Are you noticing branch dieback on your poplars or willows? A fungal disease Cytospora canker is showing up again this year. It is especially severe on Lombardy and Bolleana poplars. Branch dieback is usually the first clue you'll have that there is something wrong with your trees. Oval, sunken cankers may be observed on the dead branches or main trunk Cytospora canker disease will cause the bark to turn brown. Black fungus fruiting bodies will develop in the bark. At the present time, you may see orange spore masses exuding from these black fruiting bodies. Infection is through wounds in the tree. Usually infection occurs in early spring when the trees are dormant, but occurred later this year due to our dry hot conditions.

Your best defense against the disease is to keep your trees healthy. Fertilize and water your trees to maintain tree vigor, reduce the chance of infection and increase the chances of your trees overcoming the infection. Avoid unnecessary wounding of your trees. Good sanitation is also important. Remove dead branches as soon as possible. They are frequently attacked by the disease.

During dry weather, prune out the cankers; cutting several inches below the canker. Sterilize your pruning equipment after each cut with rubbing alcohol or a water-bleach mixture. Use a wound dressing to cover all cut surfaces. The value of pruning out diseased wood is not fully proved, but may be helpful where feasible and not an impossible job.

This page was last updated May 2003

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