Syngenta Professional Pest Management: Spiders

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, pest management professionals (PMPs) should start by identifying the spider species, and then engage both chemical and physical controls to remove spiders from their customers’ property. The following information explains how to use these techniques to create an effective spider control program.

• Inspection and identification: A thorough inspection of both the inside and outside of a building is critical to determine the types of spiders, their entry points and the sources of infestation. Although spiders can be difficult to identify without certain tools and practice, properly identifying widow and recluse spiders is important if customers have an alleged spider bite. As you may know, most widow spiders have red markings on a shiny black body, and recluse spiders generally have a violin-shaped marking on a brown body. You can find several useful resources online and in print for identifying other varieties of spiders.

• Chemical controls: Insecticides are effective when applied to areas of spider harborage and activity as a spot or crack-and-crevice treatment.

• Physical controls: In addition to chemical controls, physical controls can be effective methods for controlling spiders. 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 the removal of any harborage areas. This can include cleaning areas of webs and egg sacs by vacuuming, flushing and other general sanitation efforts. In addition, 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.

With the exception of widow and recluse spiders, most spiders do not cause harm to humans, structures or food supplies, but homeowners tend to be more comfortable if they are fully controlled. If widow or recluse spiders are identified on a customer’s property, suggest sanitation and maintenance tips to prevent future injuries from these venomous species. Inspecting stored boxes, cutting tall grass and storing debris off the ground will eliminate hiding spaces for these spiders.