| Anthracnose is usually associated with turf suffering
from heat injury in midsummer, but it can also
develop in spring and fall. Anthracnose may occur
in conjunction with other diseases such as summer
patch and Rhizoctonia brown patch. It is a common
disease of bentgrass and annual bluegrass.
The most severe damage is when the anthracnose
fungus (Colletotrichum) infects and colonizes the
lower crown of the turfgrass plant. This is sometimes
referred to as basal crown rot. Plants with a crown rot
are killed, resulting in a thinning of the turfgrass stand.
Spore-producing acervuli and small, black resting
structures called sclerotia form on the decaying crown.
The scattered structures are visible with a hand lens
and appear as small pepper-like dots.
Symptoms and Diagnosis
From a distance, affected bentgrass and/or annual
bluegrass appear unthrifty and have a yellow or
bronze cast. Affected turf may wilt rapidly during
midday and require frequent watering.
Individual plants affected with anthracnose first turn
yellow and then die. Distinct leaf spots are not
commonly formed by the anthracnose fungus.
Instead, individual leaf blades fade from dark green
to light green and then to yellow. There is no distinct
region between healthy and diseased tissue as
commonly observed with other leaf spotting fungi.
The fungus produces conspicuous black fruiting
structures called acervuli in the leaves. The acervuli
are abundant in dead tissue and may also form in
green, apparently healthy leaves. The black hairy or
spiny fruiting bodies are easily visible with a 10X
hand lens. Spines associated with ascervuli are
diagnostic for Colletotrichum fungi.
Life Cycle
Anthracnose may develop throughout the growing
season, although it is more common in midsummer
when cool-season turf is experiencing heat or
drought stress.
The anthracnose fungus, Colletotrichum
graminicolum, overwinters on living plant material.
Stressed turfgrass is most susceptible to infection.
The fungus penetrates the root, crown and/or leaf
tissue during high humidity and wet weather
conditions.
Integrated Pest Management Strategies
1. Fertilizer. Get a soil test and correct fertilizer
deficiencies, especially phosphorus and
potassium. Very light fertilization with a balanced
fertilizer during the summer may help the turf
withstand stresses and recover quickly.
2. Mowing. Low frequent mowings enhance disease
development. Consider raising mowing height to
three inches during midsummer.
3. Watering. Use proper watering practices. Water
in early morning with approximately 1 inch of
water per week or to a depth of 6 inches. Avoid
dry spots and frequent, light waterings.
4. Fungicides. Fungicides are continually being
developed for use against fungi. Select one for
your disease and read the label before applying
any fungicide or pesticide. Pesticides registered
for use include: azoxystrobin (Heritage),
chlorothalonil (Daconil), Neem extract, copper,
mancozeb, maneb, thiophanate methyl (Cleary 3336),
and triadimefon. | 
