Ever seen a blob of foam on a plant and wondered how it got there?
The frothy spittle, sometimes called cuckoo spit, is actually a telltale sign that an insect known as the spittlebug is feeding on a plant.
Scientists are calling for thousands of volunteers to help record sightings of spittle and spittlebugs across the UK.
The information will be used to map the distribution of the insect, in a pre-emptive strike against a deadly plant disease.
Xylella has struck several EU countries, blighting olive groves in southern Italy. The UK is clear of the disease but is on high alert.
There are a huge number of plants the Xylella bacterium could affect, from garden plants like the rosemary and lavender to the oak, said Dr Rebekah Robinson, senior plant pathologist at the Royal Horticultural Society.
"Xylella has 563 different host plants worldwide, so it affects a huge range of different species," she told BBC News.
"One of the really devastating things that could happen is that it could actually affect our native tree species as well, things like oak trees, a number of different ash species, sycamore – key plants in our landscape."
Scientists are calling for volunteers to record where and when they've seen spittle or spittlebugs, in gardens, meadows, grasslands and woodlands.