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. It appears in spring at a time when the familiar call of cuckoos can be heard, but has no connection with the bird.

There are nine species of froghopper found in the UK. Some species such as the Common froghopper Philaenus spumarius feed on a range of plants others such as Aphrophora pectoralis feed largely on one group of hosts. More information and images of UK froghoppers can be found from British Bugs.   

• 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

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 was a partner in a collaborative project which had 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 was 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  capability to respond to an outbreak. The project was 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 UK and are part of the biodiversity a healthy garden ecosystem.

• Apart from producing the 'spit' these insects have little detrimental effect on plants and they are part of the biodiversity that healthy gardens support

• 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