UC IPM Home > Homes, Gardens, Landscapes, and Turf > Mushrooms and Other Nuisance Fungi in Lawns

How to Manage Pests

Pests in Gardens and Landscapes

Mushrooms and Other Nuisance Fungi in Lawns Published 9/02 In this Guideline:
Life cycle of a fungus Mushrooms in lawns Caution: some mushrooms are poisonous Other fungal reproductive structures in the lawn About Pest Notes Publication Glossary

Mushrooms, sometimes called toadstools, are the reproductive (fruiting) structures of some kinds of fungi. Other reproductive structures sometimes found in lawns include inky caps, puffballs, stinkhorns, and bird's nests. Many fungi do not produce visible fruiting structures, including those that cause many lawn diseases. Most fungi in lawns are beneficial because they decompose organic matter, thereby releasing nutrients that are then available for plant growth.

This publication covers mushroom-producing fungi that are lawn management or nuisance problems but do not necessarily cause lawn diseases. Information on turfgrass diseases can be found in the University of California publications Turfgrass Pests and UC IPM Pest Management Guidelines: Turfgrass, listed in References. For information on properly maintaining a lawn to prevent the development of diseases, see Pest Notes: Lawn Diseases – Prevention and Management, also listed in References.

LIFE CYCLE OF A FUNGUS

Fungal fruiting structures release tiny spores that are easily carried on air currents to new sites. When spores reach a favorable place to grow, they germinate and send out long, thin filaments called hyphae. Hyphae decompose wood, fallen leaves, and other organic matter, absorbing a portion as food. A single hypha is too small to be seen without magnification; however, in soil or beneath bark, groups of hyphae are sometimes visible as a mass of white or dark, threadlike growth known as mycelium.

When mycelium has developed sufficiently, fruiting bodies such as mushrooms can be produced. Fungi generally survive in soil for years and only produce fruiting structures when conditions are favorable, such as after periods of prolonged wet weather.

MUSHROOMS IN LAWNS

Because mushrooms are merely the fruiting bodies of fungi, removing them does not kill the underground mycelia from which they are growing. Picking mushrooms, puffballs, stinkhorns, or other reproductive structures soon after they appear may prevent their spores from spreading to new sites. However, because most spores are wind-blown long distances, they can easily come into a lawn from neighboring areas. The primary reasons for removing mushrooms from lawns are to keep them away from children and pets and to improve the lawn's appearance.

CAUTION: SOME MUSHROOMS ARE POISONOUS

Do not eat wild mushrooms or other fungal fruiting bodies unless you are well acquainted with the different species. Many species are poisonous and ONLY an expert can distinguish between edible and poisonous species. There are no simple tests that can be used to identify poisonous mushrooms.

Small children tend to put anything, including mushrooms, in their mouths, so remove all obvious fungal reproductive structures from the yard before allowing a child to play there. Pets may also be harmed by ingesting poisonous fungi.

Fairy Rings

Circular or semi-circular green bands of grass in a lawn may be caused by fairy ring fungi. Rings may be from 1 to 12 or more feet in diameter and mushrooms may or may not be present. Fairy rings get their name from the ancient belief that mushrooms grew in circles where fairies danced. All grasses are susceptible to fairy rings and several species of mushroom-producing fungi may be involved. In central and northern California Marasmius oreades is a common species, while in southern California Lepiota species are more common.

Sometimes the only effect of the fungus is to stimulate grass growth in arcs or circles; this growth is caused by the release of plant nutrients as the fungal hyphae decompose organic matter in the soil. In other cases the soil just inside the ring may become so permeated by the fungal growth that water penetration is retarded and the grass in that area grows poorly or dies. Fairy rings often continue to enlarge for many years. As the ring expands, the older portions of the fungus die, leaving a larger area in the center where weeds and undesirable grasses may become established.

Management. When the only effect of a fairy ring fungus is a ring of tall, green grass, increasing fertilizer and irrigation will usually mask these symptoms.

If fairy ring has caused significant dying or dead areas of grass, then lawn renovation may be required. If the grass is not dead, it can reestablish itself if water penetration is improved by breaking up the dense fungal mat of mycelia. To improve penetration, remove cores of soil that are at least 1/4 to 1 inch in diameter and slightly deeper than the fungal mat.

Determine the depth of the fungal mat by probing the lawn area with a trowel, shovel, or long screwdriver. If the mat is less than 3 inches thick, the use of a lawn aerator a few times a year may be sufficient to improve water penetration. Begin 2 feet outside the margin of the ring and work inwards. Sweep or rake up the cores and remove them from the turfgrass.

If the fungal mat is more than 3 inches thick, a lawn aerator may not be able to effectively remove cores of sufficient length. Also, lawn aerators may not be powerful enough to penetrate some soils. In these cases, a soil probe, small auger, or shovel may be needed to penetrate through and break up the fungal mat. Remove as much of the infested soil as possible. Refill large holes with fresh soil that is relatively free of organic matter.

Dead areas in tall fescue or other bunch-type lawns may need to be reseeded. Creeping grasses like bermudagrass will eventually fill in. After treatment, water until the soil is thoroughly wet. Be sure to wash the coring implement before using it in healthy lawn areas.

In general it is more effective to manage fairy rings in the home lawn with the cultural practices mentioned above than with a fungicide. Fungicides usually require multiple applications and proper timing over a long period of time.

Where complete eradication is desired, remove the soil and sod to at least a depth of 1 foot and 18 inches beyond the outside edge of the ring. Refill the trench with fresh soil and reseed the area. Be careful not to spill any infested soil on adjacent healthy areas.

