What do woodlice eat?
By The Pest GuyLast updated
Decaying plant matter, mostly: rotting leaves, dead wood that has already started to break down, compost, and the algae and mould that grow on damp surfaces. They are recyclers. The one bit of living damage UK council pest guidance attributes to them is chewing plant leaves, and that is the extent of it.
The question underneath this one is usually whether they are eating the house, and the answer is no. Woodlice do not eat sound structural timber. They cannot do much with dry, intact wood, which is why a woodlouse on a dry joist is a woodlouse passing through rather than a woodlouse feeding.
What is true is more useful than the myth, and it runs the other way round. Because they feed on wood that has already begun to rot, finding a population of them on a joist end, a skirting board or a window frame tells you that timber is already wet and breaking down. They followed the decay in. They did not cause it. Treat that as a moisture finding rather than a pest finding and you are asking the right question.
It also explains where they turn up indoors. Woodlice are crustaceans and breathe using gills, so they need damp to survive at all. Under the sink, behind the washing machine, along the bottom of an external wall: those are the places that combine the moisture they need with the mould and decaying material they eat.
Which is why feeding is rarely the thing worth acting on. Woodlice do not breed indoors, so the ones you can see all walked in from outside. Clearing leaf litter, compost and stacked wood from against the outside walls removes the reservoir, and sealing the gaps they walk through removes the route.