Those are wasp galls. The female wasp lays her eggs in the leaf surface, and the galls are formed of leaf tissue that shelters the growing larvae.

Not dangerous at all. The insects are *very* small and lack stingers.

Nothing is what you should do, this because the galls don't affect the trees health.

Maple gall MITES cause those galls, I believe, rather than one of the diminutive gall wasps.

Here is a link that might be useful: {{gwi:365461}}

Whichever insect caused the galls, any damage is purely cosmetic. The insects won't bother you at all, if you even notice them.

rhizo is right -- I was too lazy to look it up. I think the galls are attractive ornamentation.

;-) I've always thought that galls are very cool, too.

These bugs (maple mites) are not always harmless. Our neighbor lost his tree this year, after 4 years of infestation. Every summer his tree lost it's leaves, prematurely, and finally this year they just didn't come back. We too had a silver maple, with the same problem, but we decided to dig ours up this spring. I guess it depends on how bad the investation and/or how young the tree is? Anyway, if it's a tree you really want to keep, I would recommend spraying it this fall.

Not to contradict you, Gmaur, but I think your neighbor's tree must have had some other problem in addition to the gall mites. Everything I have heard or read says that they aren't harmful to the tree.

Here is a link that might be useful: maple gall mite info

Thanks for that, have always wondered what they were!

Thank you for the responses. After a closer look today, I thought maybe most of the galls were confined to one branch, which I could just prune, but it looks like they are all over the tree. I'll watch it closely!

dibbit,
You are correct, there may have been something else causing the leaf drop on these trees. However, nothing else was apparent. Both trees, the neighbors and ours, were young trees...approx 7-8 yrs old. I suspect the premature leaf drop, year after year, weakened the neighbors tree. Last summer,for the first time, ours dropped leaves prematurely too.

The link you provided does not mention the leaf drop, but other information does. Ortho says spray the trunk of the tree, spring or fall, when the mites are living in the tree trunk. Spraying the leaves doesn't help.

I noticed today I have the same problem above and it freaked me out! I have saved my tree now twice once in a ice storm and once in lets say lack of rain. It has always grown well and what I want to know is this going to damage any part of the tree what so ever? Does anyone know and is there a site i can visit? thanks for the help

Can nayone tell me what type effectively gets rid of the red galls on the leaves , And when is the proper time of year to spray these trees with this problem

I've had these bumps on my tree for at least 2 years (that I've noticed). They don't make for a pretty show in the fall. I've never seen a wasp in my backyard. I'm going to try to spray a basic hose end bug killer over it. Although as I was just Googling, I noticed that the picture you are all seeing (which looks IDENTICAL to my tree), SOUNDS more like a "Maple Bladdergall Mite". I guess that would make sense if I've never seen a wasp?

Great post, thank you - i was starting to freak out when i saw them on my trees

I too have this problem with my silver maple but my issue has been slightly different. My tree is in its' 7th year. It's been growing nicely but last year I didn't get a lot of leaves and early in the spring it produced a lot of seeds. Same this year. It does have leaves and they do have the red growths on the leaves, which I didn't notice last year. It had a ton of seeds again this spring which finally have fallen and it has very sparse leaves. Sometimes they appear all droopy. I am worried about losing this tree. It is in my backyard and I have quite a garden and all other plants, including a flowering crab apple tree and a Magnolia blossom are doing amazingly well. Any ideas?

Will something like Beyer imidicloprid (spelling??) systemic insecticide applied around the dripline in spring and/or or fall help control the mites?

We have 2 maples in our back yard right next to each other. One is about 50 years old and the other is about 35 years old. Both of our trees have these " bumps " on them every year. Our leaves never fall prematurely. As a matter of fact we normally have a few inches of snow on the ground before the trees lose the leaves. Its been lile this my whole life. My grandmother owned this house so as a child i climbed these trees all the time. My wife and i own it now and Im almost 30 now so its been going on for quite some time. I beleive they are harmless and we really dont notice them unless we look real closley. As long as a billion arachnids dont suddenly hatch and eat us alive im ok with them being there.

I have 7 maples in pots on my deck. I grew them all from seedling growing in the wrong place. They are about 5 years old and 4' or so. Every year they get the galls. The leaves get eaten by the mites but you don't see them. The tree grows new leaves and is fine. I still haven't used to being grossed out by it but I know it won't really do any long term harm.

Utterly inconsequential. The world is chock-full of problems. This isn't one of them.

And for the guy some years back wondering about using strong systemic insecticides for this issue, my scientific word for that would be "sheesh".