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Windows & Doors
Fungi and Insects Feast on Wood
The two principal organisms responsible
for destroying wood are fungi and insects.
Fungi are microscopic organisms that
consist of threadlike structures and depend on organic matter
for food. There are three types of wood fungi:
- Mold: grows on the surface
of wood, consuming sugars and other carbohydrates. It gives
the wood a ‘woolly’ or powdery appearance but
does not affect timber strength.
- Sapstain: these fungi are
pigmented and discolor or stain infected timber. Sapstain
fungi don’t affect timber strength but do make small
holes in cell walls and membranes, making it more susceptible
to rot.
- Decay: is the most destructive
form of fungal attack. Three types occur: brown, white and
soft rots. These utilize the cellulose and lignin in cell
walls, quickly weakening timber strength.
Insects involved with wood destruction
are, generally, either termites or beetles. However, wood
wasps, moths and carpenter ants are problems in some areas.
Insects feed on wood, damaging it by chewing and boring into
it. Some insects do negligible structural damage while others,
such as termites, can leave only a thin outer shell of wood,
the inside being completely hollow.
In 1931, a Defense was Mounted
Chlorinated phenols, principally pentachlorophenol
(penta or PCP), were one of the earliest preservatives used
in protecting millwork from decay. This solvent-based system
was introduced to the millwork industry in about 1931. Chlorinated
phenols were highly effective, but for environmental reasons,
the EPA in 1986 restricted the use of PCP.
Today, hundreds of sites across the country,
like that of the former Penta Wood Products treatment facility
south of Duluth, Minn., are under remediation. A 1987 investigation
of the Penta site disclosed that groundwater at the site was
contaminated with PCP. About 4,800 tons of arsenic-contaminated
soil (from related ammonia copper arsenate use) have been
excavated and a groundwater treatment program, expected to
last up to 30 years, was begun this summer.
One brand name that became synonymous
with penta was “Woodlife.” In 1984, due to pending
EPA restrictions, 3-iodo-2-propynyl butyl carbamate, commonly
referred to as IPBC, replaced penta as the fungicide in Woodlife,
and is still used today by many in the millwork industry.
IPBC is not an effective insecticide, however. An insecticide,
“chlopyrifos,” is commonly added to Woodlife for
pest control. The newest version of Woodlife uses a petroleum
solvent as a carrier for the active ingredients. It is commonly
applied using the dip system.
Penta was a very effective decay preventative,
and since its ban, manufacturers say that they have seen a
“creeping” increase in incidents of wood decay.
Another treatment product, Pilt, which
used Tri-N-Butyltin Oxide (TBTO), became available in 1976.
Pilt is an acronym for preservative in-line treatment. Like
Woodlife, it uses a solvent-based dip system. In 1990, IPBC
largely replaced TBTO.
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