Basic knowledge of pests and their biology is necessary to avoid use of toxic methods of control. The "bible" of IPM is Common Sense Pest Control by William Olkowski, Sheila Daar, Helga Olkowski published by The Taunton Press, 1991.
Old-fashioned methods such as installing a birdhouse for Purple Martins can help encourage natural insect control. Organic pest control such as insecticidal soaps and manual methods such as pulling weeds or using sand barriers and termite shields are time-tested and non-polluting. Beneficial insects such as ladybugs and beetles can be introduced into the landscape.
Difficult problems such as fire ants can be tackled with compost tea treatments and growth regulators containing fenoxycarb.
To properly implement IPM after your building is built, an IPM plan should be written and included in the operations manual for a building or owner's manual for a house. The City of Austin has an IPM expert with templates for what these plans should include. Call John Gleason at 974-3543 for more information.
Most areas of Texas have termites, including subterranean termites that live in the soil and drywood termites that attack dry wood. According to the Texas Agricultural Extension Service, there is a greater than 70 percent probability that a wooden structure in Texas will be attacked by termites within 10 to 20 years. Termite problems within one year after construction have been reported.
When wood is used as a building material, termite prevention in the form of treated wood or naturally resistant wood will be required by building codes. Typically, chromated copper arsenate (CCA) pressure-treated wood is used. Two alternative chemical substances have gained popularity since more toxic substances such as chlordane have been banned for soil treatment. These include organophosphates and pyrethroids. However, these chemicals are toxic to people as well as termites, and can offgas and leach into the soil and water table. They can be absorbed through the skin, lungs and through ingestion. Small children, workers, chemically sensitive individuals and animals can experience serious health problems when exposed to them.
Less toxic wood treatments are available. However, alternatives to wood treatment and chemical treatment can be quite effective. Least-toxic strategies must be used in combination to achieve maximum effectiveness. Few pest control managers expect non-toxic methods to completely replace chemical use. However, they allow for the reduction of chemical use, and may prevent such use in all but extreme situations.
The only sure prevention of termite problems is the use of building materials other than wood. However, if wood is used, there are preventative measures available to the builder other than chemical treatments and treated wood products.
A common tree in Austin known to resist termites is the familiar mountain cedar (actually a member of the juniper family). Although not commercially lumbered, old growth natural cedar posts have traditionally been used as foundation piers on old structures, for fences, and for furniture. The use of juniper wood has some potential for application as a termite and insect resistant wood.
Eliminating sources of chronic moisture in the home is one of the most important factors in managing subterranean termites, carpenter ants, and some wood boring beetles. Moist soil is necessary for termites to survive. Termites travel back and forth between soil and food sources because they must obtain moisture from the soil. In addition, capillary action and water vapor buildup can result in excessive dampness, which can actually wick through a concrete slab or masonry foundation to the wood framing above it, thus attracting termites.
In aboveground foundations, moisture barrier films such as 6-mil polyethylene can be used to cover the area under the structure. This will help decrease moisture buildup in sub-flooring. Foundation wall vents should be placed to provide cross ventilation for homes with crawl spaces. Some experts also recommend the use of moisture barriers under slab foundations.
Soil should always be from 12 to 18 inches below any wood member. The greater the distance, the better. Good siting and drainage design will help prevent moisture buildup in and around the structure, as will effective guttering and downspout location. All exterior grades should slope away from the structure to provide drainage. Porches and features such as planter boxes should be constructed and sealed to prevent moisture and soil contact with the structure.
Exterior landscaping should not cause moisture build-up around the foundation. A small air space should be retained between plant leaves and walls to prevent moisture and mold build-up. Work to avoid putting plantings too close to the foundation walls. A three-foot minimum distance is a good rule of thumb to use, and in addition, keep in mind a plant's mature size. Automatic irrigation heads should be properly aligned or shielded to prevent direct spray onto the building.
Areas subject to moisture build-up and water leaks, such as bathrooms, kitchens and laundry areas, should be given special attention since they are likely to be attack areas. Areas under tubs and drains leading to the exterior (such as air conditioner drains) should be considered vulnerable spots.
All wood-to-soil and wood-to-concrete contacts should be eliminated for fence and deck posts, porch posts, stair stringers, rail supports, trellises, pergolas, etc. Posts should be placed in metal holders (commercially available). Even treated deck piers may not deter termites since they may bypass the treated piers to reach untreated decking above.
All wood subject to moisture, especially exterior wood, should be properly sealed. Exterior windows, even if under an overhang such as a porch, should be completely moisture sealed. Exterior siding, especially along the bottom wall edges, should be completely moisture sealed on all exposed surfaces.
All lumber scraps, wood debris and stumps should be removed from the site after construction is complete. Backfill under a foundation should never contain wood scraps, and scrap should never be left in crawlspaces or under foundations. Such scraps are invitations to termites to eat the scrap and then move on to the main structure.
Sand barriers for subterranean termites are a physical deterrent because the termites cannot tunnel through them. Sand barriers can be applied in crawl spaces under pier and beam foundations, under slab foundations, and between the foundation and concrete porches, terraces, patios and steps. Other possible locations include under fence posts, underground electrical cables, water and gas lines, telephone and electrical poles, inside hollow tile cells and against retaining walls.
