Mushrooms are Common in Missouri Lawns and Often Become a Concern to Homeowners

At certain times of the year, especially a few days after heavy rains, mushrooms become quite common in home lawns. While many homeowners feel that the mushrooms that appear in a lawn are unsightly, most of these will not harm nearby plants. In fact, many of these mushrooms are the “fruiting bodies” or spore producing structures of fungi that live in the soil in association with tree roots. Called mycorrhizae, these fungi help the tree obtain moisture and nutrients and their presence indicates a healthy tree. Other mushrooms are the “fruiting bodies” of fungi that feed on decaying organic matter in the soil and also may have little impact on surrounding vegetation. Unfortunately, there are also few that might indicate a disease causing pathogen attacking a nearby tree or shrub. The small, honey colored Armillaria mushrooms are an example of a fungus that can cause a root rot in trees under stress.

Some of the mushrooms that survive on decaying organic matter in the soil are part of what are called fairy rings, mushrooms that spring up in circles. Another characteristic of many fairy rings is the dark green circular band of turf that grows more rapidly than surrounding turf. Some of the fairy rings don’t cause much damage to the turf, while others will include a zone where the grass has been killed.

How does a person figure out what kind of mushroom they have? There are certainly many guides to fungal identification, as well as resources on the web. The Missouri Dept. of Conservation has a site that lists several edible and poisonous Missouri mushrooms.
http://agebb.missouri.edu/mac/links/linkview3asp?catnum=156&linknum=6297". Another resource is the University of Missouri Plant Diagnostic Clinic, which can identify samples submitted to the lab. Please see our Website at http://soilplantlab.missouri.edu/plant/index.htm for more information on sample submission and fees.

What should be done about these mushrooms in the yard? We are frequently asked about possible control measures such as fungicides that might be applied to manage the mushrooms. Unfortunately, fungicides have not proven effective for control of these fungi in home lawn situations. In most cases the mushrooms can be removed by hand or be mown off, although mowing could release large amounts of spores

for some species. It’s a good idea to wash hands after handling mushrooms. The MU plant diagnostic clinic will not recommend consuming mushrooms from the lawn, even with the knowledge of an edible species, since some people may have allergic reactions, some fungi may absorb lawn chemicals and other toxic compounds or be contaminated with insects, bacteria or other fungi. For control of plant pathogenic fungi in the lawn such as Armillaria, there is usually no practical way to eliminate the pathogen. The best strategy is maintain plant vigor through good horticultural practices that reduce tree stress, such as watering during drought, avoiding soil compaction and root injury, and by applying fertilizer based on soil test results. Less susceptible tree species can also be planted.

Control of fairy ring can also be difficult. While there are some fungicides labeled for use in commercial situations, especially for extremely high maintenance areas such as putting greens, they are not always effective and aren’t readily available to the homeowner. Other control methods range from removal and replacement of soil to keeping the soil in the area of the fairy ring saturated with water for as long as 4-6 weeks and/or repeatedly tilling the affected area. This could be quite damaging to other plants in the area and be diffi cult to maintain. Most homeowners may find it easiest to live with the fairy ring. It is important to keep in mind that fairy ring is more damaging in underfertilized, lightly watered lawns or lawns with thick layers of thatch. Proper fertility and moisture levels will help mask the symptoms.

Simeon Wright
University of Missouri
Plant Diagnostic Clinic
573-882-3019 WrightSi@missouri.edu