Hi Pam,

My name is Ann Chanon, and I am an Agriculture and Natural Resources Extension Educator for Ohio State.  Thank you for your excellent pictures.  Your tree is an elm, most likely an American elm.  This is a common problem on our native elms this time of year; they are called elm sack galls and are produced by a non-native European aphid, Tetraneura ulmi. If you were to open one of these sacks you would find a large number of aphids feeding inside.  The winged aphids will emerge from elm galls in mid-summer where they will fly off to various grass plants and feed on the roots. Some years we see more of these sack gall aphids than other years. Fortunately, these aphids and the galls they produce do not cause significant injury to the overall health of the elm tree host. The aphids are preyed upon by minute pirate bugs, hover fly maggots, predaceous caterpillars, and birds, and these predators typically keep the population in check. Usually by the time the sack galls are discovered on elms, it is too late for a pesticide application to "undo" the galls. No treatment is needed.

Here is an article from our horticulture team about this insect https://bygl.osu.edu/node/1586

You are most welcome. Being vigilant about our trees is the best way to protect them from new and invasive pests and disease.  Thank you for contacting Ohio State University Extension.  Please reach out to us if you questions in the future.