Magnolia trees are popular landscape trees. They can be planted in partial shade to full sun and can withstand most soil types from some dense clay to sandy soil. Hardy through USDA hardiness zones 5 to 9, magnolia trees prefer a dry to moist environment, but be sure there is no standing water. Magnolia trees refer pH levels between 4.5 to8. They provide shade and beauty throughout the year.
Leaf blight, found on the leaves and branches of magnolia trees, is a fungal disease. Leaf spot is also caused by a fungus and affects the magnolia tree in rare cases. Leaf spot is caused by watering magnolia trees from overhead rather than into the soil. Verticulum wilt is the final fungal disease that affects magnolia trees. Verticulum wilt lives in the soil and attacks the plant from the roots.
Leaf blight appears at first as a formation that looks like threads on the backs of leaves. These threads mat over time. As the disease spreads, the leaves will begin to stick together. Leaf spot appears as small black, yellow, brown or purple spots on the leaves. As the leaf spots get larger, they will develop a white centre. Verticulum wilt will cause wilting in magnolia trees. There will be no external symptoms except a wilting, dying tree.
Leaf blight affects primarily young trees, and established magnolia trees are rarely infected. Young trees can be damaged extensively as the fungus proceeds and kills the leaves and branches. Leaf spot will cause the leaves to fall from the magnolia tree, and will spread to the branches and trunk if it is not caught. Magnolia trees die from verticulum wilt. Very rarely does a magnolia tree live after the soil has developed verticulum wilt.
Leaf blight can be removed from trees by pruning. Be sure to use sterile pruning shears and get all infected branches. Sterilise the sheers after pruning and burn the branches immediately. An anti-fungal spray can also be applied to the tree after pruning is completed. Like leaf blight, leaf spot can be pruned from trees and pruned branches and leaves should be destroyed. Cutting intertwining branches should be done to completely eliminate the disease. Fungicide can be applied to prevent leaf spot. Aside from digging out the tree, roots and all, and destroying it, there is little treatment available for verticulum wilt. Rarely does applying nitrogen-rich fertiliser eliminate the fungus that causes verticulum wilt.
Proper planting and care can prevent the spread of fungus causing diseases. The first step is to obtain pest and disease free plants. Be sure to purchase your tree from a reputable nursery. Plant the tree in well-drained soil and do not water it from the top of the tree, but at the soil level. Fertilise the magnolia tree regularly to prevent susceptibility to disease. Apply preventive fungicides.