Boat docks, basements — have spiders no shame?


November 16, 2021

Judy Black

Judy Black, VP of quality assurance and technical services for Rollins Inc. and PMP Hall of Fame member (Class of 2019)

Question: Judy, many of my customers have lake homes with boat docks. The docks often are covered with spiders and webs. I know they aren’t public health threats like black widows or brown recluses, but I still need to do something about them. Is there something I can treat with, without risk of contaminating the water?

— Always Looking, Longing While Ecologically Trumped

Answer: I get this question a lot, ALL WET. From an integrated pest management (IPM) perspective, we want the customer to keep the lights turned off on the dock at night. But the whole point of having lights on the dock is safety and theft prevention, so that isn’t a realistic recommendation. You can check to see if they can light the dock from lights placed away from the dock, but even that is not always practical. Plus, it’s likely to just reduce the problem, not eliminate it.

Take a look at some of the products that are exempt under the U.S. Environmental Protection Agency’s (EPA’s) Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) 25(b) provision. The ones I recommend have spiders on the label, and specific language about treating docks and/or marine vessels.

You should get a pretty good contact kill with these types of products, but the residual may be less than what you are used to with conventional materials. This shouldn’t be an issue if you set the customer’s expectation and adjust your frequency to what is needed.

Question: Judy, I’m finding spider webbing in my customer’s basement, but no spiders. They look like matted up webbing — not like an orb from Charlotte’s Web. I’ve sprayed cracks and crevices, and even made spot applications on surfaces, but it doesn’t seem to be getting better. This customer is deathly afraid of spiders. Do you have any suggestions on what I can do?

— Spider Problem Ideally Done Efficiently Yesterday

Answer: It sounds like you are dealing with house spiders (Achaearanea tepidariorum), SPIDEY. I included the scientific name because this spider has a few different common names used around the country. I’m guessing that is what you are dealing with because of the webbing description. House spider webs usually are described as tangled, which seems like another way of saying “matted.” One house spider also can make a lot of webs. They are really random in their hunting technique. Build a web here and see if it catches anything; if not, move on. They keep doing that until they start catching prey. Given this behavior, it can be hard to find the active web.

I wish I could give you a solid pesticide recommendation, but I can’t. The most success I’ve had in these circumstances is using a vacuum and sealing up entry points to the basement. Just knocking down the webs when you are on the interior often is counterproductive because you get the web and maybe the egg sacs, but the adult gets away to build webs another day. With the vacuum, you are likely to get the adult, too.
I endorse knocking down webs on the exterior, but on the interior for house spiders, it’s not the best tactic. Exterior pesticide treatments can help reduce prey entry into the house. I will caution you, though, that this isn’t the end-all solution, because most spiders can live weeks without food.

If you can get your customer to become a “spring cleaning” advocate, that can really help. Just moving old boxes and such around and cleaning every year can disrupt house spiders. The customer is still going to need you because spring cleaning won’t eliminate the spiders, but it will help.

Email your questions about insect identification and pest management technologies to Your questions most likely will be printed and answered in one of Pest Management Professional’s upcoming columns.

About the Author

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BLACK is a PMP Hall of Fame member (Class of 2019) and VP of quality assurance and technical service for Rollins Inc. She may be reached at

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