| Take-all patch of bentgrass is caused by
the root rotting fungus Gaeumannomyces graminis (formerly
called Ophiobolus graminis), and is one of the "patch
diseases" that include bentgrass dead spot, summer
patch and necrotic ring spot on bluegrasses, and spring
dead spot of bermudagrass. These patch diseases are often
grouped together because the fungi that cause them are closely
related and share a number of similar traits, and symptom
patterns are very similar. Take-all patch can be a severe
disease on new construction or renovated bentgrass turfs;
it occurs much less frequently on older, existing stands
of creeping and colonial bentgrasses.
Disease symptoms first appear in early summer following
cool, wet springs such as we have experienced in '02.
Symptoms include yellowing and stunting of infected plants
in a distinctive circular patch, and plants may wilt rapidly
and turn reddish brown to dark brown in color on sunny,
dry days (see Photo 1 & 2). Infected plants
often have roots with brown vascular discoloration, and
stolons and crowns may be rotted if infections are more
extensive (see Photo 3&4). Diseased patches
gradually thin-out, and unaffected grasses (Poa annua)
or weeds (clover, dandelions) often invade the center
of the patch. On some perennially occurring diseased patches,
bentgrasses may recolonize the center of the patch, giving
the distinctive "frog-eye" symptom pattern.
Root infection is favored by soil temperatures in the
50-55 F range, by wet soils (or wet weather in general),
and by high soil pH. Although we usually see this disease
on new bent fairways on native soil, symptoms can be much
more severe on sand based rootzones of greens and tees.
This is primarily due to the increased moisture and nutrient
stress that plants growing in sand rootzones face, and
may also be due to the lack of antagonistic micro-organisms
in sand construction rootzones. Symptoms can often be
suppressed or masked by hand watering and light fertilization
to relieve stress on surviving plants, and by the use
of acidifying fertilizers to change the rootzone pH. Sites
that have perennial occurrence of take-all patch may see
a gradual reduction in disease, presumably because of
the increase in antagonistic micro-organisms over time.
This phenomenon is called "take-all decline."
As with most patch diseases, control of take-all patch
with fungicides can be difficult and costly. Our research
and field- testing experience in Illinois has found that
mid to late autumn and early to mid spring preventive
fungicide applications can reduce the severity of take-all
patch later on. Applying fungicides on a curative basis
once symptoms have developed is too late! Systemic fungicides
in the benzimidazole, demethylase inhibitor (DMI), and
strobilurin (QoI) classes have fairly good activity when
they are applied at high label rates and are lightly watered
into the rootzone. This approach is generally only recommended
for sites that have a history of developing take-all,
or are high value new installations where prevention of
an initial take-all outbreak is important (eg methyl bromide
renovated greens).
See Fungicide Recommendation
Table for more information.
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Photo 1
Photo 2
Photo 3
Photo 4
(click on an image to enlarge
it.)
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