Quick identification of a tree disease can mean saving the tree with an appropriate treatment and keeping the disease from spreading to nearby trees. Identifying your tree type and then the disease type as parasitic (caused by a living organism) or nonparasitic (caused by age or environmental factors) is the first step in the process. You can then create an action plan to treat or remove your tree once you have identified the source of the issue.
Determine the type of tree by matching the identifying characteristics of a leaf from your tree with one either in a tree identification book available at your local library or on the Arbor Day Foundation website, which has a step-by-step online tree identification by location.
Call your local Cooperative Extension office, tell them the type of tree you have, and explain the symptoms. Or visit their website and attempt to diagnose the disease via their online resources.
Mail a fresh sample of a diseased part of your tree or an insect from your tree to your state's plant disease and pest identification lab, if your own research doesn't uncover the source of the problem. Send this in a crush-proof container.