Brown patch is a fungal disease caused by
Rhizoctoniaspecies. It commonly occurs in hot,
muggy weather when night temperatures are at least 70°F
and daytime temperatures are in the 80s and 90s. It
is favored by heavy rains or watering and by grass
that is dense and at least adequately fertilized.
The disease appears as patches up to two or
three feet wide. The patches may be dark blue initially,
as though under drought stress. The color quickly changes to
purple-brown and then light brown.
The patches may develop green centers and resemble summer
patch or necrotic ring spot. In light
infections, the turf generally recovers in two or
three weeks. When the attack is severe, the crowns,
rhizomes, stolons, and roots may turn brown and
rot, causing turf to be thinned or killed in large areas.
A few cases of brown patch have been
confirmed at the Plant Clinic. Many similar cases have
been caused by drought, not a pathogen.
Brown patch can be prevented with the
cultural practices listed in Report on Plant
DiseasesNo. 411. Once the disease occurs, chemicals may
keep it
from spreading, but long-term control requires
following cultural recommendations. Chemical options are
listed in the 1997 Illinois Commercial Turf and
Landscape Pest Management Handbook.Be sure to read the
label on the selected product for recommended
formulation, rates, and timing for your particular turf
conditions.
Because such applications usually require sprays
at five- to fourteen-day intervals throughout the
summer, fungicide control of brown patch is usually reserved
for golf courses. Products are not always available
in quantities suitable for homeowner use. The
recommendation for a severe infection in a home lawn is to
rake and remove the dead areas, follow cultural
recommendations, and re-seed with a blend of resistant
turf grasses suitable for the light requirements of the
lawn.
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