The native American river birch tree (Betula nigra) offers higher resistance to disease and insects than other birch tree varieties. It grows widely across the eastern United States where it dominates other plant and tree species. It offers ideal habitat cover to wildlife, and the seeds of the tree provide a valuable food source for many animals. The tree can grow 80 feet tall with reddish bark that peels in papery strips, giving the tree a scaly appearance.
The reddish bark of the river birch tree appeals to a wide variety of tree enthusiasts with its unique scaly appearance. The bark peels in papery thin strips that help add wintertime interest. A fully mature river birch tree has bark that displays deep ridges, interspersed by scales. The bark turns a dark reddish brown with reddish-green scales. The red bark of the river birch tree varies by cultivar.
The river birch and other birch varieties often suffer from birch tree canker. Nectria galligena, Melanconium betulinum, Botryosphaeria dothidia and B. obtusa fungal infections can cause unsightly cankers to form on the bark of the river birch. The wood fungi Piptoporus betulinus, Fomes fomentarius,Ganoderma applanatum, Inonotus obliquus and Phellinus laevigatus can attack the wood and bark of the river birch if the tree is stressed.
Cankers cause circular, sunken spots to form on the bark. Over time, the cankers enlarge, killing the outer layers of bark and affecting the inner wood. If the canker gets large enough to completely girdle the tree's trunk or branches, the portion of the tree above the canker will die. The wood fungal infections cause entire branches to die. On the tree's trunk large tumor-type growths will appear to expand out of the tree's bark.
Cankers occur on a tree that has not received adequate water or nutrients which can weaken the tree over time. A river birch tree that receives abundant water during times of drought has a better chance of preventing fungal cankers from forming. Wood decay fungi infections often occur on weak trees that have sustained injury from improper pruning practices or over-cultivation that caused an injury to the tree's bark. Once inside, the wood the fungi quickly begins to invade a large area.
No cure exists for fungal canker and fungi wood diseases. If the infections occur on the tree's branches, prune away the branches and promptly discard. Avoid wounding the tree through over-cultivation. Prune only the tree in the late spring when the tree's foliage has emerged. Trees that are pruned in early spring before the leaves can develop large, sap-bleeding wounds that can weaken the tree. The wound causes the tree to lose both valuable water and nutrients.