I looks like a "red pea" gall....these are formed by insects.
Some years are worse than others. It's G&B (Grin and Bare It).
I also tend to lean towards gall. But being who I am, have you pulled any of them off to see what is inside? Also send the photos to co operative extension in your area.
Maybe this will help, there were several varieties of gall listed on the web page, with pictures.
I see it on southern pecan trees I am curious to know what it is too!
I googled the photo for you and found this:
"Life in the garden takes many shapes and sizes but one of the strangest is galls. Galls are abnormal growths on a plant caused by a parasite.
I found these galls on a fallen oak leaf today. The doughnut shaped ones are Silk Button Galls (Neuroterus numismalis) and the green-coloured ones are Common Spangle Galls (Neuroterus quercusbaccarum). They are tiny. The diameter of the Silk Button is about 3 mm.
They are created when the tiny Cynipid wasp lays eggs on the oak leaf. The grub matures inside the gall." from http://english-country-garden.blogspot.com/2009/10/silk-button-and-common-spangle-galls.html
I have also seen it here in western PA and have no idea what it is.
I have these but the weird part is I can't figure out where they are coming from because the leaves don't match any of my trees
The bumps are harmless insect galls growing on the leaves. The galls are caused by pecan phylloxera, aphid-like insects that emerge in spring and infest leaves and twigs. Big populations of this insect can cause loss of the pecan crop for the current year and also the following year.
If you only enjoy your tree for its foliage and not the nuts, nothing needs to be done. Phylloxera populations vary widely from year to year, depending on weather and predators.
Thank you all. So follow up question is do we just ignore them and the winter will / SHOULD kill them off, or should we have the woods behind our house sprayed?
its a scale insect.
Jim, I wouldn't spray. I could be five years before you see it again.
@ Doug: Thank you, as always! If this is only a once every few years and they aren't doing any harm, we can just live with them. I haven't seen any insects or anything, so maybe the other insects and animals are eating them!
we had this on our maples in central Mich. We were told that it was insect galls and not to do anything. Probably wouldn't reoccur the next year, and they were right.
@ Pam: and ODD thing is these are ONLY on ONE type tree (leaves), all other trees in the yard are free of these things!
Jim this is not as odd as you may think...many bugs have host / parasite relationships with single species.
Stem rust is a disease that has an "intermediate host"
Getting rid of only one part of the cycle generally helps control the situation
@ KMSD: thanks....
Looks like Leaf Galls
haven't seen these this year, until today.. just a few leaves, but that means they are back...