How to Diagnose Magnolia Leaf Problems

Look at the entire plant or tree. If it is losing leaves when it shouldn't, or if it is losing them from the crown down and not evenly, the problem lies in the roots. Root issues sometimes occur when magnolias are transplanted, damaged by gardening tools, or affected by root diseases, many of which are caused by overly wet soil.

Check for insects. Leaves damaged by insects will often have holes in them or ragged margins. More important, the insects will usually be nearby. The magnolia scale, for example, is a half an inch long and easy to see with the naked eye.

Touch the leaves. Honeydew, a sticky substance secreted by many insects, primarily mealybugs, will be present on and around leaves infested by bugs. Ants are attracted to honeydew, and mold spores sometimes stick and grow on honeydew. For these reasons, the presence of ants or sooty mold are also indicators of an insect problem on your magnolia leaves.

Examine the leaves for spots. Most magnolia leaf diseases cause spots to develop on the leaves. The spots may range from small yellow dots to large, dark greasy patches. Some are caused by fungi, while others are caused by bacteria. Although unsightly, the spots don't usually pose a health threat to the magnolia, according to the website of the University of California Integrated Pest Management Program.

Note the color of the leaves. If they turn yellow or brown prematurely, the branch may be dying from either a gall -- a raised, bumpy growth on the wood caused by a bacteria -- or a canker, which appears as sunken, dead wood. Both will cause leaves to either die before they fully open or die prematurely, turning yellow, brown and dry.