Ask a Master Gardener: Spittle bugs common here

Published 5:00 pm Monday, June 22, 2009

Question: Many of the plants in our garden have little white foam blobs on them that look like spit. What’s causing these? 

Answer: These white foam blobs are produced by the immature or nymph stage of the spittlebug, which are small insects related to aphids. These small insects 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 that 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, spittle bugs feed on many types of grasses, weeds and other herbaceous plants. They are commonly seen on roses, chrysanthemums, Shasta daisies and goldenrod. 

Spittle bugs 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.

Question: All of a sudden the leaves on our tomato plants have started to roll. We have carefully examined the leaves can cannot find any insects present. What causes the leaves to roll?

Answer: Leaf rolling on tomato can often occur due to a variety of reasons and does not affect yield. It can be caused by too much or too little moisture, excess fertilizer, heavy pruning, root damage during cultivation, or damage from herbicides. Most often the lowest leaves are the most symptomatic and they may eventually become thickened and leathery. This condition is most common in staking varieties whereas bush varieties seem to be less susceptible to environmental changes. It’s important to know what is causing leaf roll so that pesticides are not applied unnecessarily. If all of the plants in the garden have the same symptoms, it is most likely one of the causes mentioned above. Providing even, regular watering, and a balanced fertilizer should help to minimize leaf rolling. Applying a two-inch mulch of grass clippings around the base of the plants is an easy way to maintain soil moisture.

EDITOR’S NOTE: For answers to local gardening questions go to www.pnwmg.org or call 360-249-4125, the WSU Extension office in Elma, or call Rachel Gana at 642-8723 or acornwp@yahoo.com.