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Anthracnose: a plant disease
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[APRIL
1, 2005]
URBANA -- Anthracnose is an
airborne disease that can affect lawns, flowers and vegetables, and
trees, said James Schuster, a University of Illinois Extension
horticulture educator based in Cook County. |
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"It is caused by
several different fungi, and there are separate varieties for lawns,
flowers and vegetables, and trees," he said. "Wet weather is what
the anthracnose fungi need to infect and spread."
Ash trees seem to
be one of the first to show infection due to anthracnose. Symptoms
include small to medium-size brown spots on the edges of the
leaflets. These spots may cause the leaflets to become distorted.
"On large trees,
anthracnose is usually worse on the lower leaves/branches where
there is less sun and wind," said Schuster. "The severity of the
infection is dependent mainly on how long the leaves and their
leaflets stay wet."
Schuster said that
a fungicide treatment is usually not recommended, because by the
time the disease is evident, it is too late for fungicides to be
effective. Preventive sprays are not often suggested, since the
rainy weather that favors the disease is the same weather than helps
to wash the fungicide off the tree.
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"The disease is
not fatal to the tree," said Schuster. "The tree would need to
suffer severe defoliation and have another problem that would
combine to weaken it enough so that another disease or insect
problem could kill the tree. Very seldom does anthracnose get bad
enough on an ash to cause any major problem.
"However, if it
does, feed your tree in the fall as it goes dormant. This helps the
tree build up its food reserve and be better able to withstand more
serious diseases.
"Infected leaves
can also be removed and destroyed. Because the disease is airborne,
however, the removal of infected leaves will not stop the disease
from blowing in from some other ash tree that is infected."
Schuster said the anthracnose that affects flowers and vegetables
often occurs later in the growing season. Wet growing conditions are
required to host the disease.
[University
of Illinois College of Agricultural, Consumer and Environmental
Sciences news release]
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