That is absolutely a spittlebug nymph. There are several species of spittlebugs (a type of leafhopper/froghopper) and I can't tell you which this might be. Sounds like some insecticidal soap applications are in order; you shouldn't need anything stronger than that, but just plain water probably won't do the job.

Typically, we wouldn't worry too much about spittlebugs, but it sounds like this tree has more pressure than is healthy. They do damage plants by making slits in the plant tissue to lay eggs. Too many of them can be problematic.

Spray once with the insecticidal soap and observe the effects. You might not need to reapply.

Good for you for being a darned good detective!

They are Spittlebugs, the larva of the Froghoppers. As a rule they are not harmful to the plants they are on, just a bit unsightly. The foam protective cover around the Spittlebug can be knocked off with shapr water sprays which will then expose the wee larva to predators. Insectidcidal Soaps can be used on them, once the foam protection is removed, no sense wasting that on removing the foam. Sometimes that sharp water spray will also knock the larva off the plant so you need do nothing more.

Thanks Rhizo_1 and kimmsr - extremely helpful! This small tree has had the spittlebugs before and they decimated the leaves, perhaps because there were just so many of them. I will attempt to remedy and report back.

Kimmsr, the insecticidal soap application DOES remove the foam. AND gets the spittlebug nymph, all at the same time.

Rhizo, maybe, maybe not, sometimes but not always. However, why waste insecticidal Soap removing the protective foam when just plain water will do that and once removed the larva is in plain view and can more easily be sprayed with the IS? A bit more work, maybe, but immensly more effective and satisfying.

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!!!!