How often should you spray the outside of your house for bugs?

Short answer

Treat the exterior for pests every 3 months. In a cold climate the winter treatment can be skipped, since insects aren't moving. The treatment is a band of insecticide sprayed along the foundation, around doors and windows, and under the eaves, which stops ants, spiders and the rest before they get inside. It takes 30 to 60 minutes and $20 to $50 in product. A pest company charges $50 to $150 per quarterly visit.

Why it matters

Bugs come in from outside, and the way to keep a house clear of them is to stop them at the wall. A perimeter treatment puts a barrier where insects cross, so ants that would have followed a scent trail into the kitchen turn back at the foundation and spiders that would have set up in the corners of the porch don't. Treating outside also means little or no spraying inside, where the family lives.

The treatment wears off. Rain, sun and soil break it down over a few months, which is why the schedule is quarterly. Let it lapse and the first warm spell brings the ants back, and ants are the easy case. Wasps nesting under the eaves, carpenter ants in damp trim, and the mice that follow the insects in are harder to deal with once they're established. A spray every season keeps the pressure off.

When to do it more often

The index's modifier goes the other way: in a climate with a cold winter, skip the winter treatment, since nothing is crossing the barrier. Everywhere else, and in every other season, quarterly. The reasons to add a treatment are the signs below, and a few situations: a wet spring that brings ants in numbers, a new mulch bed against the house, which insects love, and a neighbor's treatment, which can push pests toward you.

What you need

A pump sprayer, sized for the job and kept for insecticide only
A perimeter insecticide labeled for outdoor use around homes, mixed as the label says
Sealant, a tube of exterior caulk or expanding foam, for the gaps you find

Steps at a glance

Walk the house and seal the gaps you find: around pipes and wires where they enter the wall, under siding edges, and around vents.
Pull mulch, leaves and stored items back from the foundation so the spray reaches the wall.
Mix the insecticide in the sprayer as the label directs, in the amount you'll use.
Spray a band along the foundation, up the wall a short way and out onto the soil, all the way around the house.
Spray around every door and window frame, under the eaves, and around the garage door.
Knock down any wasp nests and spider webs you find, and let the spray dry before pets or children go near it.

You're done when there's an unbroken band around the house, the frames and eaves are treated, and the obvious gaps are sealed.

Signs it's overdue

Ants or spiders showing up inside.
Wasp nests under the eaves or in the corners of the porch.
Droppings near the foundation or the garage, which mean mice are following the insects in.
Gaps around pipes and vents where they enter the house.

DIY or pro

This is an easy job with a pump sprayer, and the sealing is where most of the benefit comes from. A gap around a pipe is a highway, and a tube of caulk closes it for years. The spraying is the easy part, and the product sold for homeowners is effective if it's applied as the label says.

A pest company charges $50 to $150 per quarterly visit and brings a wider range of products, a sprayer that reaches the eaves, and a technician who notices the carpenter ant trail or the rodent gap that you'd walk past. That's good value for a house with a persistent problem, for anyone who'd rather not handle insecticide, or for a property with the kind of pest pressure a wooded lot brings. For a house with the occasional ant, the sprayer and the caulk are enough.

Safety

Chemicals: insecticide is poison, measured for insects but not harmless to people and pets. Wear gloves and long sleeves, mix outdoors, don't spray on a windy day, keep the spray off vegetable gardens and away from water, and keep children and pets off treated areas until the spray has dried. Store the product locked away and follow the label, which is the law for pesticides.

FAQ

How often should pest control be done outside?

Every 3 months, with the winter treatment skipped where winters are cold. The barrier wears off in a few months, so the schedule follows the seasons.

Is it worth spraying the outside of the house for bugs?

Yes. A perimeter treatment stops most insects at the wall, which means less spraying inside and fewer surprises in the kitchen.

What's the best time to spray for bugs outside?

Early spring, before insects become active, then every 3 months. Spray on a calm, dry day so the product dries where it lands.

Do I need professional pest control?

For a house with the occasional ant, a pump sprayer and some caulk are enough. For persistent problems, wasps you can't reach, or rodents, a pest company earns its quarterly fee.