Dead Bark on Magnolia Trees

Canker Disease

• Canker disease, which is caused by several species of fungi, can result in dead bark on a magnolia tree. A canker displays as a depressed area on the trunk, stem or branches of the tree that contains a collection of dead tissue surrounded by a circle of callused tissue. The dead bark discolors and oozes a fungal resin, while fruiting bodies of the fungus appear on the branches or leaves of the magnolia tree.

Canker Management

• The canker may girdle --- strangle --- limbs of the specimen, depriving it of water and nutrition. This may lead to stunted growth or even death of the magnolia. Canker management involves pruning away dead leaves and branches and removing all such litter that has fallen to the ground and destroying it. Cutting away the dead bark and canker spots can help to minimize the spread of the disease.

Wetwood

• The magnolia tree is also susceptible to a condition caused by bacteria known as wetwood or slime flux. The problem appears as a spot of stained wood on the bark that oozes a fluid. While it may appear that dead bark has developed on the tree, the infected wood is normally as strong as healthy wood. The bacteria tends to attack only those trees more than 10 years of age and can be managed by drilling small holes in the bark to encourage the bacterial fluid to drain.

Scale Insects

• Scale insects often make their presence known on a magnolia tree by exuding a sticky waste product called honeydew onto the bark of the tree. This honeydew contributes to the development of a condition called black sooty mold, a fungus that is drawn to the honeydew. Dead bark may develop on the tree, branches that are heavily infested by the scale may die and drop, and the vigor and growth of the entire specimen can be stunted.