ONLINE EXTRA: Managing Yellow Sac Spiders

Editor’s note: In Albert Greene’s October feature “The Arachnid Up My Nose (And Other Tales of the Yellow Sac Spider)" the author explored many facets of these fascinating creatures. The following online extra item features tips on how to manage these structural pests. It has been excerpted from the PCT Field Guide For The Management of Urban Spiders. This comprehensive book can be ordered HERE.

KEY MANAGEMENT STRATEGIES

A detailed control program will be needed only in cases where yellow sac spiders are involved. If other species of sac spiders are found inside a building, treatment of the exterior as described below will likely produce satisfactory results.

Contributing Conditions. The most important condition to address in reducing the threat of sac spider infestations is the removal of potential hiding places near the foundation of the building. Firewood piles should be moved as far from a house as possible and stored off the ground and covered with plastic to keep them dry.

All items lying on the ground such as piles of lumber and other debris, stones and boards should be removed from the property. Heavy vegetation such as ivy and other ground covers as well as branches of trees and shrubs should be cut away from the building. Completing these items also reduces the potential harborages for insects serving as the spiders’ food source.

Exclusion. Any crack in the exterior of a building through which spiders could enter should be sealed AFTER they have first been treated with a residual insecticide as described below. Sealing cracks that may harbor spiders before treating them may force the spiders inside the building. All vents, windows and doors should  have no cracks around them and should be equipped with screens. It is also important to seal cracks around pipes, wires and cables leading up into the structure from the crawlspace to the basement.

Buildings with brick veneer often have weep holes to allow moisture to exit from behind the veneer. These weep holes cannot be sealed, but small pieces of screening can be inserted into the weep holes to prevent spiders and other pests from entering. Screens designed for this purpose may be available commercially.

Sanitation. The silk retreats, as well as the spiders within them, should be removed. The sacs may need to be scraped out with a putty knife. Keeping a vacuum device handy allows quick removal of spiders and their retreats and a corner attachment for the vacuum will be useful. New activity in the future is easier to detect if webbing is removed. Removing potential outdoor harborages for spiders and sealing exterior cracks as previously discussed are both part of a good sanitation program for sac spiders.

Insecticide Applications. Inside, removal of sac spiders in their silken retreats by vacuuming will generally get most of the spiders. If a vacuum device is not available, treatment of spiders found using a directed contact treatment can be applied. The use of crack and crevice treatments and spot treatments with residual liquid insecticides may also be necessary.

Crack and void treatments. Cracks inside where sac spiders could enter the living ares of the building from inside walls should be treated with a residual dust insecticide. Cracks around plumbing pipes, light fixtures and air vents are examples of areas to be treated. Sealing the cracks after treatment is best as a long-term control strategy.

If a severe infestation of yellow sac spiders is encountered, removal of all of the plats covering electric outlets and switches and treatment of the wall void behind with a dust insecticide may be required. This treatment, however, would be rarely necessary for sac spiders.

In crawlspaces and basements, it may be necessary to apply dust insecticides into the cracks under sill plates and into the voids or foundation walls. This is particularly necessary for older buildings with stone or brick foundations. Dust insecticides can also be applied to the sill plate areas of crawlspaces.

Spot Treatments. The application of liquid residual insecticides to upper corners of rooms following removal of spiders can be helpful in many cases involving these spiders. Use a wettable powder or microencapsulate insecticide formulation for best results, although emulsifiable concentrate insecticides may be useful in some situations.

In crawlspaces and basements, spot treatments can be applied to the sill plate/box header area at the top of the foundation walls.

Directed Space Treatments. Nonresidual ULV insecticides can be effectively used to kill sac spiders found during inspections when applied as a directed space or contact treatment. Use these treatments when a vacuum device is not available to remove the spiders.

Exterior Treatments. The most important control measure for the outside areas is the removal of as many potential harborages as possible as previously discussed. This automatically reduces spiders and insects they prey on near the building.

Any exterior crack in the exterior walls of the building should be treated with a residual dust insecticide and then sealed to prevent spiders from entering in the future. Use a large hand duster to apply dust through weep holes and kill spiders that might be harboring behind the brick veneer.

Spot treatments with a wettable powder or microencapsulated insecticide around doors and windows may be useful in preventing new spiders from entering. A perimeter treatment may be applied to the foundation and ground away from the building.