What do you see on the leaves? Aphids or Scale will be present when you look because once in place they do not move. If you don't see them they are not the cause, and seldom do Aphids or Scales munch through the leaves to leave holes.
If you cannot see anything that might be doing that and the holes do not appear to be affecting the health of the tree then there is nothing to do at this time. If and when the cause is identified then steps can be taken to control them if that is necessary.

"Bacterial canker is common west of the Cascades because it is favored by our cool, wet weather. Symptoms include infected buds that may fail to open in spring. Small, greasy-looking spots appear on newly opened leaves. The spots turn a dark brown and may eventually fall out, leaving a shothole appearance. In wet weather, the spots may expand and kill terminal shoots of susceptible cultivars. Chemical control is to apply copper products before fall rains, during leaf fall and in late dormancy just before buds open." WSU

Here in our very coolest and foggiest part of the state, weeping cherry almost always has problems (that led to me taking it out)....needs full sun with a site that gets plenty of air circulation to ensure disease free growth, great drainage. Those holes in leaves may very well be a fungal or bacterial leaf spot disease and not an insect at all. My own was always plagued with sawfly larvae (aka pear slug and one of the first to consider with weeping crab and cherry) but your photo doesn't show the 'window pane' holes in leaves.

I don't use any oils or pesticides for insect control as I grow organically. google Arbico. they specialize in beneficial insects. I ordered three praying manti egg cases. one for my yard and for my neighbors on both sides. one egg case hatches abou two hundred manti. They devour every insect you hate. and once they live out their life cycle they lay their own egg cases. so now I have an ongoing population of manti. I live an hour north of death Valley so its a desrt hot blazing summers freezing winters if my manti can stay alive year after year your area will support them as well. also consider Ladybugs these are literalyy the toughest bug in the pack they eat every single pest bug you can imagine problem is when they eat everything they move on to find more food. I even take my baby manti indoors to work over my bonsai and houseplants I leave a couple of windows open all the time for my cats to get in and out. so manti have an escape, or entrance if they choose. I grow vegetables, tobacco, fruit, housplants and bonsai. this was a permanent and inexpensive solution to my bug problem. Good Luck!!!!