You described the telltale signs of spittlebug-isn't that an attractive name! These petite insects nest in a mass of protective bubbles. In spring they feed on plants by sucking fluids from leaf and stem tissue, but seldom cause intense damage. If you see only a few of them in your garden, don't worry about controlling them. If you dislike the looks of the frothy foam, blast it off the stem with a forceful spray of water. A liberal dusting of diatomaceous earth, available at garden centers, can control a large infestation of spittlebugs. Protect perennials, trees, and shrubs with a dormant oil spray, also available at garden centers, in early spring before leaves unfurl. The spray will prevent spittlebug eggs from hatching.