There’s almost nothing more disgusting for gardeners than finding their strawberry plants full of what appears to be spit just as the berries begin ripening. Although the foamy material is not spit in the truest sense, it still makes berry harvest less than appealing.
The white foam blobs so prevalent this time of year, on a host of plants in addition to strawberries, are produced by the immature or nymph stage of spittlebugs. These small insects are related to aphids. They get their name from the globs of foamy “spit” they create along the stems of plants. They produce the frothy mixture by mixing air with fluid excretions, but not out of their mouth so it technically isn’t spit.
The immature bugs feed face down on the stem, and as excess sap is pooped out, it is mixed with a substance secreted by epidermal glands. The substance enhances surface viscosity and stabilizes the foam to make it last longer. As the mixture is forced out of the abdomen under pressure and is mixed with air, it forms bubbles.
Some species can produce as many as 80 bubbles per minute. The spittlebug moves its abdomen up and down, and as the bubbles emerge, it reaches back with its legs and pulls the bubbles forward over its back. The foam serves a number of purposes, protecting the nymph from predators as well as providing insulation from temperature extremes and a high-humidity environment so the tender nymph does not dry out. Nymph feeding causes twisting of leaves and thickening and shortening of stems of fruit spurs. When this occurs, fruit yield is likely to be reduced.
Adult spittlebugs, sometimes called frog hoppers, are typically a pale green or yellow color. Spittlebugs overwinter as tiny white eggs in plant stems. The eggs hatch in early spring. Over the next month or two, the nymph feeds within its spittle, molting two to four times. The nymph finally molts to an adult in late summer, emerging from its froth. Adults continue to feed through the summer, migrating to new hosts as foliage dries out, but they are rarely noticed without the conspicuous spit. In late summer to fall, females lay overwintering eggs.
Depending on the species, spittlebugs feed on many types of grasses, weeds and other herbaceous plants. They are commonly seen on roses, chrysanthemums, Shasta daisies and goldenrod.
Spittlebugs generally cause little damage to ornamental plants, but many people are distressed by the appearance of the spit globs or don’t like getting wet from “bug spit” when picking strawberries. They are easily eliminated by using a strong stream of water to wash the froth away, exposing the nymph to predators or drying out. WSU entomologists recommend cutting all of the leaves off June-bearing strawberries after harvest is over to renew the foliage and remove egg masses.
Donald D. Tapio is the Washington State University Extension regional specialist for Grays Harbor and Pacific counties. He can be reached at 482-2934 or firstname.lastname@example.org.