Galls are growths on the plant which may be caused by fungus, bacteria, insects, mites or mechanical injury. Visually the tree or shrub will show swelling in portions of the leaf, twig, trunk, root or branch. This section will cover galls caused by insects or mites on the plant (for some galls caused by fungus, click here). Galls (due to insect activity) are caused by one of two reasons: The insect feeding on the plant or the insect laying eggs on the plant. It is important to note that the insect itself does not form the gall (nor can galls be formed on matured growth), the gall is formed by the tree or shrub reacting to the insect activity somewhat like a rash or other reaction humans might generate when certain insects bite or sting them.

Although the damage is unsightly, galls do not typically damage the tree in the long run (though heavy infestations can defoliate and deform a tree). Once the gall has formed, it can not be cured though homeowners may prune the gall out. If galls are a common problem year after year, an insecticide may be warranted as a preventative measure (the application must be made through spring into early summer).

Trees and shrubs Attacked: May occur on nearly every species of tree or shrub in the Northwest Ohio or Southeast Michigan region.
Maple Bladder Gall Damage to look for : Swelling of new growth on the tree Abnormal growths on the plant Usually, galls are colorful and standout.