| Dollar spot is caused by fungi in the genera
Moellerodiscus and Lanzia. Formerly, it was
attributed to Sclerotinia homeocarpa. The disease is
a common problem on golf courses, but it may also
be prevalent in bluegrass and fine fescue lawns. It
occurs from late spring to late fall and is most
prominent after cool moist weather.
Symptoms and Diagnosis
The disease is typified by small circular areas of
straw-colored grass, which range from one to six
inches across. These circular areas may grow
together to form large, irregularly shaped areas.
Examination of individual leaves will show strawcolored
lesions with reddish-brown borders. The leaf
tip may remain green while the lesion extends
across the blade. A white, spider web-like growth
covering the infected area may be visible in the
morning, especially if dew is present.
When examining samples for symptoms, don’t just
look at the infected areas. Check the fringe areas
where there is some healthy material and part of the
sample is on the decline, thus inspecting a sample
in all phases of the disease.
Life Cycle
The dollar spot fungus survives unfavorable
temperature and moisture conditions in plant tissue
and thatch as dormant, compact masses of
mycelium called sclerotia. It can grow over a wide
range of temperatures (50 to 90 degrees F), but
disease development is greatest at temperatures
between 70 and 80 degrees. The fungus needs
moisture from dew, light rain, or irrigation to infect
leaves, but once established, it can progress even
during times of low moisture.
Integrated Pest Management Strategies
1. Fertilizer. Low nitrogen and potassium levels in
the soil can increase the severity of dollar spot,
but excessive nitrogen increases the susceptibility
of grass to dollar spot and other diseases. Avoid
applying high levels of fertilizer in the fall. Use a
soil test to establish a balanced fertilizer program.
2. Remove excess thatch. Thatch greater than 1/2
inch thick can lead to moisture stress and
predisposition to dollar spot.
3. Mow. Mow frequently at recommended heights.
4. Watering. Water to a depth of about 6 inches.
Frequent watering provides an ideal environment
for disease development once it is started. Water
early in the day so that foliage dries quickly. Do
not water late in the day when the grass will
remain wet for several hours.
5. Promote drainage, shade reduction, and
increased air movement. Provide good surface
and subsurface water drainage to reduce humidity
in the turf. Reducing shade and increasing air
movement over turf can also help speed drying.
6. Cultivars. Select resistant cultivars. Before
seeding, consider recommended cultivars that are
resistant to dollar spot. Consult with experts to
obtain a list of less susceptible cultivars. Then use
a mixture of at least two or three of these to
diversify the lawn and reduce disease spread.
7. Fungicide. Once the disease has been identified,
use a preventive fungicide program with
recommended fungicides. Read labels for proper
fungicides and their use. Pesticides registered for
use include: chlorothalonil (Daconil),
cinnamaldehyde (Cinnamite), iprodione (Chipco),
mancozeb, maneb, thiophanate methyl (Cleary
3336), thiram, triadimefon, and vinclozolin. | 