Other Mushrooms

Mushrooms found in lawns often develop from buried scraps of construction lumber, dead tree roots, or other organic matter. The fungi that produce these mushrooms are beneficial because they decompose organic matter in the soil, making nutrients available to other plants. These mushrooms usually are harmless to grasses, but some people consider them unsightly or want to get rid of them because young children play in the area. Remove mushrooms growing from buried wood or roots by picking them as they appear or by digging out the wood. Many of these mushrooms are associated with overirrigation or poor drainage. Removing excess thatch and aerating the soil to improve water penetration may help in some cases. You can sometimes eliminate mushrooms growing from organic matter by applying nitrogen fertilizer at a rate of 1 pound of actual nitrogen per 1,000 square feet of lawn. The nitrogen should be readily available and not slow-release or water-insoluble formulations. Examples include 5 pounds of ammonium sulfate (21-0-0) or special lawn fertilizers such as 6 pounds of 16-6-8 or 4 pounds of 27-3-4 per 1,000 square feet of lawn. Fertilization hastens decomposition of organic matter.

Inky Caps. Inky caps (Coprinus sp.) are a common and distinctive group of lawn mushrooms. They are so named because the cap of the mushroom decomposes into dark liquid resembling ink shortly after its appearance in the lawn.

Mycorrhizae. Some beneficial fungi, known as mycorrhizal fungi, connect themselves to tree, shrub, and herbaceous plant roots. These fungi help plants absorb nutrients and water from the soil. Mushrooms produced by these fungi can sometimes appear in lawns. Digging up the source of these mushrooms (plant roots) may be detrimental to the plant or tree. Many trees, particularly pines and other conifers, cannot grow or grow poorly without the help of these fungal partners.

Armillaria. Mushrooms growing from the base of a stump or tree in a lawn may indicate that a fungus is attacking the tree. The most common is the armillaria root rot fungus (Armillaria mellea), which often produces clusters of honey-colored mushrooms at the tree base in fall. Several hundred different trees and shrubs are attacked and killed by it. The mushrooms do not usually appear until the host tree is dead or in advanced stages of decline. (For more information on armillaria, see Pest Notes: Armillaria Root Rot, listed in References.)

Mushrooms in Newly Laid Sod. Mushrooms often appear in a new sod lawn during the period of sod establishment. Common species of mushroom include Panaeolus foenisecii, which are small mushrooms with slender stems and brown gills and spores, and cone heads, Conocybe spp., which are small light-colored mushrooms with slender stems and smooth cone-shaped caps. New sod lawns usually require frequent irrigations to become established, creating an ideal environment for the growth of mushrooms. The mushrooms do not harm the lawn and will disappear when irrigation is reduced.

OTHER FUNGAL REPRODUCTIVE STRUCTURES IN THE LAWN

The following fungi do not cause real damage to a lawn, but may be unpleasant, unsightly, a concern for children and pets, or merely a curiosity. They are not infectious or parasitic on lawns but live on decaying plant material.

Stinkhorns. Stinkhorn fungi produce a fruiting body that sticks up through the lawn when mature, resembling a giant finger. The tip of the stalk is covered by spores in a gooey slime that stinks. The terrible odor attracts flies and other insects, which pick up and spread the spores. Dig out or hand-pick the stinkhorns.

Puffballs. The fruiting body of puffball fungi is an enclosed ball that opens or ruptures to release thousands of spores when mature. In lawns, puffballs are usually an inch or less in size, but may be larger. Most puffballs are creamy white on the inside and outside when young. At maturity the inside of the puffball is filled with dark-colored spores.

Bird's Nests. Bird's nest fungi produce fruiting bodies that resemble tiny nests with eggs. Though not eggs, these small spheres contain spores. Bird's nest fungi usually occur in groups that may be a few inches in diameter.

Slime Molds. Slime molds are not true fungi but primitive organisms that grow in similar environments and aid in decomposition of organic matter. They form a gooey mass (plasmodium) that may look like vomit on the lawn surface. This substance may be white, gray, yellow, brown, or red. The mold eventually dries on the lawn surface. Undisturbed slime molds usually disappear in a week or so, but damage to the lawn underneath may result from shading and suffocation. Slime molds can be removed by raking, mowing, or spraying with a stream of water from a hose.

WARNING ON THE USE OF CHEMICALS

COMPILED FROM

Moore, W. S., C. S. Koehler, and A. H. McCain. 1998. Mushrooms in Lawn and Landscape. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 21050.

REFERENCES

Grebus, M. E., J. Hartin, and A. H. McCain. Mar 2000. Diseases from UC IPM Pest Management Guidelines: Turfgrass. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 3365-T.

Hartin, J. S., P. Geisel, and M. A. Harivandi. Jan 2002. Pest Notes: Lawn Diseases – Prevention and Maintenance. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7497.

McCain, A. H., R. M. Endo, and H. D. Ohr. 1989. Fungal Diseases. In Turfgrass Pests. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 4053.

Raabe, R. D. In press. Pest Notes: Armillaria Root Rot. Oakland: Univ. Calif. Agric. Nat. Res.

PUBLICATION INFORMATION

Pest Notes: Mushrooms and Other Nuisance Fungi in Lawns
UC ANR Publication 74100        

Authors: M. Le Strange, UC Cooperative Extension, Tulare Co.; C. A. Frate, UC Cooperative Extension, Tulare Co.; and R. M. Davis, Plant Pathology, UC Davis
Editor: B. Ohlendorf
Technical Editor: M. L. Flint
Produced by IPM Education and Publications, University of California Statewide IPM Program

PDF: You need a PDF reader, such as Acrobat Reader version 8 or later, to view or print this PDF. If no reader is installed on your computer, you can download a free copy of Adobe Acrobat Reader.

Top of page