Label directions for applications of individual fumigants must be followed. In general, starting at
the ground line, a 5/8 to 7/8 inch diameter hole is drilled directly towards the center of the pole at a
steep downward angle. The hole should not be through the pole or intersect seasoning checks
which would allow the fumigant to escape. Additional holes to obtain good distribution of the
fumigant are equally spaced (and drilled in a downward direction) around the pole in an upward
spiral pattern with a vertical spacing of 6 to 12 inches. If more than two treating holes intersect an
internal void or rot pocket, redrill the holes further up the pole into relatively solid wood where the
fumigant will gradually volatilize and move through the wood. The fumigant placed in rot pockets
will be lost if the seasoning checks connect the pocket to the outside of the pole. If the rot pocket is
above the ground line, holes should be bored above and below the pocket. A three inch long treated
plug is inserted into each hole.
Fumigant applicators must wear protective clothing and should stand upwind. The proper amount
of the chemical is slowly squeezed into the lowest hole first, leaving enough space for the plug. A
tight fitting preservative treated plug is driven into the hole. Care must be exercised not to squirt
fumigant from the hole. The applicator continues to work up the pole one hole at a time.
Decay fungi reinvade vapam treated poles in about five years, but the fungal population remains
low for at least nine years. These poles should be retreated every nine years by placing additional
fumigant in the same hole. Because poles treated with chloropicrin and with Vorlex have remained
virtually free of decay fungi for 8 years, retreatment may be delayed ten or more years.
The effectiveness of wood fumigants for long term insect control is uncertain. Vapam may control
subterranean termites, however, carpenter ants are known to reinfest wood shortly after fumigant ap-
plication, perhaps because of the decreased fumigant concentration.
NAVFAC TS-20312 provides the following instructions for pole fumigation:
FUMIGATION: Serviceable poles which cannot be properly excavated around the entire cir-
cumference for causes beyond the contractor's control such as concrete, macadam, tree roots,
etc., or found to contain internal voids caused by decay and insects shall be fumigated in lieu of
typical digging/preservative treatment upon concurrence of the QAE. All such poles will be
sounded with a hammer in accordance with paragraph 3.1, Section 00005. Excavated poles will
be further sounded in accordance with paragraph 3.3, Section 00005.
Three quarter inch diameter holes shall be drilled at 45 angles or steeper into the pole. Each
hole shall be at least 15 inches deep. The first and last holes shall be drilled one foot beyond in-
cipient decay or voids. The drilling pattern shall have holes spiraled around the pole ap-
proximately 90 degrees from the previous hole, and 6-12 inches above the nearest lower hole.
An EPA registered pole fumigant containing 32.7 percent Vapam (sodium N-methyl dithiocar-
bamate) shall be poured into all holes at the rate specified on the label. Void treatment of poles