Misconceptions Still Exist Concerning Borate Uee

The source of much of this information is researcher Dr. Jeff Lloyd, manager of preservation technology for Borax Europe Limited, who came from Guildford, England, to make a presentation at the workshop.

DRYWOOD TERMITES INFEST ONLY DRY WOOD? Not so. Although the name suggests otherwise, drywood termites actually require some moisture in order to successfully colonize timber and cause commercially significant damage. This is why they are generally only found in hot countries near the coast or in the tropics — areas combining warm ambient temperatures with high relative humidity. Air-conditioned houses in Florida, in which air conditioning units can reduce moisture content to as little as 7%, do not provide ideal conditions for drywood termites. This lack of interior moisture is one of the reasons they are more commonly found in exterior millwork, such as window frames, soffits, attic timbers and framing. Typically the moisture content of these timbers is at or above 12% moisture.

Drywood termites can also cause significant damage at a much higher moisture content. However, other wood destroying pests are usually found in these areas because they are able to colonize in these areas much more quickly. Subterranean termites are able to modify the moisture content of the timber they are colonizing and do not survive well without access to a moisture source. Typically this source of moisture is free water in the soil or from a source above grade. Drywood termites, on the other hand, rely more heavily on air humidity and may even be able to create metabolic water from carbohydrate and cellulose breakdown.

BORATE MOVEMENT NULL IN LOW MOISTURE. Some pest controllers may think that although a borate readily diffuses in wood with a moisture content of 20% or higher, it continues to diffuse, albeit more slowly, at levels as low as 7% or 8%. Wrong! In truth, the movement of borates at very low moisture content is not significant and the load of borate at the surface just stays put. This is one of the reasons it is recommended to drill and inject borates into known infestations, especially infestations of drywood termites. Solid borate products, such as rods, should never be used on wood that will remain relatively dry, as the borate will never be released or diffuse. On the other hand, they are excellent in areas of high moisture content, such as in the base of a fence post, poles or beams below grade.

Furthermore, it is also a myth conception that wetting the timber before spraying borate improves penetration. In fact, a superficial surface wetting prior to borate application will most likely reduce initial borate adsorption. If you want to maximize penetration, it is best to apply a coat of Tim-bor 10% solution to the dry wood, followed a half an hour later with a second coat.

A second application can carry initial borate loading to a depth in excess of 10 mm. Glycol borates, such as Bora-Care, are able to carry the boron further into very dry wood, although the best method is a foam application of borate. A foam application gives excellent penetration, and with a single application, offers the same loading in the wood that is achievable with a double application by spray.

A progress report issued in January 1998 of a 6-year experiment by T.L. Amburgey and Lonnie Williams at Gulfport, Miss., reported that subterranean termites were prevented from tubing over wood that was treated with a 1:1 dilution of Bora-Care.

It is important to know that even superficial treatment is still sufficient to kill termites or fungi that could attack the wood later. This is because termites bring moisture with them, and this moisture raises the overall moisture content of the wood. Dry wood placed inside a chamber at 100% relative humidity reaches a moisture content of 24%. Relative humidity in an active termite tube raises the moisture content of the wood and termites will feed on treated as well as untreated wood, ingesting a toxic dose.

IS FUMIGATION FLAWLESS? Many think that fumigation is a sure-fire panacea to control multiple sites of infestation by wood-destroying insects. Not always! Changes in new construction pose new problems. Plastic films, foam boards or non-permeable barriers are often incorporated into some elements of construction. Some new insulation materials contain a matrix that wicks water from soil and keeps the timber wet. On the other hand, if the structure is an old one without the new elements described above, fumigation rather than spot treatment should be recommended for wood- boring insects if there are more than three infested sites, according to veteran fumigator Gil Livingston. Remember, however, that the termites are free to return at any time so a follow-up treatment with borates is the permanent answer following any fumigation.

It is also commonly held that borate treatment for wood is a new development. Wrong! Borates have been widely used in Europe and elsewhere for decades. In New Zealand, wood-destroying organisms had been a major problem until soaking construction timbers in a borate solution was mandatory. This was introduced in 1953 and since that time there has been no single reported incidence of failure in these treated houses.

Harry Katz is a contributing editor to PCT.