Sixteen grit sand or cinder is placed in a 20-inch band on the soil surface or in trenches next to foundation walls. The sand layer should be 4 inches thick at the foundation, and feathered out to meet grade at the outer edge of the 20-inch band. For trench installations, trenches should be 4 inches deep and 6 inches wide.
Some integrated pest management experts have developed a machine called a sand pump that blows sand under the house. For sand barriers around the outside perimeter of a foundation, they recommend a sand trench in order to avoid disturbance of the sand. In addition, a cap made of masonry or other materials may be recommended to protect the barrier from gardening or animal disturbance. Tamping of sand increases impermeability to termite attack.
Slab Barriers
Termites can easily pass through cracks, as small as 1/32 inch, which may occur in slab foundations. For sand barriers in conjunction with slab foundations, the sand or cinder must be applied before the foundation is poured. Installing the sand layer of the appropriate mesh size followed by a layer of coarser gravel for grading to the desired level works well. To cut costs, sand treatments may be installed in particularly vulnerable areas of the slab, such as around pipe penetrations, as opposed to under the entire slab.
Costs for cinder fill under a slab can often be competitive with the costs of standard fill and the initial chemical termite treatment.
Sand Selection
The size of sand particles is critical to the success of sand barriers . Sand or grit size should be siftable through a 16-mesh screen. Sand smaller than 16-grit can be carried away by termites and larger sand can support their tunnels. If the sand to be used has some particles smaller than 16-mesh size, it should be screened with mesh of the appropriate size. Certain grades of sandblasting sand may be suitable for barriers. Crushed volcanic cinder of the appropriate size can also be used.
Performance
Sand barriers can also be used to repair broken seals between foundations and other building elements such as porches. Such settling and breaking of "cold" joint seals can be caused by subsidence and temperature extremes. In laboratory tests, sand was shown to retain its "seal" against structural members after movement similar to earthquakes. Although earthquakes are not a problem in our area, soil movement and settling because of expansive soils is often a problem.
Use of sand barriers is still experimental, and must be followed with post-installation and regular subsequent inspections.
Metal termite shields are physical barriers, which prevent termites from building invisible tunnels. In reality, metal shields function as a helpful termite detection device, forcing them to build tunnels that can be easily seen on the outside of the shields. Metal termite shields also help prevent dampness from wicking to adjoining wood members, which can result in rot, making the material more attractive to termites and other pests.
Metal shields are used in conjunction with concrete or solid masonry walls, and are fabricated of sheet metal, which is unrolled and attached over the foundation walls. The edges are then bent at a 45-degree angle. Metal shields must be very tightly constructed, and all joints must be completely sealed . Any gaps in the seals will allow an entry point for termites. Joints may be sealed by soldering, or with a tar-like bituminous compound.
Metal flashing and metal plates can also be used as a barrier between piers and beams of structures such as decks, which are particularly vulnerable to termite attack.
Stainless Steel Barriers
Stainless steel barriers incorporate finely woven, marine grade, stainless steel mesh, which can be used in the same manner as the traditional metal shield. The mesh is also placed around all plumbing pipes that penetrate through the slab as well as through the "cold joints" of concrete pours.
The grid pattern of the mesh is fine enough to not allow termites through, but is strong enough to prevent them from chewing through it. Being stainless steel, it is unlikely to be affected by the corrosive nature of some concrete and ground conditions. A stainless steel mesh termite barrier system is now available in Texas.
The Bio-Integral Resource Center (see Resources, General Assistance) recommends the following steps:
- Monitor the building at least once per year.
- Identify the species of termite.
- Correct structural conditions that led to the infestation.
- Apply physical or biological controls.
- Spot treat with chemicals if necessary.
- Check for effectiveness and repeat if required.
Regular annual or biannual termite monitoring should be done with a plan of the structure in hand. This will help to identify areas that may be hard to spot with a visual inspection.
Subterranean termites build characteristic mud tubes for movement between nests. The appearance of these tubes is often the first sign of infestation. Detection can become difficult if such tubes are hidden inside walls, or termites are entering in cracks occurring in concrete slabs or foundations.
Dogs trained to detect termites and other wood damaging insects are being used to aid in termite inspection. Their keen sense of smell coupled with their ability to wriggle into areas too small for human access can make the dog-assisted inspection a valuable tool.
The first step in any termite treatment is to accurately identify the species. Then locate nests. And, select a combination of least toxic strategies and tactics.
When selecting a pest management company, be sure to choose a reliable firm. Texas law requires commercial pesticide applicators to be certified. Check for certification documentation, references, and work experience, or check with the Structural Pest Control Board of Texas. Ask if the company practices integrated pest management techniques, or has an experimental license, which may be necessary for some alternative techniques.
Non-toxic treatments include use of nematodes (microscopic worms), especially for chemically sensitive individuals or environmentally sensitive areas. Nematodes are pumped into the infested area, where they will kill the insects. Boric acid bait blocks can be placed around the structure, where they will attract the pests to consume termiticides without broad application of chemicals.
Drywood termites can be treated with thermal, freezing, or electrical eradication techniques. Desiccating dusts, non-toxic substances resulting in pest dehydration and death, have also been used successfully on drywood termites.
These treatments can be combined with others, such as installing metal shields (if they have not been used previously), sealing broken seals or open areas, and re-grading soil outside the foundation to improve drainage or create a gap between soil and wood areas such as siding. In addition, termites can be physically removed by trapping or nest excavation. |