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Spider Control
Spiders are predators, which means a lot of them is a signal about something else. Treating the spiders without touching what they are eating buys you a few weeks. Here is the mechanism, and the reason barrier sprays underperform on this one pest specifically.
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The short version
A sudden increase in spiders almost always means the insect population they feed on increased, and exterior lighting is the most common reason. Residual barrier sprays also work poorly on spiders in particular, for a physical reason most product labels don’t explain: a spider walks on the tips of its legs and picks up very little treated surface. Change the light, clear the webs mechanically, and seal the gaps — in that order.
Actual cause
Usually the food supply
Most common lever
Exterior lighting
Why sprays underperform
Minimal body contact
Works best
Mechanical removal
Why there are suddenly a lot of them
Spiders are predators. A population that grew is telling you the insect supply grew, and there are usually only three reasons.
Most common
Exterior lighting
A bright white fixture near a door pulls flying insects in all night. The heaviest webbing is almost always within a few feet of a light, a lit window, or a door left open in the evening.
Second
Harbourage
Firewood against a wall, cardboard on a garage floor, ground cover running to the foundation, unused pots. Undisturbed cover to sit out the day in.
Seasonal
Autumn wandering
Ground hunters come indoors in autumn following prey and warmth. They’re passing through rather than nesting, which is why treatments aimed at residents underperform.
The exception
A species you can’t place
Almost every spider in a house is harmless and the medically significant ones are regional and uncommon. But identification is the one thing worth an inspection — and it should happen before anybody treats anything.
Why there are suddenly a lot of them
Spiders do not eat your house, your plants or your food. They eat insects. A population that has visibly grown is telling you the insect supply grew, and the single most common reason at a residential property is lighting.
A bright white exterior fixture near a door or a porch pulls in flying insects for the whole night, every night. The webs follow the food, which is why the heaviest webbing is almost always within a few feet of a light, a lit window, or a doorway people leave open in the evening. Deal with the light and the population falls on its own, because you have removed the reason it was worth living there.
The second most common reason is harbourage. Firewood stacked against a wall, cardboard stored on a garage floor, dense ground cover running right up to the foundation, and unused plant pots all provide the undisturbed cover spiders need to sit out the day.
Why spraying disappoints
This is worth understanding before you buy anything, because it explains a result that otherwise looks like a bad product or a bad technician.
A residual barrier spray works by leaving an insecticide film on a surface that an insect walks across and absorbs through contact. It works well against insects that drag their bodies over the treated surface. Spiders walk on the very tips of their legs and hold their bodies clear, so the contact area is a fraction of what the product was designed around. They can cross a treated band and pick up too little to matter.
A direct contact spray hits the spider you aimed at, and that works fine. What it does not do is prevent the next one, because the food that drew it is still there. Broad-spectrum spraying also kills the beneficial insects and the predators, which is the wrong half of the ecosystem to remove if your problem is that there are too many insects.
What actually works, in order
Change the exterior lighting. Warm-toned bulbs attract dramatically fewer flying insects than cool white ones. Motion-triggered fixtures remove the all-night draw entirely. Where you need light for security, moving the fixture away from the door and pointing it back at the door works better than lighting the doorway itself.
Remove webs mechanically and keep doing it. A brush or a vacuum on an extension pole, along the eaves, under the deck rail, around window frames and light fixtures. This is the most effective single thing you can do, it costs nothing, and it works because it removes the egg sacs along with the webs. It needs repeating; that is the trade.
Seal at ground level. Door sweeps, gaps around utility penetrations, torn window screens, the gap under a garage door. This is the same work that improves your heating bill.
Clear the harbourage. Firewood off the wall and up off the ground, cardboard out of the garage, ground cover pulled back from the foundation.
What actually works, in order
Ranked by effect. The first two cost almost nothing and do most of the work.
Change the exterior light
Warm-toned bulbs draw dramatically fewer flying insects than cool white. Motion-triggered removes the all-night draw entirely.
Move the fixture
Where you need light for security, mounting it away from the door and pointing back at the door beats lighting the doorway itself.
Clear webs mechanically
A brush or vacuum on a pole along eaves, deck rails, window frames and fixtures. This removes egg sacs as well as webs, which spraying does not.
Fit door sweeps
Plus gaps at utility penetrations, torn screens, and under the garage door. The same work that improves your heating bill.
Clear the harbourage
Firewood off the ground and away from the wall, cardboard out, ground cover pulled back from the foundation.
Doing it yourself against hiring it out
The point to hand it over
A bite followed by spreading discolouration, an expanding sore, or an area that keeps getting worse over days is a medical question, not a pest control one. See a doctor. Worth knowing before you do: skin infections are very commonly mistaken for spider bites, including by people who are certain they saw a spider, and the treatments are entirely different. Bring the spider if you have it; do not go looking for one.
A genuine recluse population inside a structure is regional, uncommon outside its range, and a different job from the perimeter work on this page. It needs an inspection that establishes whether you actually have one before anybody treats anything, because almost everyone who thinks they have one does not.
Anything requiring you to be in a crawl space or an attic you cannot stand up in. The spiders are not the hazard there.
Signs you hired the right person
Diagnosis
Asks what they’re eating
A species and a light fixture is a diagnosis. A treatment schedule is a sale.
Method
Removes webs mechanically
Brushing takes the egg sacs with it. Spraying doesn’t.
Advice
Names what to change
Lighting, harbourage, gaps at ground level. None of it appears on an invoice.
What to ask on the call
- What do you think is feeding the population here?
- Does the quote include mechanical web and egg sac removal, or only spraying?
- Which species have you identified, and from what?
- Is exterior lighting or harbourage part of what you’d recommend?
The first question does most of the work. A company that answers it with a species and a light fixture is diagnosing. A company that answers it by describing their treatment schedule is selling one.
Frequently asked
Why do barrier sprays not work well on spiders?
A spider walks on the tips of its legs and holds its body clear of the surface, so it picks up a fraction of the residue a crawling insect would. The product isn’t failing; the contact area is.
What attracts spiders into a house?
Insects. A bright exterior light near a door pulls in flying insects all night and the webs follow the food. Change the light and the population falls on its own.
Do I need pest control for spiders?
Usually not. Clearing webs, swapping to warm-toned or motion-triggered exterior lights and fitting door sweeps does more than a spray, and costs less.
How do I know if it’s a brown recluse?
Small, uniformly tan, smooth rather than hairy, thin legs, and retiring. If it’s large, hairy and sprinting across the floor, it isn’t one. Recluses are regional and far more often reported than found.
Indoors, in numbers, and you don’t know what they are?
Perimeter webs, eaves and a bright porch light are yours to fix, and the fix costs less than a visit. An established population inside the structure, or a species you can’t identify with confidence, is worth an inspection before anyone treats anything.
Call (877) 360-4657