Pests in Gardens and Landscapes: Quick Tips

Spiders

Published   3/14

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Adult black widow spider showing the red hourglass mark on underside of abdomen.

Adult black widow spider showing the red hourglass mark on underside of abdomen.

Sac spiders occur indoors and out and hide in silk tubes in corners or under bark.

Sac spiders occur indoors and out and hide in silk tubes in corners or under bark.

Cellar spiders have long skinny legs and often hang upside down.

Cellar spiders have long skinny legs and often hang upside down.

Spiders are mostly beneficial because they feed on pest insects. However, many people think that all spiders are dangerous and aggressive. In California, the main spider capable of causing serious injury is the black widow, which generally remains outdoors and out of sight. Spiders seen out in the open during the day are unlikely to bite people. Focus pest management efforts on removing webs and hiding places. Pesticides are not generally recommended.

What to know about spiders:

  • The jaws of most spiders are too small to bite humans.
  • Adult female black widows are the main spiders capable of seriously injuring people in California. They are shiny black with a red hourglass marking on the underside and are commonly found outdoors, in sheltered, dry, undisturbed areas such as wood piles and garages.
  • Anyone bitten by a black widow spider should remain calm and seek medical advice.
  • The brown recluse spider and the hobo spider do not live in California.
  • Some other spiders bite when trapped in clothing or bedding, but the effect is usually no more severe than itching or the reaction to a bee sting.

To prevent spiders from entering your house, take these steps:

  • Seal home foundation cracks and other access holes.
  • Inspect window and door screens for good seals to keep out spiders and the insects they prey on.
  • Keep areas around home foundations free of clutter.

Manage spiders using these tips:

  • Indoors, regular housecleaning provides adequate spider  control.
  • Vacuum up the spider and its web.
  • Alternatively, squash spiders or capture them in a jar and release them outside.
  • Prevent clutter buildup that can provide spider hiding places both indoors and out.
  • Remove spider webs from the exterior of the house with a broom or high pressure hose.

Spiders and biological control:

When removing spiders, don’t overlook the fact that spiders eat a large number and variety of nuisance and pest insects. Spiders also have natural enemies — wasps, other spiders, birds, reptiles, and others — that sometimes keep them from becoming too numerous.

Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.


Statewide IPM Program, Agriculture and Natural Resources, University of California
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