What are the pellets falling from oak trees?

Asked October 15, 2013, 6:33 PM EDT

Can you tell me what the tiny, beige-to-green dots are under the oak leaves this time of year? My yard has mostly white oaks and my roof and sidewalks are covered with these poppy-seed-sized pellets that are dropping off the underside of the leaves. The ants are carrying them away, so I'm thinking they might be eggs -- moth/caterpillar eggs maybe?

Montgomery County Maryland

4 Responses

These are insect galls. We get this inquiry occasionally and just had another one today. Normally, the galls fall to the ground still attached to the leaves, but sometimes they also separate and you get the rain of galls you are experiencing this year..
No cause for concern. There is no impact on the tree. Here is the page in our Plant Diagnostic which addresses leaf galls on shade trees: http://plantdiagnostics.umd.edu/level3.cfm?causeID=1165

ECN

Hmmm, that doesn't seem to quite fit what I'm seeing. The galls in the photo your answer links to are about 100 times larger than the tiny dots on my leaves and patio. Mine are the size of poppy seeds, not green pepper seedsk and there are millions of them (literally millions) scattered around my yard. Here is a photo of some leaves and the dots on the ground in my back yard.

Thanks for the excellent photo. There are hundreds of types of galls and perhaps that many that will select oak trees. The tiny 'poppy seeds' on your lawn and under the tree are, indeed, galls, and probably produced by a tiny, harmless wasp. This type of leaf gall does not harm the tree.
LS

Thanks!