Ask Rosie

Leaf galls unsightly but usually not harmful

Posted on Jul 01 2015 in Backyard, Outdoors

gall1 WEBWe have a pin oak tree that is approximately 30 feet tall. On the north-facing side of the tree there are many wilted leaves, and there are many balls of strange growth. Can you help identify the problem and offer solutions?

— Mike and Lynn Wagner, Indianapolis

My best guess is one of the many leaf galls common to oak trees. Leaf galls are usually more of an unsightly cosmetic problem than a health crisis and do not warrant chemical control. The gall itself is primarily made up of plant tissue that forms when insects lay eggs inside the leaf tissue and either the adult or the developing young insects secrete a growth-stimulating substance. Each insect causes a very characteristic gall.

Once the gall appears, the appearance of the current growth cannot be remedied. More information regarding galls on trees is available in Purdue Extension publication E-56 at

Wilting could be a more serious problem at work. I encourage you to send samples of your oak tree to the Purdue Plant and Pest Diagnostic Laboratory for diagnosis. More information about submitting a sample can be found at

Rosie Lerner is the Purdue Extension consumer horticulturist and a consumer of Tipmont REMC. Questions about gardening issues may be sent to: “Ask Rosie,” Electric Consumer, P.O. Box 24517, Indianapolis, IN 46224, or