With all the rainy weather in Oklahoma this May, we are seeing more turf disease, more weeds, and even mushrooms sprout up in lawns. These mushrooms are interesting, but don’t usually harm turf or plants. Most mushrooms are mycorrhizal (symbiotic association with tree roots) or saprophytic (live on dead organic matter such as wood, etc.) in the soil. When it is warm and very moist as the soil is now, mushrooms are simply the fruiting structure of fungi that is usually just decomposing dead organic material in the soil, such as old wood or tree roots. Don’t worry about spraying with a fungicide, as it’s not needed nor would it do any good, as the fungus is below the soil. If mushrooms are a nuisance, pick them and dispose of them as soon as they appear. Remove sources of large organic debris from the soil, such as old tree roots and decomposing wood. Mushrooms tend to go away as soil dries, so they will be gone once this wet weather pattern goes away and it gets hot and dry this summer.
There are some mushrooms associated with arc-like or circular patterns in turfgrass called fairy
rings. The ring pattern is caused by the outward growth of fungal mycelium, which forms a dense, mat-like structure in the soil that decomposes organic matter. This decomposition releases nitrate into the soil, which in turn stimulates the growth of dark green grass at the outer
portion of the ring. The fungus also may release certain byproducts that are toxic to the turf, leading to brown or dead turf next to the ring.
Fairy rings are difficult to control, other than digging out the areas affected and replacing with new soil and sod. A turf fungicide may be applied, but we recommend to just wait for hotter and drier weather, and the problem seems to go away. If the problem is severe, we can apply a fungicide labelled for fairy ring disease, but remember that this is only when the mushrooms are found in an arc pattern, associated with the turf disease.