Tips & Tricks: How to Control Spiders


June 1, 2013

Headshot: Marie KnoxControl Solutions Inc.
By Marie Knox, PCO Technical Services Manager

Spiders are beneficial arthropods because they prey on and eat insects (among other pests); however, this fact does little to convince homeowners they should share their residence with these eight-legged, uninvited houseguests. While knowing a pest management professional (PMP) is on the job might help some homeowners to sleep better at night, it’s vital you communicate with your customer and get their cooperation during and after their “spider crisis” has been resolved.

An integrated pest management (IPM) approach begins with identifying the pest and inspecting the surroundings to determine conducive conditions, as well as potential harborage areas and food sources. A preferred habitat for spiders is an undisturbed environment with a food source (insects), which is where homeowners’ habits can make or break spider control. Communicate upfront with your customer, and let them know what steps they can take to make their homes less spider friendly. Clutter inside and outside of a structure creates favorable harborages and makes treatment difficult. Removing clutter inside the home (closets, playrooms, cabinets, bookshelves, etc.) and outside (moving wood plies and debris away from the structure, trimming landscaping, etc.) helps reduce the number of places spiders can live and hide. Regularly disturbing spider habitats by moving furniture when cleaning, rotating items regularly in closets and on shelves, and reducing the accumulation of stuff in the garage also helps making a structure less desirable for spiders.

Spiders are feeding on insects, so inspecting a structure inside and out for insect pests and treating to reduce insect populations is an effective step to reduce the spider’s food source, and, therefore, the spider population at a structure.

Headshot: Doug VanGundyCentral Life Sciences
By Doug VanGundy, Senior Director, Research and Development

As warmer weather approaches, property owners might start to notice an increase of spider activity in and around their residence. To control spiders, pest management professionals (PMPs) must use an integrated approach, while educating customers on proper techniques to prevent future infestations. Tips to help you and your customers identify and control a spider infestation are:

  • Conduct a complete inspection indoors and out to identify the source of the infestation, points of entry and spider species.
  • Remove webs, egg sacs and areas for harborage.
  • Dispose of all clutter in storage areas — such as garages, sheds and attics — to eliminate web-building sites.
  • Repair and caulk any cracks or holes in the exterior of the building.
  • Treat spiders with a residual insecticide that can stay on top of porous surfaces.
  • A perimeter application of a broad-spectrum insecticide can help eliminate insects that act as spiders’ food source.

Kyle_Jordan_0613BASF Pest Control Solutions
By Dr. Kyle Jordan, Market Development Specialist

Controlling spiders and other pests is easiest when following a step-by-step process:

  1. Inspect to gather information.
  2. Prescribe a treatment strategy.
  3. Communicate with the client.
  4. Treat using effective techniques and materials.
  5. Follow up to assess results.

Spider control might divide the first two steps of this process, depending on which of the two primary groups of spiders — web spinning or hunting — is present. Each of the two groups requires a different control strategy.

The strategy for web-spinning spiders is relatively simple: Apply product directly to the spider as it rests on the web or in or on surrounding harborages using a pinstream or another direct application. Additionally, removing the web plays an important part in control and provides a benchmark for subsequent inspections.

Control of hunting spiders can be more complex. Typical treatment involves a thorough pesticide application to mulch and vegetation, as well as any gaps on the structure, especially beneath siding — always penetrating deep into protected areas where spiders hunt or hide.

Headshot: Elray RoperSyngenta Professional Pest Management
By Dr. ElRay Roper, Senior Technical Representative

Spiders can scare homeowners. Some can be poisonous to humans, but oftentimes spiders and their webs are more of an aesthetic nuisance. To control spiders, PMPs should identify the spider species and then implement chemical and physical controls to remove spiders from their customers’ property.

  • Inspection and identification. A thorough inspection of the inside and outside of a building is critical to determine the types of spiders, their entry points and the sources of infestation.
  • Chemical controls. Insecticides are effective when applied to areas of spider harborage and activity as a spot or crack-and-crevice treatment.
  • Physical controls. Sealing holes and cracks on the outside of a building is the best way to prevent spiders from coming inside. However, long-term success of spider control is contingent on removing any harborage areas. This can include cleaning areas of webs and egg sacs by vacuuming, flushing and other general sanitation efforts. Additionally, changing the way the building facade is lit can help deter spiders from setting up webs around doors and windows. Indirect lighting pointed toward the building is best.

Headshot: Cisse SpraginsRockwell Labs Ltd
By Founder and CEO Dr. Cisse Spragins

Spider control varies depending on the location and species of spiders. For most outdoor dwelling spiders that tend to build webs around and on structures, the mainstay of treatment is spraying the underside of the eaves of the structure. Indoors, glueboards can be effective for capturing occasional spiders. Glueboards can be deployed in smush-resistant stations to keep out dust and keep them from getting stuck to the wrong surfaces. For spiders such as brown recluse or yellow sac spiders, which dwell indoors and can reach large numbers, amorphous silica dust, in addition to glueboards, can be applied in attics, cracks and crevices, and under furniture seat cushions.

