SHADE TREE ANTHRACNOSE
What is that?
What causes shade tree anthracnose?
- Anthracnose is a leaf disease caused by fungi that are active in
the early spring.
- It can highly disfigure leaves on susceptible trees, and this very
noticeable damage often concerns homeowners greatly, especially in the spring.
- Shade tree anthracnose is separate from dogwood anthracnose,
which is a different disease caused by a much more virulent fungus that requires
early and aggressive management.
- Fungi of the genus Discula (and related forms) are responsible
for this disease.
- The fungi pass the winter on dead leaves on the ground, or occasionally
in cankers on affected twigs in the trees. In the early spring, their spores
are dispersed for reinfection.
- Anthracnose fungi can only affect leaves under cool and moist conditions
typical of early spring. When the weather warms up and dries out, infection
can not occur.
What does it look like?
What should be done about this disease?
- The symptoms include irregular, brown-black blotches, sometimes
paralleling the leaf veins.
- When the weather is particularly favorable (lengthy cool and moist
period), entire leaves can become blighted and significant tree defoliation
- Some important landscape and street trees are particularly susceptible.
They include maples, ashes, sycamores, beech, birch, elm, walnut, and horsechestnut.
- This is a minor blemish that rarely affects the overall health
of the tree. Since this disease will stop as the weather becomes
warmer and drier, there is no need for control measures in most cases.
- Even if defoliation occurs, the tree will put out its second flush
of growth under warmer and drier conditions that prevent reinfection by the
- To help reduce the infection level the following spring, remove
and discard the leaves from a diseased tree in the fall-- or compost them
- If anthracnose is serious near a new planting site, select trees
that are resistant to it.
- Fungicides are rarely recommended.
- If anthracnose is a recurring problem and/or the tree is on a
prominent site, where the damage is esthetically unacceptable, a fungicide
program may be warranted.
- Initiate any fungicide treatment before budbreak; by the
time symptoms can be seen, it is too late to treat the fungus. Check your
local University Extension office for recommendations on products, dosage,
Where can I get more information?
Frederick Berry. 1986. "Anthracnose
diseases of eastern hardwoods." FIDL-NA-133 (product recommendations
outdated). For other information, advice and help on this topic, call
offices of your State Urban Forestry Coordinator or University Extension
service, or visit urban forestry web sites.