Canker and Dieback of Lombardy Poplars

By The Old House Web

Canker and Dieback of Lombardy Poplars

The dieback of Lombardy poplar, so noticeable along roadways and windbreaks, is caused by the canker fungi Dothichiza populea and Cytospora chrysosperma.

Symptoms: Symptoms are typical for a severe dieback. Dead branches are scattered through the canopy, particularly in the upper branches. Closely examining a dead branch reveals that cankers have girdled the branches. The cankers are oval, sunken areas surrounded by callus. Dead bark may cover the canker, or it may peel back to reveal deadwood. As the tree continues to decline, it may produce sprouts from the trunk. Eventually the entire tree dies.

Cause: Each spring during wet weather, spores are formed in ooze from fruiting bodies that cover the margins of old stem cankers. The spores are rain splashed onto leaves or bark wounds. Infection generally occurs through the leaves, then progresses down the twig and into large branches, where a canker forms. The canker increases in size yearly until it girdles the branch and kills the branches above it.

The Lombardy poplar is very susceptible to the canker- forming fungi. Many other species are susceptible, but the disease is seldom as serious a problem on black and balsam poplars, Norway maples, and black and eastern cottonwoods.

Control: Examine Lombardy poplars in your county if dieback is evident. No controls are available, so avoid planting Lombardy poplars. Pruning infected branches and fungicidal sprays on foliage are not effective.

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