By Vincent Lazaneo.
You may dislike spiders, but before you kill any, consider where they are located. In a garden, their webs may be a nuisance, but for the most part spiders in outdoor areas are beneficial because they help control many pests. Spiders commonly seen out in the open during the day are not likely to bite people or pets and their activity in the garden should be encouraged. Spiders are a part of nature and doing a few simple things can keep them out of your home.
When you see a spider in your home, you may wonder how it got there. Spiders, especially small ones, can accidentally be brought into a home hidden on firewood, potted plants, cut flowers and foliage, storage boxes, and other items. Spiders may also enter homes through cracks in walls, gaps around doors and room air conditioners, and open windows not covered with a tight screen. Check the exterior of your home and seal any openings where spiders and insects could enter. Also, carefully check outdoor items before you bring them inside.
Take steps to discourage spiders from living close to your home. Cutting back heavy vegetation or removing plants growing next to your home will help prevent spiders from taking up residence in or near them and then moving indoors. Remove fallen leaves, trash, and stored materials next to the foundation to deprive spiders of a place to hide. Wear gloves to avoid bites from secretive spiders, like the black widow. Use a hose, broom, or vacuum to periodically remove any webs and spiders from the outside of buildings.
Pesticides should not be used to control spiders outdoors. They usually kill more beneficial insects than spiders and will not provide long-term control. Within days or even hours, spiders can walk across a treated surface without being affected. Pesticides should not be sprayed on exterior walls or pavement next to a building; the toxic residue will harm fish and other aquatic life in streams and lakes when rain or irrigation washes the pesticides into storm drains.
If you find a spider indoors, there are several ways to get rid of it. Indoor aerosol products labeled for spiders are effective if you can spray the pesticide directly on the spider, but it may not die immediately. Instead of using a toxic spray, it’s just as easy to crush a spider with a fly swatter, rolled up magazine, or shoe. Also, spiders have soft bodies and usually do not survive removal with a vacuum.
If you don’t want to kill a spider, it can be removed from an indoor area by placing a jar over it. Slip a stiff piece of paper under the jar to seal the opening when the jar is lifted. The trapped spider can then be released outdoors where it belongs.
For more general information about spiders, or to learn more about specific spiders and their management, visit the UC Statewide Integrated Pest Management Program website.
All images courtesy of Jack Kelly Clark, University of California Statewide IPM Program.
Vincent Lazaneo is UC Urban Horticulture Advisor Emeritus. He has a master’s degree in horticulture and a teaching credential in vocational agriculture from UC Davis. In 1983, Vince began the Master Gardener program in San Diego. Vince frequently contributes, or has contributed to, the San Diego Union-Tribune, Mira Mesa Living, and other publications. He enjoys growing specialty plants in his home garden, reading, hiking, and fishing.