Q: In my oak trees, I have these round balls attached to the stems and some leaves. What are they?

 

A:  You are referring to oak galls. They look like miniature golf balls on the tree. Over a period of years, it can literally cover the tree. Galls can be on many species of shade trees. Sometimes the galls will be on the stems and at other times on the leaves. They can be large, the size of a quarter or so, or may be just small bumps on the leaf. Each plant species will have its own type of gall.


Q: In my oak trees, I have these round balls attached to the stems and some leaves. What are they?
 
A:  You are referring to oak galls. They look like miniature golf balls on the tree. Over a period of years, it can literally cover the tree. Galls can be on many species of shade trees. Sometimes the galls will be on the stems and at other times on the leaves. They can be large, the size of a quarter or so, or may be just small bumps on the leaf. Each plant species will have its own type of gall.
A gall is a reaction by the plant to the insertion of insect eggs and ultimately larvae growing inside. You must control the adult insect to stop this. By the time you’ve seen the galls, it is too late to treat. Malathion or a dormant lime sulfur spray may be used in early spring at bud swell, bud break and again when leaves are half-grown to help reduce gall problems. Catching galls the first year and applying control that next spring before the tree gets infested is recommended. Besides looking unsightly, eventually this can kill your tree.
For more information, contact the OSU Extension Center, 14001 Acme Road, corner of MacArthur and Acme Road in Shawnee, or call 273-7683.