By Amanda Sears
We have had several calls recently about spiders in homes. This is a common problem this time of year. Typically, the caller wants to know if the spider they’ve seen is dangerous and what if anything should be done in terms of control.
The vast majority of spiders are harmless, and in fact are beneficial, because they prey upon flies, crickets and other insects. They generally will not attempt to bite humans unless held or accidentally trapped. Moreover, the majority of spiders have fangs too small or too weak to puncture human skin. Of the hundreds of species found in Kentucky, only the black widow and brown recluse are dangerous. Fortunately, both are relatively uncommon, and have markings which can be used to distinguish them from other nonthreatening species.
General Control Measures (all species)
1. Routine, thorough house cleaning is the most effective way to eliminate spiders and discourage their return. A vacuum cleaner and broom are the householder's most useful tools for removing spiders, webs and egg sacs.
2. Spiders prefer quiet, undisturbed areas such as closets, garages, basements and attics. Reducing clutter in these areas makes them less attractive to spiders.
3. Large numbers of spiders often congregate outdoors around the perimeter of structures. Migration indoors can be reduced by moving firewood, building materials and debris away from the foundation. Shrubs, vines and tree limbs should be clipped back from the side of the building.
4. Install tight-fitting window screens and door sweeps to exclude spiders and other insects. Inspect and clean behind outdoor window shutters, and inside the orifices of gas barbecue grills.
5. Consider installing yellow or sodium vapor light bulbs at outside entrances. These lights are less attractive than incandescent bulbs to night-flying insects which, in turn, attract spiders.
6. To further reduce spider entry from outdoors, insecticides can be applied as a “barrier treatment” around the base of the foundation. Pay particular attention to door thresholds, garage and crawl space entrances, including foundation vents. Sevin, Dursban or any of the synthetic pyrethroids, e.g., Spectracide Bug Stop (tralomethrin), Ortho Home Defense System (bifenthrin) are effective, but may need to be reapplied periodically. Just be sure to read the label as to how often the treatment should be applied.
The management tips above work for both the average everyday spider as well as those which are venomous to us. Removal of unnecessary clutter is especially helpful in making areas unattractive to these pests.
If you have tried to control spiders with all the tips above and still have a problem, or have a severe infestation of brown recluse or black widow spiders, you should call a professional pest control firm.
They have access to chemicals that are stronger than a homeowner can obtain as well as experience and expertise that make them able to better handle especially strong infestations.
Educational programs of the University of Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.