Anchorage Daily News

Q. What is causing the spitlike foam in my garden, and is it damaging my plants?

A. Children have come up with many wild and interesting guesses --from snake spit to rabid plants -- about the globs of white foam seen on roadside and garden plants in summer. The white mass of bubbles closely resembles whipped egg whites dripped on the plant and are most often found at the stem or base of a leaf.

The foam does not identify plants that have rabies, as I believed when I was a child. A small insect, called a spittlebug, makes the foam by blowing the bubbles out its rear end!

The source lies hidden under every foamy mass: a group of immature green, boxy insects enjoying the protective moisture that their homemade dwelling provides. The spittle nymphs, or younger insects, insert their piercing mouthparts into the plant, then suck the carbohydrates and water out like a straw.

Young spittlebugs remove so much water that most of it ends up being excreted with the digested nutrients from the plant juice. The bugs blow air bubbles from their abdomen into the sticky mix and then position the lather around them, creating a protective covering.

Unlike nymphs, the inconspicuous brown adults do not secret a foamy lather. The nymphs lack the hard exoskeleton enjoyed by the adults. As spittlebugs are slow, methodic feeders, they would be easy prey without their bubbled housing.

Spittlebugs are "true" bugs from the family Cercopidae, close relatives of leafhoppers, another Alaska plant eater whose damage is commonly seen by gardeners. Spittlebugs cause almost negligible damage and are frequently only an aesthetic issue. Often, no control is needed. In high numbers they may cause stunting or distortion in new growth, but this is uncommon.

If they become a problem, a strong jet of water will knock them off and disperse the spittle. Repeated spraying whenever the froth is observed should take care of your plants for the season. Turning over any infected material in the fall will also minimize populations next year, as the freezing ground will kill the overwintering eggs.

Spittlebugs are found throughout the U.S. and Canada, and their populations tend to fluctuate from year to year. The bugs will feed on a variety of plants, but in Anchorage, fireweed seems to be a favorite.

If you have spittlebugs in your garden, there is little cause for alarm. There are many more serious pests that could be devouring your plants.

Hailey Scofield works in the Integrated Pest Management program with the UAF Cooperative Extension Service in Anchorage. If you have questions regarding insect or pest problems, call 786-6300.

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