The rains we’ve received in our area of Kansas recently have resulted in the appearance of mushrooms in many a lawn and landscape. Although mushrooms can be eye-catching in size, shape and color, most of them are relatively harmless to plant life. Case-in-point is the fungus referred to as Fairy Ring. It is characterized by its arc-like or circular pattern of growth. This ring pattern is caused by the outward growth of mycelium from the fungus. The mycelium forms a dense, mat-like structure in the soil that decomposes organic material.
As the mycelium breaks down the organic matter, it releases nitrate into the soil, which in turn stimulates the growth of the grass at the outer portion of the ring. The result is a dark green appearance of the grass around the edge of the ring. Unfortunately, that same thick fungal mat formed by the fungus interferes with water infiltration. The fungus can also release certain byproducts that are toxic, leading to dieback of the grass close to the ring. Ergo, in some cases the ring is exhibited by a darker green color and in others, by a brown ring with the outside edge being darker green than the rest of the turf.
Fairy rings are difficult to control. You can sometimes eliminate the ring by digging to a depth of 6 to 12 inches and 12 inches wide on both sides of the ring, refilling the hole with non-infested soil. Or you can try to mask the symptoms by fertilizing the rest of the lawn so that it is as dark green as the ring. This, however, is not such a good idea because it tends to promote other turf problems. Commercially there are certain fungicides marketed that control fairy rings, but these products are not available to homeowners. See http://www.ksre.ksu.edu/bookstore/pubs/EP155.pdf for more info on these fungicides.
Some mushrooms in lawns are not associated with fairy rings. These could be mycorrhizal (symbiotic association with tree roots) or saprophytic (live on dead organic matter such as wood, etc.) types of fungus in the soil. Because some of these funguses are beneficial, you don’t really want to kill them. Besides, applying fungicide spray to the mushroom structures does very little good. Remember the mushroom is simply the fruiting body of the organism. Most of the actual fungus is below ground and not accessible to the chemical.
If mushrooms become bothersome, pick them and dispose of them as soon as they appear. If there are too many for that to be practical, mow them off. If possible, remove all sources of organic debris (i.e. old, dead roots) from the soil. Keep in mind that mushrooms tend to go away as the soil dries. Applying patience may be the best measure of control. FYI, some of the mushrooms in the lawn are edible, but others are poisonous. Never eat mushrooms unless you are absolutely sure of their identity.
Rip Winkel is the Horticulture agent in the Cottonwood District (Barton and Ellis Counties) for K-State Research and Extension. You can contact him by e-mail at rwinkel@ksu.edu or calling either 785-682-9430, or 620-793-1910.
