Date: June 13, 2001
Category: Diseases Subject: Anthracnose, Brown Patch, Pythium, Bacterial
Wilt
The extended rain in many areas followed by last week's dry days triggered
ANTHRACNOSE outbreaks in many areas. This disease is favored by wet conditions
and various stress factors such as compaction, low mowing heights, low
N, poor drainage. The disease may begin in stress areas and then spread
to other areas when mowers carry the abundant sticky spores. Wash mowers
before leaving diseased areas. The foliar stage is relatively easy to
control with fungicides. If the fungus has moved into the crown (look
for the charcoal black fungal structures at the base of the plant), recovery
will be slow if at all.
We are now moving into hot, humid weather with warmer nights. Expect
BROWN PATCH, especially where soil remains moist or in shade and where
nitrogen fertility is high. If night temperatures are going to drop below
59F, save your fungicide spray and let Mother Nature stop brown patch
for free. It probably is not hot enough for PYTHIUM BLIGHT, but Pythium
may be active on seedlings.
BACTERIAL WILT remains a confusing problem. It seems to appear in only
one or a few particularly poor greens. It seems to be restricted to the
annual-type Poas, which are probably going to die anyway at this
time of year. To be safe, try to wait until the green is dry before mowing
and wash the mower off before moving to other areas. Copper-containing
fungicides may reduce bacterial populations, but will have no effect on
infected plants and may cause phytotoxicity. There are no other legal
or ethical chemical controls for this disease. Long term solutions lie
in improving the growing conditions to support bentgrass or nonsuceptible
Poa types.
