LSU AgCenter Horticulturist Examines Mushrooms Rings in Lawns

Thomas J. Koske  |  10/26/2006 1:56:56 AM

Mushroom rings often appear in your lawn during the cool, moist days of fall. Though they may be attractive, the mushrooms are poisonous. See mushroom ring story at left for more information.

News You Can Use For November 2003

On cool, moist days, we may see mushrooms sprouting up or doughnut-like rings of dying or dark green grass developing on the lawn. These doughnuts are referred to as fairy rings, according to LSU AgCenter horticulturist Dr. Tom Koske.

Whether a ring or part of a ring, the patterns are brought about by any of many genera in the Basidiamycetes class of true fungi, the LSU AgCenter horticulturist explains. This fungi class includes at least 50 poisonous, edible and questionable mushrooms. Thus, he recommends NOT eating fairy ring mushrooms.

Rings form as the fungus advances outward in search of organic food sources at the inner and especially outer edges of the rings. As the fungus advances it converts proteins of the thatch and soil organic matter into nitrogen. This nitrogen makes grass become greener and more vigorous in a doughnut-like pattern. These rings are classified into types I, II and III.

Types I and II fairy rings have no toadstool fruiting structures readily visible, Koske says. Type I forms rings or arcs with dying bands. Type II forms rings of dark green bands.

"Type III fairy rings have the mushroom structures we see in our lawns," the LSU AgCenter horticulturist says. As environmental conditions get right for Type III fruiting (as they would with good moisture and temperate days), the nutrient-packed fungi quickly change from vegetative growth to reproductive growth and develop the toadstool over several days. These toadstools then develop seed-like spores, which are their means of sexual reproduction.

"Although fairy ring damage is rarely serious, the disease is often unsightly, especially on a well-managed lawn, green or fairway," Koske points out.

Typical ring patterns develop over a wide range of soil types, fertility levels and climatic conditions. Poorly maintained, drought-stressed turf on light, sandy soils often suffers the most. Heavily thatched lawns are particularly susceptible to injury by fairy rings.

Koske says control of Type III fairy ring is not usually necessary except on a golf green, where it turns golf into a game of bumper pool. The horticulturist says to pick off and discard toadstools before they fully open. You also may mow off the mushrooms or just leave them alone.

The horticulturist also recommends contacting an extension agent in your parish LSU AgCenter office to learn more about mushrooms and fairy rings. In addition, look for publication #2887, "Fairy Rings and Mushrooms in Lawns." It can be seen at the louisianalawnandgarden.org or lsuagcenter.com Web sites.

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On the Internet: LSU AgCenter: http://www.lsuagcenter.com/

Source: Tom Koske (225) 578-2222, or tkoske@agcenter.lsu.edu

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