In June I generally get phone calls and e-mails from homeowners claiming their shade tree is “dying or diseased” because it has “pimples” all over the foliage. Well don’t go running for the Clearasil even though it is not a “figleaf of your imagination” that your tree appears to have acne.
Your tree is not dying and it will survive this case of bad complexion. The bumps or “acne” are a gall caused by a tiny mite-like insect. The insect overwinters in the cracks and crevices of bark and branches. Very tiny and not visible they inhabit newly emerged foliage to feed and develop inside their new little home, the deformity caused by their habitation called a gall. We tend to see the worst cases in soft maples like Silver Maple or in Oak trees. Don’t worry about it, in extreme cases it could inhibit the photosynthesis process of the tree, but your tree is not going to die. It will just have to live with some good natured teasing from other landscape plants about it’s pimples. You can help out the tree by keeping it as healthy as possible by doing an annual feeding and making sure that if heat combined with drought occurs this summer you water the tree well. These problems tend to be somewhat cyclical in nature. You could use an Imidicloprid drench once a year at the base of the tree to help alleviate the symptoms but again, nothing to lose your “composture” about. Just marvel at nature and may the “forest” be with you.