Methods drawer
Residual treatments
A spray that stays active on a surface after it dries: useful at thresholds and harborages, wasted as a ritual, and harmful when it fights the bait.
A residual treatment is an insecticide applied to a surface — a foundation band, a baseboard crack, the underside of a deck — that keeps killing insects that cross it for days to weeks. Used surgically, residuals guard entry points against occasional invaders, protect a sill during termite work, and knock down exposed harborages.
Where they earn their keep — and where they do not
- Earn it: targeted crack-and-crevice work, exterior thresholds in the invasion season, and treatment of a located harbor.
- Waste it: calendar spraying of a whole interior with no identified pest, baseboard rituals for a problem that lives in the walls, and any spray over or near bait placements.
- Risk it: drift and runoff outdoors (keep treatments off flowering plants where pollinators feed, and away from water — this is a lake watershed), exposure of children and pets to wet surfaces, and the quiet selection of resistant roach populations.
Every residual is a labeled pesticide: the label's rates, sites, and precautions are law, 'more' is illegal as well as counterproductive, and a treatment you cannot name — product, place, target pest — is one you should not have paid for. Ask. A competent applicator answers without hesitation.