alone and let it grow out of the lawn after a few years. The fungus may even disappear on its own permanently or for a few years. You can apply fertilizer on a regular basis to the entire lawn to mask some of the symptoms.
If you are not willing to leave it alone, there is only one way to eliminate it. You have to get water through the filament mat. This method is based on research done by scientists at Washington State University and will take about a month of time and close attention to procedures. No shortcuts or quick fixes.
• Rake the mushrooms up or mow them off with the lawn mower. They will not hurt the lawn.
• Aerate the soil with a spade fork or crowbar to open passages to the roots. Go down at least 3 inches. Punch as many holes as you can, moving the fork or bar back and forth as you go to break up the soil profile even more. You can core aerate but the coring tubes may not be long enough to give complete penetration.
• Apply a wetting agent such as liquid dish soap or a commercial product to help the water penetrate the soil. Use 1 teaspoon of soap per gallon of water and pour several gallons on the ring. The soap will not hurt the grass or kill the fungus; the soap breaks down the surface tension of the water, allowing it to flow more easily.
• Drench the area thoroughly to the point of having standing water. Do not use a sprinkler — it will not get enough water on the lawn. Use a hose for large areas and buckets for small ones.
Now the hard part: Repeat the second, third and fourth steps every three days for four weeks. The fairy rings will begin to disappear after about two weeks but do not give up. This process, though tedious, DOES WORK.