Most spiders are not harmful to humans and actually help to control other insects by eating them. The experts often recommend that spiders be captured and set free instead of being caught or smashed and killed.
While that may be the best thing to do, it is not always practical for some people -- especially the many who are afraid of spiders and don't want them anywhere around!
Keep Spiders Out
Spiders tend to spin their webs in quiet, secluded areas. To discourage these nests and around your home:
- Keep firewood and logs away from the home. Clean up leaves and other organic debris from around the yard. Trim back any trees and shrubs that contact the home.
- Caulk or otherwise seal cracks and gaps in the home's structure, especially around foundations windows and doors.
- Ensure doors and windows fit tightly in their frames, have no tears or holes in screening, and have sweeps installed at the bottom edge of doors.
- Reduce the insects that attract the spiders by replacing standard mercury vapor lights with high-pressure sodium vapor or halogen lights. Although it is common to place lights on exterior walls near doors, it is better to place the light farther away, using pole lights when possible, with the light shining toward the door for safety.
- Reduce or eliminate piles of papers, boxes, bags, and other clutter to reduce potential harborage areas.
Non-Chemical Control of Spiders
- Remove spiders that are nesting on the exterior of the home by spraying water from a high-pressure hose, sucking them into an industrial vacuum, or brushing them off with a long-handled broom. Be sure to remove egg sacs as well.
- Indoors, spiders can be discouraged from web-building and making spider nests through frequent vacuuming and sweeping of corners, closets, basements and other out-of-the-way places.
- When vacuuming, sweeping or otherwise removing webs, be sure that all egg sacs are captured and spider nests removed to prevent a new generation from being born.
- A fly swatter or rolled-up newspaper can also be used to kill individual spiders. When doing so, it can be prudent to find and destroy its web to ensure against egg hatching as well.
- Use Integrated Pest Management (IPM), including prevention, sanitation, and exclusion, to reduce insects. This will help reduce spiders both directly and indirectly—by reducing the "food" on which they prey.
- Check your boxes, plants, and firewood before bringing it into the home to ensure that spiders are not hitching a ride.
Chemical Control of Spiders
- A residual pesticide sprayed under siding and into cracks and crevices where spiders harbor can temporarily keep spiders from spinning their webs on your home. Use only pesticides labeled for spiders, the spider to be controlled, and the area where the application is intended. Reapply as specified on the label.
- Pyrethrin or pyrethroid space sprays can kill spiders that are directly contacted, but they will have little residual effect, so the application should be made to contact as many spiders and webs as possible. The space spray will need to be repeated when spider eggs hatch, generally in about 4 weeks.
- A light application of an aerosol or liquid insecticide that is labeled for spiders can be applied into cracks and gaps where spiders can provide some control.
- Pesticide dust can provide control in secluded areas, such as voids where spiders harbor. The dust that contacts webs will stick and be eaten by spiders as they digest the web's silk to reproduce more.
Some species can be dangerous and require immediate elimination, so it is important to identify the spider before attempting to control it.
When a dangerous spider is identified, such as the black widow, brown recluse, or hobo spider, it is best to contact a pest management professional who has the knowledge, tools, and equipment to safely deal with the problem.