What is cuckoo spit?

Cuckoo spit is a white frothy liquid secreted by the nymphs of a sap-sucking true bugs known as a froghoppers. They are also known as spittlebugs.

Symptoms

• Blobs of white frothy liquid develop on young stems and leaves of a range of plants in late spring and summer
• Each blob contains a creamy white insect nymph up to 4-6mm (¼in) long
• Usually plant growth is unaffected, but, if the nymph has been feeding at the shoot tip, this may cause some distorted growth

Froghoppers and Xylella

Xylella fastidiosa is a bacterial disease of a wide range of plants and causes symptoms including leaf scorch, wilt, dieback and plant death. It is causing serious problems in Southern Europe but it has not yet been detected in Britain. The disease is spread by insects that feed on the xylem of plants. This includes froghoppers. 

Xylella is not in the UK but could be introduced through the importation of infected plants. The RHS is a partner in a collaborative project which aims to understand and prevent the introduction of vector-borne plant pathogens, especially Xyllela, to the UK and the challenges they pose to the UK flora. The BRIGIT project has been funded by the Biotechnology and Biological Sciences Research Council, Department for Environment, Food and Rural Affairs, and the Scottish Government to reduce this risk and to increase our capability to respond to an outbreak. The project is being undertaken by scientists in ten UK research organisations led by the John Innes Centre.

Spittlebugs are not a pest, so please don't remove them; they are an innocent carrier of Xylella outside of the UK.

Control

• Apart from producing the 'spit' these insects have little detrimental effect on plants and should be tolerated as part of the biodiversity that gardens support
• If considered unsightly, they can be wiped off by hand or dislodged with a jet of water from a garden hose
• There is no need to use insecticide against froghoppers

Biology

• This froth has no connection with cuckoos
• It is secreted by the immature stages of sap-sucking insects known as froghoppers, presumably as a means of protecting themselves against predators and adverse environmental (weather) conditions
• The adult insects are present during mid-late summer and live openly on  plants. They do not produce cuckoo spit or cause any noticeable damage
• Overwintering eggs are deposited in plant stems in late summer