Diseased Trees


Two well-known diseases continue to be a threat in the City. Dutch elm disease and Oak wilt are still infecting trees throughout the city.

Dutch Elm Disease

Dutch elm disease is a very common problem throughout the city each year. Tell-tale signs of the disease include “flagging,” where an entire branch of leaves will turn yellow and then brown creating a sort of “warning flag” in the tree canopy.
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According to city ordinance, the property owner must remove infected trees within 20 days of notification by the city. The disease can be controlled through proper sanitation measures.

Elms are great shade trees. There are now disease-resistant varieties available at local garden centers.

Oak Wilt

While not overly prevalent in Chanhassen, oak wilt has been diagnosed on several trees in throughout the city. Watch your oaks, particularly red and pin oaks, each summer for branches full of dead, brown leaves and/or a rapid decline in health.
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Bur Oak Blight

Bur oak blight is often mistaken for oak wilt. This fungal disease only affects bur oaks, causing their leaves to form wedge-shaped dead areas, brown leaf veins, and dead leaves that persist through the winter.
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Bur oak blight is not fatal to bur oaks, but repeated infections over several years can weaken the tree leaving it vulnerable to fatal attacks by two-lined chestnut borer or armillaria root rot.


The city provides free diagnosis of tree diseases. If you suspect your elm or oak may be infected or have other trees in your yard that are unhealthy, contact the Environmental Resource Specialist.