They appear to be flower galls off female ash trees. There are several species of tree affected by these mite induced galls.
Ash Flower Gall
This gall is caused by a small mite that causes irregular distortion of male flowers. The galls are initially green, then dry and turn brown. They are unsightly and remain on the tree over the winter. A dormant oil treatment may be effective. An application of carbaryl (Sevin) or chlorpyrifos (Dursban) in the spring when the first blossoms begin to form may be of some help.
Ash Midrib Gall
Normally 1/2 inch to 1 inch long, these galls are succulent and have thick walls. A small cavity within each gall contains one or more small maggots, the larval stages of very small flies called midges. Female midges lay their eggs in very young leaflets during early spring. Gall formation begins soon after the eggs are laid. Specifics of the biology of this insect are not known. The galls probably do not harm tree health.
The last two paragraphs were from:
Some Common Shade Tree Galls | University of Kentucky Entomology
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