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Dogwood Anthracnose
In the Nashville area Dogwood Anthracnose is a real
threat. It attacks Dogwoods, especially Cornus florida,
in early spring and starts as large, irregular, tan to brown blotches
near the edges of petals then appear on tips of leaves. The spots
on the leaves may have dark brown to purple margins. Infection
will usually cause the leaves to drop before autumn. However,
the infected leaves will hang on to encourage the spread of disease.
Worst of all, Anthracnose will attack twigs and even the trunk
causing a girdling effect and eventually killing the tree!
Pathogen:
Discula destructiva is the fungal pathogen that causes
Dogwood Anthracnose. The fungus overwinters on dead leaves and
twigs and is then spread by rain and other forms of splashing
water, ie. irrigation. To prevent the spread of Dogwood Anthracnose
remove all damaged and diseased limbs from the tree and destroy
them. Also, rake all fallen leaves and destroy them as well. Do
not add them to compost.
Environment:
Dogwood Anthracnose loves cool, moist conditions and spreads rapidly
when trees are planted close together, especially as understory
trees. Specimen lawn trees are less likely to be afflicted. To
prevent the development of Dogwood Anthracnose rake all leaves
in the fall and burn them. Also, avoid overhead watering, ie.
set your water sprinklers to water below the tree canopy.
Hosts:
Dogwood Anthracnose vigorously attacks Cornus florida flowering
dogwoods. However, stellar dogwoods (Cornus rutgersensis) and
kousa dogwoods (Cornus kousa) are more resistant to the disease.
Management:
Spraying a fungicide can help to control Dogwood Anthracnose,
but it will not be successful unless the methods mentioned above
are carried out as well. It is a persistant disease and give the
right conditions will kill a tree in 3 to 5 years. When spraying
use chlorothalonil (Daconil) or mancozeb and follow label directions.
Begin spraying in the spring at first bud break. Continue weekly
applications until the leaves mature.
| List of Diseases | Elimination
of Pathogenic Disease Elements |
| Controlling Existing Pathogenic Diseases
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