Efforts to control spiders should initially focus on eliminating their habitats and other conditions that facilitate nesting and significant population levels. This involves physical removal of infestation sources such as firewood piles and clutter around the yard or in crawlspaces, as well as some landscaping changes such as eliminating grass or other groundcover against foundations. Once these initial steps are taken, insecticidal techniques can be considered.
Pest management professionals (PMPs) working in crawlspaces and other areas with significant numbers of these venomous spiders may wear protective clothing, including long sleeves tucked into gloves, a jacket or sweatshirt with a hood, and pant legs tucked into boots. Rubber bands or masking tape should be used over pant legs and sleeves, or over boots and gloves, to prevent spiders from crawling up onto the skin of arms and legs. Any clothing or other items stored in spider-infested areas should be carefully shaken out and inspected prior to use.
Indoor management of spiders may involve nothing more than vacuuming up the spiders and their webs and egg sacs. Removing clutter and taking other sanitation steps directed at conditions favoring spiders indoors, around or under the home, or in the landscape are necessary to help reduce spider problems. Thorough inspections are necessary to find all spider harborages for later sanitation, removal, or insecticide treatment.
Synergized pyrethrins, or other non-residual pyrethroids, are often useful for cleanouts and for eliminating outdoor species that may be found indoors. Long-term residual control of spiders is difficult to achieve. If spiders are established indoors or if outdoor species are migrating indoors, residual applications of one of the labeled pyrethroid insecticides, chlorfenapyr, acetamiprid, or silica aerogel can be used. All areas where the spiders have been found should be treated, paying particular attention to dark corners. Dusts are especially useful for treating inaccessible void areas, crawlspaces, and attics. Wettable-powder, suspension, or microencapsulated formulations will generally give somewhat better and longer residual action on most surfaces.
Outdoor treatment with residual pyrethroids or fipronil may be necessary to control spiders migrating inside or to eliminate spiders on or under porches, in crawlspaces, under eaves, and in other areas on the outside of the building. For some venomous species, such as the European house spiders or the black widow, insecticide applications may be necessary in landscape areas such as foundation plantings or rock gardens. Chronic spider problems often occur on exterior surfaces of homes and buildings built near lakes, where spiders spin webs to catch and feed on the many flying insects that come out of the lake and adjacent marshy areas. There are few good management options for chronic spider problems, except reducing night lights (which attract flying insects) and applying residual insecticide treatments at necessary intervals.
Spider fecal droppings can disfigure fiberglass boats or latex-painted surfaces, and area treatments may be necessary to eliminate heavy infestations. The residual insecticides just listed are also recommended for use outdoors.
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