Apply other materials when crawlers appear and repeat in 10 days. As with all pesticides, read and follow all label instructions and precautions. Maples often develop irregular growths or swellings known as galls on their leaves. Each insect or mite produces its own distinctive gall shape. Often the distinctive shape allows for identification of the pest.
Galls typically develop in spring at about the time that leaves are expanding.
Once the gall forms, the pest is protected inside the structure. When homeowners see these growths on the leaves of their maples, they often become quite concerned. It is important to remember that while unsightly, they do not cause permanent injury to a tree. If a tree is small, the homeowner can handpick and destroy leaves before exit holes form to allow the release of the pest. This problem occurs when a root entwines around another large root or the base of the tree and prevents or hinders water and nutrient movement.