Woodlice Killer Sprays

At the routes in and the damp gaps they shelter in: door thresholds, around air bricks, along skirting, where pipes enter walls, behind and under sinks, and in cellars and utility rooms. Treat the edges and entry points rather than open floor - woodlice walk in from outside and travel along edges.

It depends on the product. Fast knockdown sprays act on the woodlice you can see. Residual products leave a deposit on treated surfaces that helps reduce repeat activity over time, provided the surface is one the label approves and it is not cleaned off. Our guide to knockdown, residual and IGR treatments explains the difference.

Follow the label on the individual product. Keep children and pets out of the area until treated surfaces are completely dry, ventilate as directed, and do not treat food preparation surfaces or anything a pet may lick or chew. Store the product out of reach.

Follow the reapplication interval on the label. In general, re-treat after cleaning or anything else that removes the deposit, and again if fresh activity appears. Do not increase the frequency beyond what the label allows.

A spray suits damp locations and gives faster knockdown on what you can see. A powder holds in dry cracks and gaps and keeps working while it stays dry - which is the catch with woodlice, since the areas they gather in are damp. In a wet cellar or around a leaking pipe, a spray usually does more.

Season and weather. Woodlice move indoors for shelter as outdoor conditions turn cold and wet, so autumn and winter is when most people notice them, and a spell of heavy rain will push a wave in at any time of year. A sudden increase is usually the weather rather than a failed treatment, and numbers normally fall away again in spring.

Because the source is outside. Woodlice live in leaf litter, compost, log piles and under pots and paving, and walk in through gaps at the base of doors, air bricks, cracked render and pipe entries. Spraying deals with the ones already inside and does nothing about the population outdoors or the gap they use. Seal the gaps and clear that material away from the wall. Check the gutters and downpipes too - a blocked gutter soaks the wall below and creates the damp strip they gather in.

Often not. Woodlice do not bite, damage sound timber or carry disease. Indoors they are usually a signal that there is damp and a gap, so proofing and drying the area does more than treating. For a cluster already inside, vacuuming them up and emptying the vacuum outside is quicker than any spray. Use a spray where numbers are persistent, or where they are getting well inside the house rather than staying near the door.

If woodlice keep appearing in numbers well inside the house rather than near doors and air bricks, the underlying problem is damp rather than pests, and a damp or timber specialist will usually be more use than a pest controller. If you do want pest control as well, look for a qualified pest controller with BPCA membership.