I noticed pretty, tiny balls on the underside of most of our Live Oak (Quercus virginiana) leaves. Not all the leaves had them, but many did and many had a lot of them.

Oak Leaf Galls

I thought they were galls, but wasn’t sure, so I did a bit of reading. I was right; a gall is an abnormal swelling of the plant tissue. They can be caused by mechanical injury, insects, fungi, and bacteria. In the case of our oak leaves they are caused by Wooly leaf gall wasps. The galls contain the insect’s eggs.

You can read more about gall-making insects and mites here. Some galls are formed in response to specific secretions of chemicals from the insect, but others are formed just by the presence of the insect.

In most cases, they are not harmful to the trees, which is my main concern. They do not indicate that the tree is weak or somehow compromised.

Here’s a close up.

Oak Leaf Galls Close Up

I think they are quite pretty. These range in size from about 1/32 inch to about 1/8 inch. Their color is reddish, but varies quite a bit. They almost look translucent and they appear to have rough texture, but I didn’t touch them.