[Stonehenge]

I've never seen this before, but found it pretty interesting. This leaf is from an otherwise healthy Maple - full leaf-out, foliage looks good (except of course for these growths). The affected leaves do not appear troubled with the growth except where there are many clustered growths. Those leaves have become curled and distorted.

The underside of the leaf is unremarkable - a small, light brown spot where the individual "nodes" are growing, outlined with a light halo around the brown spot.

The pic below is the first of two.

Any guesses at what this is? (I'm calling it a quiz, but the quizzer doesn't have an answer, so everyone gets an "A".)

[Stonehenge]

Here's a closeup of a few of the growths:

[Stonehenge]

Here's one with a larger cluster of growths:

[Hamons]

looks like a biore strip

actually -- its probably a gall... a growth caused by an insect or mite laying eggs in the leaf tissue. Usually jsut a cosmetic nuisance -- although can lead to leaf loss.

[dan deutekom]

It looks a lot like Maple Gall Mite to me although usually the galls are a reddish colour. We have it a lot in our area. It does very little real damage to the tree.

[dan deutekom]

Did a little looking in my books and it is either maple spindle gall caused by the mite Vasates aceriscrumena or maple gouty vein gall caused by the midge Dasyneura communis.

Although it is unsightly they do not cause large damage to the trees.

[Stonehenge]

It also seems to only be affecting the lower branches of this mature tree.

Thanks for taking the time to look into this - I appreciate it.