Bayer CropScience LP, Environmental Science Division: Spiders


June 21, 2013

By Joe Barile, Technical Services Support

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

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

Management of 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. Additional tips for a spider management regimen include the following:

• Classify the spider at least by “prey acquisition”: active hunters, passive hunters or web builders.
• Identify and create a prey management plan by:

  • Looking in webs for discarded prey corpses; inspecting for occasional invaders; and interviewing occupants about other pest activity.
  • Inspecting for moisture conditions and site sanitation that support prey species; trim ornamental plantings from direct contact with the structure; and advise on debris removal (leaf litter, woodpiles, toys, lumber, etc.) in and around structures that create harborage for spiders and their prey.
  • Inspecting and advising clients on outdoor lighting so as not to attract night-flying insects (moths, beetles, midges and gnats).
  • Advising clients on potential entry into the structure around windows, doors and fixtures.

• Stay active:

  • Physically remove spiders and their webs with vacuums and/or brooms. Destroying and removing webbing puts physiological stress on resident spiders.
  • Seal entries into the building, including door/window frames and screen moisture weep-holes.
  • Ventilate closed spaces, as moisture reductions reduce prey populations, and moving air repels spiders.
  • Kill exposed spiders with suitably labeled contact insecticides.
  • Treat spider harborages with residual insecticides for longer-term control. Pyrethroids and pyrethroid/neonicotinoid combinations perform well.
  • Choose a formulation (liquids, aerosols and/or dusts) appropriate to the site conditions.
  • Always read and follow all label directions for product application.

In some cases, such as properties close to wetlands that continually produce flying insect prey, clients must be educated by PMPs on the realities of “prey pressure” that exist. Effective site sanitation, a prey management plan and direct treatment of the spiders and their harborages will provide results customers will value.

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