dogwood trees - Knowledgebase Question

cheltenham, Pe
Question by coachrock462
April 4, 2010
Is there anything you can do about a dogwood tree that is diseased. The trunk is orange from some fluid that is dripping from the brances. What is that?

Answer from NGA
April 4, 2010


Sounds like collar rot (also crown rot). The most outstanding symptom is the slowly developing canker on the lower trunk near the ground line, referred to as the "crown" region of the tree. The pathogen kills the bark just above the ground level. Often at an early stage of canker development, infected areas of bark will ooze dark-colored fluid. At this time, infections can sometimes be found by gently removing thin layers of bark in the affected area. If the disease is present, the inner bark, cambium, and sapwood show discoloration.

Over a period of months to years, this killed area of bark becomes sunken, dries, and falls away leaving the wood exposed. The canker is then visible and its seasonal progress is not hard to see. As the tree becomes weakened, it is more susceptible to attack by the dogwood borer and is more severely affected by short, droughty periods during the summer.

It is too late to control crown canker after the fungus has invaded a large part of the tree base. However, if the infection is confined to a relatively small area, it may be possible to stop the spread of the disease at the root collar or trunk base by excising the canker. This simple surgical operation can be done by removing all the discolored bark and sapwood in the canker area and, in addition, removing an inch or two of healthy bark and sapwood around the canker with a sturdy, sharp knife.

This freshly wounded area may be susceptible to new infections, so to provide a physical layer of protection, paint the excised area with orange shellac. Then paint the area of exposed heartwood with a good asphalt-base wound paint.

If a dogwood tree dies of crown canker, do not plant another dogwood in the same spot. Azaleas and rhododendrons are susceptible to a root and crown rot caused by the same pathogen, and apple, maple, and horse-chestnut trees are known to get collar rot or bleeding canker disease from this pathogen as well. Choose woody species other than these if you desire to plant another tree or shrub where the dogwood was.

I hope you can save your tree.

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