What Are the Causes of Dull Magnolia Tree Leaves?

Algal Leaf Spot

• Normally a dark, shiny green on the upper surface with hints of light green or silver on the lower surface, magnolia leaves are subject to diseases that can turn the foliage of the tree dull. Algal leaf spot of magnolia is caused by a parasitic alga commonly referred to as "green scurf". The spots develop as gray or brown lesions on the leaf that proceed to wither and kill leaf tissue. The magnolia leaves then yellow and prematurely defoliate the tree.

Magnolia Scale

• The Magnolia scale (Neolecanium cornuparvum) sucks fluid from the tissues of the magnolia, depriving it of the water and nutrition the tree requires for vitality. As a result, dull magnolia tree leaves may come to pass. The insect overwinters on the tree then clusters together on the branches to feed with the coming of spring. The scale are covered with a white, waxy substance and excrete their waste -- honeydew -- which then turns into a black, sooty mold.

Scale Management

• The typical shine of the magnolia leaves are diminished with this black, sooty mold and scale infestation is typically unnoticed until the mold develops. Biological control of scale includes introduction of its natural predator, lady beetles. Branches that are covered with the sooty mold and scale can be pruned away, while chemical control includes introduction of a horticultural oil in late fall or early spring as a means of decimating the overwintering crawlers before they mature and feed.

Environment

• Approximately 80 species of magnolia exist, some native to specific areas and with their own environmental demands. Should a particular species be culturally deprived through weather, water or soil, the glow and health of the leaves may suffer. generally, most magnolias appreciate rich, well-drained, acidic soil with a pH level ranging from 5.0 to 6.5. The majority of magnolias are able to tolerate moderate drought. Gardeners should watch for signs that the roots are girdling -- strangling -- the tree as this harms all aspects of the magnolia's vibrancy.