White, frothy masses clinging to plant stems and leaves are a common sight in many gardens. Often called “cuckoo spit,” this peculiar substance is a natural phenomenon produced by a tiny insect. Understanding its origin can help demystify its presence on your plants.
What is Spittlebug Foam?
Spittlebug foam appears as white, frothy blobs resembling a dollop of spit or soap suds on plant stems and leaves. These distinctive masses are commonly found on a wide variety of plants, including ornamental grasses, roses, chrysanthemums, clover, and strawberries. The foam is not actually spit from the insect’s mouth, despite its common name, but rather a byproduct of the feeding process.
The creature responsible for this frothy display is the spittlebug nymph, the immature stage of an insect also known as a froghopper. These nymphs pierce plant stems and extract large quantities of plant sap, specifically from the xylem. As the nymph feeds, it processes the excess sap, which is then excreted from its anus.
This excreted fluid mixes with a special substance secreted by glands on the nymph’s abdomen, which enhances its viscosity and helps stabilize the foam. The nymph then introduces air into this mixture by rapidly contracting and extending its abdomen, creating numerous bubbles. The nymph uses its hind legs to pull these bubbles forward and completely cover itself in the frothy mass.
Why Spittlebugs Produce Foam
The production of foam by spittlebug nymphs serves several important biological functions, primarily protection and maintaining a suitable environment for development. The frothy mass acts as a physical barrier, camouflaging the nymph from predators. This makes it difficult for visually hunting predators, such as birds, to spot the tiny insect hidden within.
The foam also provides insulation against temperature extremes, helping to regulate the nymph’s body temperature. This protective layer prevents the nymph from overheating during hot periods and offers warmth during cooler temperatures. This thermoregulatory adaptation is important for the nymph’s survival and proper development.
Another function of the foam is to prevent desiccation, or drying out, of the soft-bodied nymph. The humid environment within the frothy mass keeps the nymph moist, which is essential as it feeds on watery xylem sap and expels large amounts of fluid. The foam ensures a stable, moist microclimate, allowing the nymph to develop safely through its various stages.
Effects on Plants
Gardeners often express concern about spittlebug foam, wondering if it indicates significant harm to their plants. While spittlebugs feed on plant sap, the damage they cause is typically minor and largely cosmetic, especially in home garden settings. The foam itself is not harmful to the plant.
Spittlebugs extract sap from the plant’s xylem, the tissue responsible for transporting water and minerals. Since xylem sap is less nutrient-dense than phloem sap, nymphs must consume large quantities to obtain sufficient nutrients for their growth. This feeding activity generally does not significantly impact the overall health, growth, or yield of most plants.
Severe infestations are uncommon, but in rare instances, a high number of spittlebugs might lead to minor stunting or distortion of new plant growth. For instance, on certain crops like strawberries, very heavy feeding, particularly during dry conditions, could potentially reduce yield or cause stunted fruit. However, for most ornamental plants and garden varieties, spittlebug foam usually does not warrant alarm.
Simple Ways to Address Spittlebug Foam
For those who find spittlebug foam undesirable, straightforward, non-chemical methods can remove it from plants. The most common and effective approach is to dislodge the foam and the nymph within it using a strong stream of water from a garden hose. This action washes away the protective frothy mass, exposing the nymph and potentially causing it to dry out or become vulnerable to predators.
Alternatively, the foam can be gently wiped away by hand from the affected plant parts. This manual removal is effective for smaller infestations or when a more precise approach is preferred. While these methods remove the visible foam, the nymphs may attempt to produce new foam if they remain on the plant or move to another suitable location.
It is generally not necessary to intervene, as the damage caused by spittlebugs is minimal and rarely impacts the plant’s long-term health. Given their benign impact, chemical treatments are usually unwarranted and not recommended for spittlebugs in home gardens. Focusing on these simple, non-toxic methods can help maintain the aesthetic appeal of plants without resorting to more aggressive interventions.