The white, foamy blobs appearing on plant stems and leaves in spring and early summer are not plant disease or spit, but the temporary home of a common garden insect. This distinctive mass is produced by the immature form of the insect, known as the spittlebug or froghopper. The frothy substance is created by the nymph stage, which remains hidden inside the foam while it feeds and develops.
Identification: The Nymph and the Adult
Spittlebugs belong to the Superfamily Cercopoidea, commonly called froghoppers due to the adult’s impressive jumping ability. The life cycle features two distinct forms: the nymph and the adult. The nymph is the stage responsible for the characteristic foam; it is a soft-bodied, wingless insect, often pale green or yellow, concealed within the spittle mass for protection and moisture retention.
When the nymph matures, it undergoes a final molt to become an adult froghopper that no longer produces foam. Adult froghoppers are stout, small insects, typically measuring about a quarter-inch long and varying in color from tan to brown or mottled gray. Their robust hind legs allow them to launch themselves significant distances when disturbed.
Why Spittle Bugs Create Foam
The foamy mass, often called “cuckoo spit,” is a byproduct of the spittlebug nymph’s feeding habits and is manufactured for survival. Nymphs feed by inserting their piercing-sucking mouthparts into the plant’s xylem tissue to consume sap. Since xylem fluid is highly dilute and contains low concentrations of nutrients, the nymph must process large volumes to acquire necessary amino acids, leading to the excretion of excess liquid.
This excreted fluid is mixed with a mucilaginous substance secreted from glands on the nymph’s abdomen, which increases the fluid’s viscosity. The spittlebug then introduces air into this mixture by contracting its abdomen and using specialized appendages to whip the solution into a stable foam. This structure serves three purposes: it acts as a physical barrier against predators, insulates the nymph from extreme temperatures, and prevents desiccation by maintaining a moist microclimate.
Impact on Plants and Gardens
The damage caused by spittlebugs in home gardens is generally minor and largely cosmetic, though they feed continuously during their nymph stage. They extract xylem fluid, which is responsible for water transport within the plant. Heavy feeding can occasionally result in minor stunting of new growth, slight leaf curling, or temporary distortion of the plant tissue.
The visual presence of the foam is usually the biggest nuisance, not a significant threat to the plant’s overall health. While froghoppers are known vectors for certain plant diseases, such as Xylella fastidiosa, this role is primarily a concern in commercial agriculture. For the average gardener, the spittlebug’s impact is minimal, and the plant typically recovers once the nymph matures.
Simple Management and Removal
Because spittlebug damage is rarely severe, chemical control methods are unnecessary and often ineffective since the foam shields the insect from topical pesticides. The simplest and most effective management strategy is physical removal using a strong, direct jet of water from a garden hose. This action dislodges the foam and the nymph, causing it to fall to the ground.
Once the nymph is washed off, it is exposed to dry air and predators, which significantly reduces its chance of survival. Repeating this hosing process every few days can effectively manage populations on ornamental plants and garden vegetables if the foam is deemed unsightly. In most healthy ecosystems, the spittlebug population is naturally kept in check by generalist insect predators.