Clutter reduction in a structure also is important to reduce harborage sites. Boathouses, boat docks and other structures near water are notorious areas for spiders to build webs. Pyrethroids can’t be used over or near water. An ideal solution to prevent web construction is to mix amorphous silica gel with water and spray the undersides of docks, rafters, eaves, etc. The water will evaporate and leave a fine film of the dust, which, although visible on dark surfaces, is effective. This treatment won’t provide any risk to aquatic life or leave oily residue on the water.

Headshot: Joe BarileBayer CropScience LP, Environmental Science Division
By Joe Barile, Technical Services Support

Probably no pest group creates more anxiety among the public than spiders. PMPs are asked routinely to provide service for these shy, unassuming creatures. Fear of health threats from spiders — usually based on amplified urban myths of aggressive biting dangerous venoms and flesh-eating wounds — are exaggerated many times. Spider bites contribute to a miniscule number of human and animal medical interventions.

Hundreds of spider species are found commonly throughout the United States and Canada. Of all these species, only a few generate legitimate concern from a public hazard perspective. Almost all real exposures are accidental, in which people unknowingly threaten the animal in its environment.

Managing spider activity in and around structures must begin with understanding the predator/prey relationship. Spiders are predators of living animals, mostly insects and other like-sized arthropods. The continued presence of spiders on, around or inside structures is a clear indication that a population of suitable prey is readily available.

Headshot: Dina RichmanFMC Professional Solutions
By Dr. Dina Richman, Development Manager 

There are more than 2,000 species of spiders commonly found in the United States, but only a few indigenous species cause harm, including the black widow and brown recluse. Despite their usually harmless nature, the stigma and fright caused by spiders mean control is an important service provided by the pest management industry. 

To offer customers an integrated approach to spider control, consider:

  • What species is involved? If the target pest is one that inflicts poisonous bites, ensure technicians are protected suitably from contact with the adult spiders. Any control products should be nonrepellent to avoid exacerbating the problem by causing dispersal of infestations.
  • What’s the true source of the problem? Often, spider webs in the occupied areas of a home or office are merely the tip of the infestation iceberg. Make sure basements, crawlspaces and unused storage areas are inspected to evaluate the exact extent of the infestation.
  • Why are spiders present? Spiders are predators feeding on other arthropods. Often, their presence is an indication of other pest problems. Eliminating conditions conducive to these pests will lead to more sustainable control of spiders.
  • Can physical control be used to achieve effective results? Sometimes feather dusters or vacuum cleaners are sound first steps of control. Although the use of appropriately registered insecticides is useful to extend the effective control period, they always should be combined with nonchemical approaches to support an IPM approach.

Headshots: Stoy HedgesTerminix
By Stoy Hedges, BCE

All spiders have venom glands, but the venom of most spiders isn’t dangerous to people. Two exceptions in the United States are the black widow (three species) and brown recluse spiders. Spider bites exceedingly are rare and typically occur when the spider becomes trapped against one’s skin while the spider is hiding in a shoe, glove or other clothing. Bites also might occur when a person sticks his fingers in a black widow’s web while turning over items under which the spider is hiding.

Physicians often diagnose many skin lesions or open wounds as “spider bites” even though the patient hasn’t reported feeling or seeing a spider bite on their skin. Several conditions can cause skin bumps, red areas and open wounds, the most important of which are bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA).

As pest professionals, it’s not our job to try to be a doctor and say, “That looks like it could be a spider bite.” Rather, if customers say they think they might
have been bitten by a spider, our job is to inspect and place monitoring traps
to see whether any brown recluse spiders are present and the extent, if any,
of the infestation. 

Headshot: Ron SchwalbNisus Corp.
By Ron Schwalb, A.C.E., National Technical Manager

Spiders primarily are beneficial, so their activities should be encouraged in the garden and areas away from the house. Prevention should begin before spider populations become too large or before certain venomous spiders invade the structure. The best approach to controlling spiders is to start an integrated program early that includes inspection, prevention, exclusion and sanitation.

Inspection. Spider infestations might be in the form of web makers that create webs on the inside and outside of structures and ground predators that might crawl into structures looking for insect prey. When checking exteriors, keep an eye out for potential harborage and food sources, as well as likely entry points. Spiders overwinter well, so a thorough interior inspection is essential, especially in less-visible areas of crawlspaces, storage rooms and garages. Property owners can give you plenty of information about any sightings or concerns.

Prevention, exclusion and sanitation. Spiders gain access to structures through cracks and other openings. They can be introduced on items such as firewood, plants and stored boxes. Seal cracks and crevices in the foundation. Caulk around windows and doors. Remove all debris next to the foundation, and trim shrubs and trees away from the structure to prevent protective harborage. Make sure all window screens are intact. If not, suggest repair. Inspect firewood and other material brought into the interior of the structure. 

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