Exterior barrier spray that kills spiders and the insects they feed on around your foundation, window wells, and garage.
Spiders are part of life along the Wasatch Front. Most are harmless. But finding them in your basement, window wells, or garage is not something any homeowner wants to deal with regularly. We apply a residual barrier spray to the exterior entry points spiders use to get inside. The treatment kills spiders and crawling insects on contact and continues working for up to 45 days. A single application can address an immediate problem. The four-treatment Exterior Spider Barrier Program keeps protection in place from spring through late fall.
Six spider species account for almost every encounter Davis County homeowners have. Only one is medically significant. Knowing which is which helps you decide what level of treatment your home needs.
The western black widow is the only dangerous spider in Davis County. It is shiny black with a red hourglass marking on the underside of the abdomen. Black widows prefer dark, undisturbed spaces. Window wells are the most common nesting site along the Wasatch Front. They also build tangled webs in garages, under porches, in stacked firewood, and inside block walls. Bites are painful and require medical attention, but fatal outcomes are extremely rare. Most bites happen when handling firewood or cleaning garages.
The hobo spider is the most common spider submitted to USU’s diagnostic lab. It builds funnel-shaped webs at ground level in window wells, foundation cracks, rock landscaping, and retaining walls. Males wander indoors from August through October looking for mates. They are poor climbers, which is why they end up in basements, bathtubs, and on floors rather than on walls or ceilings.
Here is what the current science says: hobo spiders are not dangerous. USU Extension states there is no significant scientific evidence that hobo spider bites cause necrotic (flesh-eating) wounds. The CDC removed hobo spiders from its list of venomous spiders of public health concern. The old common name “aggressive house spider” came from a misinterpretation of the Latin species name, not from actual behavior. Hobo spiders are docile and will typically run away when disturbed.
This matters because many pest control companies still market hobo spiders as dangerous. They are a nuisance. They belong outside your home. But they are not a medical threat.
Wolf spiders are large, fast, ground-hunting spiders that do not build webs. Several species in Davis County reach one and a half to two inches across. They hunt by sight and ambush, which is why you see them running across floors. Their size startles people, but wolf spiders are not medically significant. They move indoors in fall seeking warmth. Their eyes reflect flashlight beams at night, which can help with identification.
Yellow sac spiders are small, pale spiders that hunt at night and build tiny silk retreats where walls meet ceilings. USU Extension notes they are probably responsible for more spider bites in Utah than any other species. Bites are painful but produce only localized redness and minor swelling, similar to a mosquito bite. They move indoors in fall.
The woodlouse hunter has a dark reddish-orange head, large forward-pointing fangs, and a cream-colored abdomen. It is the spider most commonly mistaken for brown recluse in Utah. It hunts pillbugs and is not dangerous to people. If you think you found a brown recluse, it is almost certainly a woodlouse hunter.
USU Extension is clear: brown recluse spiders do not occur in Utah. Their native range covers the southern and midwestern United States. No verified brown recluse specimens exist from Davis County or anywhere in northern Utah. The spiders most often misidentified as brown recluse are woodlouse hunters, cellar spiders, and hobo spiders. If you are concerned about a spider you found, we can help identify it.
Homeowners often wonder why they still see spiders after a barrier spray kills ants, earwigs, and beetles quickly. The reason is biology. Spiders are arachnids, not insects, and they interact with treated surfaces differently.
Spiders walk on leg tips. Their bodies are elevated above the surface. Ants and beetles drag their abdomens across treated ground, picking up product along their entire body. A spider’s abdomen makes almost no contact with the surface it walks on.
Spiders do not groom their legs. Insects constantly clean their legs and antennae with their mouthparts. This means they ingest residual insecticide from grooming. Spiders do not do this. Their mouthparts never touch walking surfaces.
Spiders are naturally resistant to some insecticides. Research suggests that because spider venoms target the same nerve pathways that many insecticides use, spiders have evolved a degree of tolerance to those chemicals.
This is why a professional barrier spray works primarily by removing the food supply. The treatment kills crawling insects very effectively. As ants, earwigs, beetles, and crickets around the foundation die off, spiders lose the prey that attracted them to your home in the first place. Without food, they either leave, stop reproducing, or weaken and die. The direct contact kills matter too. But the food supply collapse is the mechanism that produces lasting results.
Spiders go where the food is. They settle near your home because your home attracts the insects they eat. Understanding what draws them helps explain why some homes have worse spider problems than others.
Window wells. The single most consistent spider habitat along the Wasatch Front. Window wells collect leaf debris, hold moisture, and create a dark sheltered space that attracts both spiders and the insects they feed on. Black widows and hobo spiders both nest in window wells regularly.
Exterior lighting. Standard white LED and fluorescent lights attract moths, beetles, and flying insects at night. Those insects attract web-building spiders. Switching to warm amber or yellow bulbs reduces insect attraction significantly.
Landscaping against the foundation. Rock beds, bark mulch, and shrubs planted tight against the house provide ground-level cover where hobo spiders and wolf spiders establish. A gap of at least 12 to 18 inches between vegetation and the foundation reduces harborage.
Stacked firewood near the house. Black widows are commonly found in firewood stacks. Moving wood at least 20 feet from the house and elevating it off the ground reduces encounters.
