Aphids on elm tree near garden

Through my Google searches I believe I have aphids on an elm tree near my garden. I know I have been battling them on my kale and trying to spray them off with a water bottle. Is there some sort advice that I should be doing to the elm tree in order to keep them from going between the tree and the garden.

Picture are the strange growths on the elm tree that I think suggests aphids.

Those projections on the leaves are called galls. Bacteria, viruses, fungi, insects, and mites can all 'hijack' plants to create these combination food/house structures. But they each are caused by a fairly specific combination of one of these organisms and a small range of host plants, and each creates different, recognizable galls.

There is an aphid that causes a gall on elm, called Elm Cockscomb Gall. But your galls looks like Elm Pocket Gall, caused by a mite:
http://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/elm-pocket-gall.pdf

This doesn't mean your elm tree doesn't have aphids, it probably has a least a few. But there are many types of aphids. Each kind has a limited number of food plants that they prefer or require. The kinds of aphids that like kale and other brassica plants aren't likely to also enjoy elm; they are pretty distantly related plants. I don't think you need worry about the aphids going back and forth between the kale and the elm.

Thanks beetles. I believe you are correct. I also noticed some clusters that were pretty clearly wooly elm aphids, and thought the galls (new word of the day!) Was connected.

I read that the wooly aphids go back and fourth between the elm and a secondary host. Since I was fighting aphids on my kale I assumed it was a possible secondary host. I was wrong, as you guessed. A second source wooly aphids stated their secondary host is a serviceberry. Which are also in the neighborhood. So asides from the unsightlyness, the elm aphids aren't a problem.

Thanks for the new word and calming my fears!

You're welcome! The different aphids, different plants thing is a recent sub-conscious to conscious epiphany for me. I realized it had to be the case after seeing aphids on plants used for anti-aphid sprays -- like garlic. How can garlic both be a repellent and a host? Oooh, different kinds of aphids with different preferences/tolerances...