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Mushrooms
Mushrooms, also called toadstools or puffballs, are fruiting bodies of soil fungi. They appear in
lawns during wet weather in spring and summer. Mushrooms live on organic matter such as roots, stumps
and boards in the soil. Most don't harm the lawn but are unsightly. Mushrooms that grow in arcs or
circles of dark green grass are called fairy rings. The arcs or rings enlarge from 3 inches to 2
feet each season as the fungi grows outward. The fairy ring fungus may interfere with water flow
through the soil and stress the lawn.
There is no chemical control for mushrooms. Time is the best cure. Once the buried wood has completely
decayed the mushrooms will disappear. Break mushrooms with a garden rake or lawn mower for temporary
control. This helps to dry the mushrooms and reduces the risk of children eating them. Control individual
mushrooms by removing the organic matter. Dig up and remove the wood. Fill and reseed, or sod, as
needed.
Description: Heavy rains can result in
the appearance of numerous slime molds and mushrooms in home lawns. Although these organisms are
often spectacular in color and size, most are relatively harmless to the plant life.
Slime molds are primitive microorganisms that can produce white,
purple, orange or brown blobs or patches of fungus-like material known as sporangia (spores). They
can cover turfgrass, strawberries, ornamentals, and numerous other horticultural plants. Slime
mold spore masses, when mature, are powdery and break apart easily during rain or when knocked
around by your shoes. The spores of the slime mold survive in soil or organic debris and germinate
during wet weather to form motile swarm spores. Some of these spores fuse to become amorphous amoeba-like
structures that engulf other organisms or organic matter. Slime molds can actually move or flow
across soil or plant surfaces. Although unsightly, these organisms are not pathogenic to living
plant material. Frequent mowing, raking, or brushing of the spore masses is usually sufficient
to control the problem.
Many different mushrooms can also appear in lawns. Some of these
mushrooms are associated with arc-like or circular patterns in turfgrass called fairy rings. The
ring pattern is caused by the outward growth of fungal mycelium. The mycelium 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 the grass at the outer portion of the ring. This
results in a dark green appearance of the grass at the margin of the ring. Unfortunately, the thick
fungal mat formed by the fungus does not allow for water penetration. The fungus may also release
certain byproducts that are toxic to the turf. This can lead to dieback of the turf in the
ring. 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. Alternatively, 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 really isn't a good idea because it tends to
promote other turf problems.
Recommendations: A couple of fungicides called
Prostar and Heritage may help alleviate fairy ring symptoms. These products should be drenched
into the affected areas. Repeat applications may be necessary. Unfortunately, these products are
not available in retail stores.
Some mushrooms in lawns are not associated with fairy rings. These may be
mycorrhizal (symbiotic association with tree roots) or live on dead organic matter (wood, etc.)
in the soil. Since some of these mushrooms are beneficial, you don't really want to kill them.
Besides, a fungicide spray to the mushroom itself does little good. Most of the fungus is below
ground and inaccessible to the chemical. If the mushrooms are a nuisance, pick them and dispose
of them as soon as they appear. Also remove any sources of large organic debris from the soil.
Some of the mushrooms in the lawn are edible, but others are poisonous. Never eat any mushrooms
unless you are sure of their identity.
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