While they're known and planted for their ornamental beauty and fragrant white blooms, magnolia trees are susceptible to some common fungal diseases that can rob them of their splendor. These diseases can affect each part of the tree, from trunk to leaves. The diseases are easily identified by specific symptoms, and if caught in a reasonable time can be treated easily.
Magnolia's Fungal Diseases
The most common fungal diseases that affect magnolia trees are verticillium wilt, leaf blight, nectria cankers and leaf spot.
Verticiullium wilt alters the appearance of the leaves causing them to appear wilted and pale. Leaf blight attacks the undersides of magnolia leaves with threads of matted fungus.
Nectria cankers create pronounced injuries on a magnolia's trunk and branches. Leaf spot, as its name implies, attacks the foliage of magnolia trees.
Leaves infected with verticillium wilt fall prematurely and, in more advanced cases, branches die and the disease may kill the tree. Leaf blight causes leaves to mat together, die and then hang from the tree's twigs. The round lesions produced by nectria cankers cause the branches to dieback--dying from the tip of the branch back--and an advanced case of the disease can lead to death of the tree. Leaves that are infected with leaf spot become discolored, displaying yellow, black or brown blotches, and heavily infected leaves will fall prematurely.
For trees with a light infestation of verticillium wilt, prune the diseased branches. Heavily infected trees should be removed from the landscape. As with verticillium wilt, infected branches should be pruned and destroyed. Proper maintenance is the best defense against nectria cankers and leaf spot. Large areas of a magnolia that are infected with the cankers are incurable. Promptly remove and destroy any infected leaves from the tree.
The best way to prevent magnolia fungal diseases is to exercise diligence with watering and fertilizing regimens. This will help maintain an overall healthy tree.