Are you noticing green, red or black bumps on your maple tree leaves? Are there small lumps, spiny bulges or apple-like growths on your oak tree? How about green and purplish brown nipples on the leaf surface of your hackberry tree? Galls are commonly found in Illinois, affecting maple, oak and hackberry trees, plus many other tree and shrub varieties.

Galls on tree leaves can be caused by a number of things, but most often they develop as a result of an insect feeding or other insect activity. About 95 percent of galls are caused by aphids, midges, wasps or mites and the remaining gall types are caused by fungi or other organisms. The gall that appears on the tree or shrub is not the insect, but actually plant tissue that has become irritated from insect activity or other factors. Galls are believed to form from plant-growth regulating chemicals produced by the parasitic insect.

By the time galls have formed and are noticeable, treatment is usually not effective. The insect causing the galls is protected from any chemical control. While often unsightly, most galls do not harm the tree or affect the health of the tree. There are spray application options that may be recommended for severe infestations, but this must be done early in the season before gall formation. Illinois is home to some oak tree gall types that may debilitate both young and old trees; especially when the gall begins to develop on tree twigs and branches. Promoting general health of the tree will help alleviate gall infestations. Fertilizing and watering during dry periods are important tasks homeowners can do to help their trees and shrubs.

Think you have galls on your tree? Contact the PHC Department to have your tree evaluated by a certified arborist. The certified arborist can provide recommendations and diagnosis information to help you help your trees.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Kramer Tree Specialists

Event Sign Up Form

%d bloggers like this: