Cuckoo spit

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

They carry a disease Xylella fastidiosa which has not yet been found in the UK.

There is a survey to identify the distribution of spittle bugs here https://www.brc.ac.uk/irecord/xylem-feeding-insects