Cuckoo Spit is a minor pest that affects lavender in Scotland. Here is what it looks like, how to spot the damage, and which controls have been tested.
What does it look like?
Blobs of white frothy liquid on young stems and leaves, usually appearing from spring into summer. Each blob hides a single creamy white nymph up to 4 to 6mm long, the insect that made it. Lavender is far from the only host: chrysanthemum, dahlia, fuchsia, rosemary, rose and willow are among the other plants it turns up on.
Is this pest active now?
The froth is a spring-and-summer sign: nymphs produce it roughly May to July. Once nymphs mature into adults in mid to late summer, the spit stops appearing, even though the insects are still around on the plant.
Symptoms
Plant growth is usually unaffected. If a nymph happens to be feeding right at a shoot tip, that can cause some distorted growth, but that’s the exception rather than the rule. The froth itself does no harm.
Life cycle
Adults lay overwinteringKeeping a plant alive and intact through the cold months, whether left outdoors, moved under cover, or stored dormant. Full definition → eggs in plant stems during late summer. Those eggs hatch the following spring, and it’s the nymphs, not the adults, that secrete the white froth. Adults themselves live openly on plants through mid to late summer, producing no spit and causing no noticeable damage despite being sap-sucking insects.
Why this matters in Scotland
Froghoppers are a known vector for Xylella fastidiosa, a serious bacterial plant disease causing real damage in Southern Europe. Xylella isn’t established in the UK, but the Scottish Government was one of the funders, alongside Defra and the Biotechnology and Biological Sciences Research Council, of BRIGIT, a UK research project working to understand and prevent its introduction.
A genuine Scottish stake in the wider biosecurity picture behind an insect most gardeners assume is only a cosmetic curiosity.
Controls: what actually works
All the methods below are backed by real evidence, not just repeated folklore.
Leave them alone
The simplest control there is: do nothing. There’s no real benefit to removing them, and it takes away part of the garden’s biodiversity for nothing in return.
Myths about cuckoo spit
3 common claims about cuckoo spit, checked: 1 busted1 disputed0 untested1 hold up
“Cuckoo spit means the plant underneath it is being damaged or infested by a harmful pest”
Plant growth is usually unaffected by the froghopper nymph hiding inside the foam, with distorted growth only turning up in the rare case a nymph happens to be feeding right at a shoot tip. A US university extension entomology factsheet on meadow spittlebugs likewise describes the direct feeding harm to the host plant as minimal and treats large populations as something that rarely needs intervention. Cuckoo spit is a sign of a common, mostly harmless insect, not a symptom of plant damage.
What to do: Leave the froth and the nymph inside it alone, the froth's presence on its own is not a reason to treat the plant for anything.
2 sources
- RHS: Cuckoo spit and spittlebugsPlant growth is usually unaffected by spittlebug nymphs, with distorted growth only an occasional exception when a nymph feeds right at a shoot tip.
- UConn Cooperative Extension IPM Program: Meadow SpittlebugsSpittlebug feeding causes minimal direct harm to host plants, and large populations do not by themselves signal a systemic pest problem needing control.
“You should hose or wash cuckoo spit foam off plants to protect them”
RHS guidance is explicit that spittlebugs should not be removed at all, treating them as a beneficial part of garden biodiversity rather than something to wash away. A US university extension IPM programme covering the same insect takes a more control-oriented line elsewhere in its literature, describing spittlebugs as generally manageable and rarely worth aggressive intervention, without recommending routine washing as standard practice either. Neither source frames hosing off the foam as necessary for protecting the plant.
Our read The washing habit likely persists because the foam looks like something is wrong. Since the RHS source found no plant harm from the nymph itself, there's nothing for washing to prevent.
What to do: Don't bother hosing it off for the plant's sake, there's no protective benefit. If you want it gone for purely cosmetic reasons a jet of water will dislodge the nymph without harming the plant.
2 sources
- RHS: Cuckoo spit and spittlebugsSpittlebugs are not a pest and should not be removed, they are part of the biodiversity a healthy garden ecosystem supports.
- UConn Cooperative Extension IPM Program: Meadow SpittlebugsSpittlebugs cause minimal direct plant harm and are generally manageable insects that rarely require intervention.
“The insects that produce cuckoo spit can carry and spread the plant disease Xylella fastidiosa”
The common froghopper behind cuckoo spit is a recognised Xylella fastidiosa vector. Outside the UK, spittlebugs are an innocent carrier of Xylella, and the meadow spittlebug is the principal insect spreading the disease in Italy and France. Xylella fastidiosa itself is not currently established in the UK, so today's cuckoo spit in a Scottish garden carries no disease risk; the concern is about a future introduction via imported infected plants rather than anything happening in UK gardens now.
What to do: No action needed on cuckoo spit in your own garden for disease reasons, this isn't a case for removing it. The actual precaution is buying plants from reputable, biosecurity-compliant nurseries so infected stock isn't imported in the first place.
In Scotland: This is the reason spittlebugs are tracked in Scottish-linked biosecurity monitoring as part of the BRIGIT surveillance project, rather than being purely a cosmetic curiosity.
2 sources
- RHS: Cuckoo spit and spittlebugsSpittlebugs are an innocent carrier of Xylella outside of the UK; Xylella is not in the UK but could be introduced through the importation of infected plants.
- Defra UK Plant Health Portal: Xylella fastidiosaThe widespread and common meadow spittlebug is the principal insect spreading Xylella fastidiosa in Italy and France, and the disease is not known to occur in the UK.
Frequently asked questions
What should I do first if I find cuckoo spit in my garden?
Start with leave them alone.
Will cuckoo spit kill my plants?
They rarely kill established plants. The damage is usually cosmetic on outer leaves, and natural predators often bring numbers under control without you doing anything.
When are cuckoo spit most active in Scotland?
Check the seasonal activity section above. Scottish timings can run a few weeks behind the UK-generic figures.
Should I just leave cuckoo spit alone?
In most gardens, yes. cuckoo spit are food for birds, wasps and predatory insects, and a healthy garden carries some without trouble. Tolerance is also RHS's official position now, for that same reason.
Sources
1 source, recorded with what each was used for
- RHS1: identification, symptoms, life cycle, active timing, tolerance guidance, Xylella vector risk and the BRIGIT project