Out back, behind the fence, we grow perennial yarrow plants for use as cut-flowers in floral arrangements. One year in late May or early June I noticed a foamy substance on my plants and it looked as though someone had spit on the foliage. I couldn’t imagine who would have done that since the plants are really in an out-of-the-way place. Then some one told me about the Spittle Bug (Cercopidae), also spelled Spittlebug, AKA, Froghopper.
Here is a bug that actually does very little damage to your plants but is very unattractive. The insect makes this foamy appearance by pumping its body and turning a liquid secretion into foam and then hiding beneath it. While the bugs do feed on sap from your plant, damage is usually minimal and populations are small so insecticides are not necessary. Spraying the foam off of the plants with a garden hose is simple enough or there is a home remedy of:
One half cup of diced hot peppers
6 cloves garlic
2 cups water
2 teaspoons liquid (lemon) soap
Mix and blend all of the ingredients (except the soap) and let stand for 24 hours. Strain, add the soap then, spray the entire plant after removing the spittlebug and its foam.