Spittlebugs

The larvae of the Froghopper, Spittlebugs produce the frothy spittle to keep themselves moist and to protect themselves from predators. The larvae suck sap and may cause leaves to wilt, but aren’t usually a serious pest. If you want to remove them then spray with a jet of water.

Image: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org