Foundation gaps and garage doors. Spiders enter through surprisingly small openings. Cracks around utility penetrations, gaps under garage doors, and torn window screens all provide access.
Spider activity follows a predictable cycle in northern Utah. Knowing when to expect increased pressure helps you time treatments for maximum effectiveness.
Spring (March through May). Hobo spider egg sacs from the previous fall begin hatching. Juvenile spiders disperse and start building webs. This is the best time for the first barrier treatment of the season.
Summer (June through August). Spider populations peak as juveniles grow and prey insect activity is highest. Wolf spiders and hobo spiders are active around foundations. Black widows are most visible in their webs during warm months.
Fall (September through November). The busiest season for indoor spider encounters. Male hobo spiders leave their webs and wander indoors looking for mates. Wolf spiders seek warmth. Yellow sac spiders move inside as temperatures drop. Boxelder bugs and other fall-invading insects draw spiders toward homes. The late fall barrier treatment specifically targets this migration window.
Spiders that enter your home in fall typically stay through winter. Most spiders seen indoors during winter were already inside before the cold arrived.
We spray a residual insecticide on the exterior surfaces that spiders and insects use to approach and enter your home. The treatment targets specific high-traffic areas, not your entire yard.
Where we spray. The foundation wall from ground level up, lower window frames, window well interiors, door frames, utility penetrations, and the interior perimeter of attached garages. These are the routes spiders take to get inside.
How it works. The spray dries to a residual film on the treated surface. Spiders and insects that cross the barrier are exposed to the active ingredient on contact. Each application lasts up to 45 days under normal conditions. Heavy rain, irrigation overspray, and direct sun can shorten the effective life of the treatment.
What you should expect. Within the first week, you will see fewer spiders and insects around treated areas. Some spiders may still appear near the barrier as they encounter it. That is normal and means the treatment is working. Over the following weeks, spider activity around the foundation should drop noticeably as both direct contact and prey insect reduction take effect.
De-webbing before treatment. Removing existing webs before or during application forces spiders to rebuild in treated areas and removes egg sacs. Egg sacs are resistant to insecticide sprays. Physical removal is the most effective way to eliminate them.
Spider control is available as a single application or as part of the four-treatment Exterior Spider Barrier Program.
A single treatment lasts up to 45 days. It is the right option if you have an immediate spider problem and want to knock it down quickly. It also works well for a specific event like the fall hobo spider mating season or as a trial before committing to the full program. A single treatment will not carry through the entire active season.
The Exterior Spider Barrier Program includes four treatments spaced from early spring through late fall. It maintains consistent barrier coverage across the full season when spiders and insects are active. The program handles the spring hatch, summer peak, and fall migration in sequence. This is what we recommend for homes with persistent spider pressure or anyone who wants year-round prevention.
The barrier spray is the most effective treatment. These additional steps reduce spider pressure between applications.
Install window well covers. This eliminates the most common spider habitat around Davis County homes. Covers keep debris, moisture, and insects out of the well.
Switch exterior lights to warm amber bulbs. Standard white LEDs attract insects at night, which attract spiders. Warm amber or yellow sodium vapor bulbs draw far fewer insects.
Seal gaps around your foundation. Caulk cracks around utility penetrations. Install door sweeps under garage doors. Repair or replace torn window screens.
Move firewood away from the house. Stack wood at least 20 feet from the foundation and elevate it off the ground. This removes black widow habitat from your home’s perimeter.
Trim vegetation back from the foundation. Maintain a 12 to 18 inch gap between shrubs, groundcover, and your foundation wall. This removes ground-level cover where hobo spiders and wolf spiders establish.
Current science says no. USU Extension states there is no significant evidence that hobo spider bites cause necrotic wounds. The CDC removed hobo spiders from its venomous spider list. They are a nuisance, not a medical threat. Black widows are the only dangerous spider in Davis County.
No. USU Extension confirms that brown recluse spiders do not occur in Utah. The spiders most often mistaken for brown recluse in Davis County are woodlouse hunters and cellar spiders, both of which are harmless.
Once the application has dried completely, treated surfaces are safe for contact. Drying time is usually a few hours depending on weather. We recommend keeping pets and children away from treated areas until the spray has dried.
Spiders resist residual sprays better than insects because they walk on leg tips and do not groom their legs. The barrier works by both direct contact and by killing the prey insects that attract spiders to your home. Spider populations decline over the following weeks as the food supply drops. Consistent seasonal treatments produce better results than a single application.
Each application lasts up to 45 days under normal conditions. Heavy rain, sprinkler overspray, and direct sun exposure can shorten the effective life. The four-treatment program maintains coverage through the full active season.
The first treatment of the season is most effective in mid-May to early June when juvenile spiders are dispersing. For fall spider pressure specifically, a treatment in September targets the hobo spider mating migration. The full program covers both windows.
We serve Davis County, Utah, including Bountiful, Layton, Kaysville, Farmington, Centerville, Clearfield, Syracuse, Fruit Heights, Woods Cross, West Bountiful, and North Salt Lake.
If spiders are showing up around your foundation, in window wells, or inside your home, contact us. We will evaluate your situation and recommend the right treatment.
Phone: 801-451-2220 Text: 801-893-8836