Many people are deathly afraid of spiders, which is a shame. Not only are most spiders harmless to people, but the vast majority of them are helpful.
Spiders are predators that feed on insects, and most of the time are quite beneficial to our environment because they consume lots of mosquitoes and other pest insects, many of which are known disease vectors.
Except for webbing and egg sacs, which really are more of a nuisance than anything else, spiders will not damage a house or its contents in any way. Neither do they generally bite humans except in self-defense, such as when we accidentally sit on them.
Most of the time, spiders outside a home really should be left alone. They do more good than harm. It’s mainly when they get inside homes and buildings that spiders can create a problem requiring the services of a pest control professional.
Funnel-Web Weaving Spiders
There are many species of spiders in the Pacific Northwest, most of which are harmless and beneficial. Only three spider species account for the lion’s share of calls to exterminators in Portland and Vancouver. All three species belong to genus Tegenarra and collectively are known as the funnel-web weaving spiders. They are the barn funnel weaver (Tegenaria domestica); the hobo spider (Tegenaria agrestis), shown on the top of this page; and the giant house spider (Tegenaria gigantea).
The Hobo Spider
These funnel-web weaving spiders used to be considered entirely beneficial and harmless to humans. However, we now have good reason to believe that at least one of them, the hobo spider, has been going around biting humans, resulting in annoying skin lesions and, occasionally, serious illness. For years, these bites were blamed on the brown recluse spider, but brown recluse spiders are exceedingly rare in the Pacific Northwest. Once in a while one will hitchhike a ride in a truck or a boxcar, but they’re not native to our area and are very rarely encountered.
Hobo spiders, on the other hand, are common here; and it now appears that the bites we used to blame on the brown recluse are actually be inflicted by hobo spiders. Most bites occur when the spider is pressed against a person’s skin and is unable to escape.
When hobo spiders are numerous in and around a home, you may want to consider professional spider control. Inside homes, hobo spiders are usually found in secluded areas that we don’t clean very often, lurking there among the dust bunnies. They’re commonly found under and behind furniture; in furnace and boiler rooms; behind washers, dryers, and other appliances; in basements, crawl spaces, attics, storage rooms, and unused cabinets; and in cracks behind the trim of windows and doors.
Outdoors, hobo spiders and their webs are often found in firewood piles, in piles of junk and debris, under tarps and closed patio umbrellas, under porches and decks, and other similar, secluded spaces.
Western Black Widow Spiders
The Western black widow spider is another dangerous spider found in the Pacific Northwest, but it’s of limited concern to those of us in Portland and Vancouver. They’re more common in the Southwestern parts of Oregon, and only occasionally make their way up North. They’re found most often in corners of dark places like garages, basements, crawl spaces, and unused sheds.
The Western black widow is probably the most dangerous spider in the Pacific Northwest. Their venom contains a neurotoxin than causes symptoms including abdominal muscle cramps, nausea, tremors, labored breathing, and possibly death. If you think you’ve been bitten by a black widow, you should seek medical attention immediately.
That being said, fewer than 1 percent of black widow bites prove fatal, and we don’t get them very often in this part of the state, anyway. We do get a lot of spiders that look a bit like the Western black widow. One of these, conveniently enough, is actually called the “false black widow spider.” Its body size and shape look a lot like the Western black widow, but it lacks the red marking.
Long story short, you’re not very likely to come across a Western black widow spider in our neck of the woods; but because we do encounter them once in a while, we thought we should at least mention them.
Spiders can be difficult to control. They don’t readily take baits; and convention, residual sprays are not very effective on spiders. Spiders are able to walk tippy toed on surfaces that was sprayed with residual insecticides without actually taking in a toxic dose. Sprays are effective when you spray them directly on to the spider, but spiders are usually in hiding when the exterminator comes around.
Like all of our services, our approach to spider control seeks to maximize control while minimizing pesticide use. To this end, we have three spider control plans, and will recommend the one we believe to be most appropriate for a given situation.
- The Basic Plan. Out first spider control plan is called the Basic Plan, and is focused of preventing spiders outside the house from getting inside the house. This is an exterior-only service, including treating around the foundation, planting and flower bed areas, decks, doors, vents, and windows. The goal is to knock down the spiders that we can treat directly, but also treat the cracks, crevices, and other gaps that they would use to get into the house.
- The Basic Plan Plus. The next step up from the Basic Plan includes all the above, plus the crawl space. To treat the crawl space we use a tool called a “Thermo Fogger,” which generates a cloud or fog of insecticide that permeates up under the insulation. The insecticide we use is 3% pyrethrum (a natural product derived from chrysanthemum plants) and deodorized mineral spirits.
- The Complete Treatment includes all the above, plus a crack and crevice treatment in the interior using a small motorized duster tool. The dust is precisely injected into cracks and crevices, wall voids, around electrical fixtures, and so forth, not into the air.
In most cases, the Basic Plan is really all you need, or the Basic Plan Plus if your house is built over a crawl space. The Complete Treatment usually is only necessary if you already have spiders inside your home. Many customers start with the Complete Treatment, but then back off to occasional exterior-only treatments once the problem with spiders inside the house has been solved. That’s a perfectly sensible way to approach the problem.
Non-Chemical Spider Control Tips
With a bit of effort, there are several things that you can do yourself to reduce the number of spiders in and around your home. Depending on the severity of the spider problem and your own tolerance for spiders, following these steps may be all the spider control you need.
- Clean and tidy up the grounds. Spiders like to hide in and under things, so remove as many things for them to hide in and under as possible.
- Vacuum them Up. Vacuuming spiders and their webs is a perfectly good way to quickly reduce populations. Just be sure to seal the bag (or empty the canister in a bagless vac) into an intact plastic bag (one with no holes), seal it, and put it in the trash once you’re done.
- Use sticky traps in areas like attics and furnace rooms. Be careful not to put them where you, your children, your pets, or non-target animals will step on them.
- Move shrubs and plants farther from your home. Two or three feet should be enough. You should be able to walk between your house and the plants.
- Caulk and seal cracks and crevices around the outside of your home. Take a caulking gun to door and window frames, cracks in brickwork, and other potential entry points.