by Mike Potter, Extension Entomologist
University of Kentucky College of Agriculture
The Entomology Department often receives calls from people wanting to know what can be done to protect their home from termites -- or if a certain practice or condition is likely to cause termite problems.
Homeowners can reduce the risk of termite attack by following the suggestions listed below.
- Eliminate wood contact with the ground. Many termite infestations result from structural wood being in direct contact with the soil. Earth-to-wood contact provides termites with easy access to food, moisture, and shelter, as well as direct, hidden entry into the building. Wood siding, latticework, door and window frames and similar wood items should be at least six inches above ground level. Eliminating wood-to-soil contact may require regrading or pulling soil or mulch back from the foundation, cutting the bottom off of wood latticework, or supporting steps or posts on a concrete base. Posts or stairs that are embedded in concrete are also vulnerable to termites since they usually extend all the way through the concrete to the soil. Contrary to popular belief, wood which has been pressure treated is not immune to termite attack; termites will enter pressure-treated wood through cut ends and cracks, and will also build tunnels over the surface.
- Don't let moisture accumulate near the foundation. Termites are attracted to moisture and are more likely to "zero in" on a structure if the soil next to the foundation is consistently moist. Water should be diverted away from the foundation with properly functioning gutters, downspouts and splash blocks. Leaking faucets, water pipes and air conditioning units should be repaired, and the ground next to the foundation should be graded (sloped) so that surface water drains away from the building. Homes with poor drainage may need to have tiles or drains installed. Lawn sprinklers and irrigation systems should be adjusted to minimize water puddling near the foundation.
- Reduce humidity in crawl spaces. Most building codes call for 1 square foot of vent opening per 150 square feet of crawlspace area. For crawlspaces equipped with a polyethylene vapor barrier (see below), the total vent area often can be reduced to 1 square foot per 300 to 500 square feet of crawlspace area. One vent should be within 3 feet of each exterior corner of the building. Vents should be kept free of leaves, dirt, and debris, and should not be obstructed by vegetation. Moisture and humidity in crawl spaces can further be reduced by installing 4-6 ml polyethylene sheeting over about 75 percent of the soil surface. The soil cover will act as a vapor barrier to reduce evaporation from the soil and condensation of moisture on joists and subflooring. Vents and vapor barriers are installed by most pest control companies.
- Never store firewood, lumber or other wood debris against the foundation or inside the crawl space. Firewood, lumber, cardboard boxes, newspapers, and other cellulose materials attract termites and provide a source of food. When stacked against the foundation they offer a hidden path of entry into the structure and allow termites to bypass any termiticide soil barrier which is present. Vines, ivy, and other dense plant material touching the house should also be avoided. Where practical, dead stumps and tree roots around and beneath the building should be removed, along with old form boards and grade stakes left in place after the building was constructed.
- Use mulch sparingly, especially if you already have termites or other conducive conditions. Many people use landscape mulch for its aesthetic and plant health benefits. Excessive or improper usage, however, can contribute to termite problems. Termites are attracted to mulch primarily because of its moisture-retaining properties, and the insulation it affords against temperature extremes. The mulch itself is of poor nutritional quality to termites and a non-preferred source of food. Since the moisture retaining properties of mulch are more of an attractant than the wood itself, it makes little difference what type of mulch is used (cypress, pine bark, eucalyptus, etc.). Contrary to popular belief, crushed stone or pea gravel are comparable to wood mulch in terms of attraction, since they also retain moisture in the underlying soil. Where mulch is used, it should be applied sparingly (2-3 inches is usually adequate), and should never be allowed to contact wood siding or framing of doors or windows.
- Consider having the structure treated by a professional pest control firm. Buildings have many natural openings through which termites can enter, most of which are hidden. While the above measures will help make the house less attractive to termites, the best way to prevent infestation is to protect it with a termiticide.
Preventively treating a home for termites is a reasonable investment, especially if the structure has had no prior history of treatment. If the building was previously treated by a pest control firm, it's a good idea to maintain the warranty by paying the annual renewal fee. Should termites reinfest the building (which can happen even if the initial treatment was performed correctly), the company will return and retreat the affected area at no additional charge.
Whether or not a person chooses to have their home treated, they should know the signs of termite infestation:
Pencil-wide mud foraging tubes on foundation walls, piers, sills, joists, etc.
Winged "swarmer" termites, or their shed wings, on window sills and along the edges of floors.
Damaged wood hollowed out along the grain, lined with bits of mud or soil.
Detecting hidden termite infestation requires a trained eye. Most pest control firms perform inspections free of charge and will also alert the homeowner to any conditions they uncover which are conducive to termite attack.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!