At this time of year, the WSU Extension Clark County Master Gardener Answer Clinic gets an increase in calls about spiders in the home. Though they are indeed creepy-crawly, they aren’t the bad guys some think they are. Here is some information from a spider specialist at Washington State University:
Most of our native spider species start the year off as overwintering eggs. Throughout the spring and early summer, they tend to exist as immature spiders that go about their lives as predators. Armed with silk, fangs and a multitude of hunting strategies, they prey on insects and other spiders. In this regard they are considered beneficial organisms, as they prey on insects that are garden pests and insects that “bug” us.
By the end of summer, mature male spiders tend to go for “walkabouts” in search of female spiders of their own kind. Some male spiders tend to stumble indoors in their search for females where they may be treated as unwelcome guests by homeowners.
In early autumn as night time temperatures start dropping towards freezing, mated female spiders start on walkabouts of their own. They are looking for sheltered places to lay their eggs and provide the best protection for those eggs to overwinter. Thus some female spiders wander indoors in response to warmth and shelter. Again, they may be treated as unwelcome quests by homeowners despite all the predation they have done outdoors for us.
Please note, there are a few species of spiders, like house spiders and cellar spiders, that will make themselves right at home in our homes! These spiders are still predators of insects and other spiders that intrude into our homes. Yeah! Nevertheless, while spiders outdoors are considered beneficial by most people, spiders indoors are in the wrong place, wrong time and most people do not appreciate them.
The very best way to manage spiders is to exclude them from the home in the first place. Find any cracks and crevices in the foundation of the home and caulk or seal them up. Pay attention to the cracks, crevices and corners in the frames around windows and doors. Check the bottom of doors for spaces that spiders can just walk right through. Consider installing door sweeps. Repair any holes in your screens and be sure to check attic vents. You can apply insecticides around the foundation of the house, but this is only a temporary solution. Those crack, crevices, tears, and openings will still be there for spiders to walk through next season.
One other important fact to note: Brown recluse spiders are NOT found in the Pacific Northwest. The only spider known to be venomous to humans in Washington (but only on the eastern side of the state) is the western black widow spider and these spider bites are only in self-defense and rarely encountered. Reports of spider bites from other PNW spider species have not been confirmed as venomous despite research in this area.
There is concern that spider bites can become infected with harmful bacteria that causes health concerns, so always keep your eyes on a suspected spider bite and make sure it does not become infected. If the bite becomes red, swollen, increasingly tender to the touch, see your primary physician.
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Michael Bush, has a doctorate in entomology and pest management and works with WSU Extension- Yakima County. Additional input from Susan Cox and a picture from Laura Heldreth, WSU Extension Clark County Master Gardeners.
