Termites Control: Borates
Borates can be used to control a variety of wood destroying pests, such as termites, carpenter ants, carpenter bees and fungus. And are actively used for termites control - http://advancedpest.com.sg/termite-solutions.html. Bora-care and Timbor are 2 of the most popular borate formulations used for home pest control. The character of borate products in general is to be toxic when ingested, and this is what the insects and fungi are doing when they bore in wood. The exception would be carpenter ants which do not eat the wood but merely excavate cavities and toss the wood chips away. However, they must get enough of the borate into their system by ingestion to have some effect. Borates are toxic only by ingestion, and have no contact or desiccant properties. Another benefit of the active ingredient is that it essentially lasts forever. Borates, which are found in Tim-bor and Bora-care are refined from borax, which is a mineral mined from the soil, and as a mineral it simply does not quickly degrade.
Unless it is physically removed from the wood in some manner, borates will remain in place and active for many years, providing protection when first applied. Borates are highly soluble in water, so a powder formulation like Tim-Bor cannot be used where rainfall or irrigation will wash it off the treated wood, as the active ingredient does not penetrate beyond a fraction of an inch. Bora-Care, on the other hand, is formulated with solvents which, according to the manufacturer, cause it to be moved deep into the wood. Here it not only is not exposed to rainfall, and thus can be used on some exterior woods, but it also takes the borate active ingredient into the feeding zone of the insects. The best you can hope for with borates that rest on the wood surface is to affect the adult insect as it bores out of the wood, such as beetles will do. With a borate that penetrates, like Bora-care, you stand a good chance of killing the feeding larvae or termites that are eating through the wood well inside.
There is no doubt that borates will kill any insect eats them, or fungi that feed on treated wood, once the material does penetrate then it definitely will be effective as a "post" treatment, or eradication of an existing infestation. Ideally you can Pre-treat for termites control. You can apply the liquid solution quickly and easily with little concern for finished surfaces. For Post-treatments you are only permitted to treat unfinished wood materials, so applying borates over paint or clear finishes is not feasible or effective. In what I would consider the normal definition of Post-treat you would be treating a structure after it is completed, different from treating to control an existing infestation. Pre-treating is also ideal because it covers the susceptible wood with that toxic layer so that any pest attempting to get started in that wood must eat through the borate layer to get inside, killing it early on.