Control spiders by changing environment

Q. We have a lot of spiders around the outside our house, and I’m concerned that they might be dangerous. I can’t get near spiders, so I can’t bring in a sample. What can I do to get rid of them?

Jane from Youngstown

A. Jane, a lot of people are afraid of spiders, so I understand you not wanting to get near them. But without a sample, we cannot tell you exactly what type of spiders you have or if any of them are dangerous.

That said, it’s unlikely that of any you see are harmful. Of the 500 to 600 species of spiders found in Ohio, only four are potentially harmful or dangerous to people: the brown recluse and black widow spiders.

Brown recluse spiders are usually found in or around buildings. They are about 1/3-inch long, chocolate brown with a fiddle-shaped mark on top and have long legs. They probably won’t survive a winter outside in the Mahoning Valley and are not on published distribution maps as being in our area. They are in Southwest Ohio, though. There are two species in Ohio: the brown recluse (Loxosceles recluse) and the Mediterranean recluse (Loxosceles rufescens). As their names suggest, they prefer hidden spaces and mostly go unseen.

The two species of black widow in Ohio are the black widow (Latrodectus mactans) and the northern widow (Latrodectus variolus). They are normally shiny black. Females have the signature red markings on top; males have white marks underneath. They are commonly found in abandoned buildings, sheds and old barns.

All four of these spiders are more likely to be found in southern and western Ohio than in the Mahoning Valley.

Aside from using an insecticide, a good way to control spiders is to change the environment where they’re found. All spiders are predators, so cleaning up an area that may have insects – the spiders’ prey – will encourage them to move to another location. Use a broom or vacuum to remove any spider webs you find. Also, reduce the use of outside lighting to minimize attracting insects, and thus, spiders to your house.

As a last resort, you can lightly use a broad-spectrum insecticide around the exterior of your house. If you choose to use an insecticide, be sure to read and follow all instructions on the label.

Spiders, like most other invertebrates, live out their lives largely beyond our notice, performing valuable functions in the environment.

For more information, visit go.osu.edu/recluse and go.osu.edu/Ohiospiders.

Today’s answer was provided by David Sprague, OSU Extension master gardener volunteer. Call the office hot line at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.