Treatment to eradicate Hobo spiders
The extension agent at the Montgomery site in NW Portland identified my spiders as Hobos 3-4 years ago, and explained how they nest against sides of buildings where other materials are stored (a condition that I have). Since then, their August mating routes have brought them into my house at an annual rate that has increased substantially, and I want to eradicate them / their nests so I can relax in my home. QUESTION: IS IT POSSIBLE, AND TO WHOM WOULD ONE GO FOR AN EFFECTIVE RESULT? I LIVE IN CONCORDIA / NE PORTLAND AND I HAVE TWO INDOOR / OUTDOOR CATS. Jan Coleman
Multnomah County Oregon
Hobo spiders (Eratigena agrestis) have been in the northwest for a number of years, with the first official documentation in Seattle, WA. There, these spiders are being displaced by a close relative, the giant house spider, Eratigena atrica. Unfortunately, the widely held belief that a bite from the hobo spider causes a necrotizing wound is a gross exaggeration of facts.
Facts include these: Spiders seldom bite people; if they do, it’s a defensive move. Then, too, a spider bite cannot be diagnosed by its appearance; instead, the spider must be caught in the act.
For more facts, please see “hobo Spider; Eratigena agrestis” - http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1769&context=extension_curall.
Management for hobo spiders includes (1) removing suitable habits; (2) sealing and caulking potential entry places; and (3) using sticky traps indoors immediately adjacent to exterior doorways.
Pesticides are of limited value. Most must be sprayed directly onto the spider to be effective. (For your safety, select a product with a label that states it is suitable for use indoors.) Simpler, and far less toxic is a sharp whack with a fly swatter or rolled up newspaper.
You might also consider interviewing several pest control companies to obtain their suggestions. See “Selecting a Pest Control Company” - http://npic.orst.edu/pest/selectpco.html.
Unfortunately, it is impossible to eradicate hobo spiders. Other spiders will move in as soon as they recognize an attractive, and available, living space.