|Abstract or Summary
Chioropicrin, Vorlex and Vapam continue to control internal decay of
pressure-treated Douglas-fir poles 12 years after application. Fungitoxic quantities
of chloropicrin are present in the wood as high as 2.4 m (8 feet) above
the groundline. Solid methylisothiocyanate (MIT), which goes directly to a vapor,
is somewhat more effective in controlling decay than is Vorlex MIT is the active
ingredient of Vorlex.
Gelatin capsules containing chioropicrin or MIT offer new opportunities for
improved fumigation of poles. MIT is readily released in moist wood, but
chioropicrin capsules require wetting after they have been placed in the wood or
they must be mechanically ruptured for maximum effectiveness.
Although chioropicrin and MIT are adsorbed by wood after adequate aeration,
the fumigant-treated wood may be attacked by decay fungi.
Encapsulated MIT, is being compared to Vapam in pressure-treated Douglasfir
transmission poles near Buffalo, NY.
Controlling decay of cedar sapwood
Six decay fungi have been identif led from sapwood and three from heartwood,
of decay in cedar poles.
Five waterborne chemicals have been selected as potential substitutes for
the 10% pentachlorophenol-diesel oil solution currently used to spray cedar sapwood.
Of these, 3-iodo-2-propynyl-butylcarbamate equalled or exceeded the pentachlorophenol
solution in effectiveness at depths to 15 mm in the endgrain of
Seven chemicals judged to be the most promising were applied to cedar poles
at the Northwest Forest Genetics Center last fall. Other promising chemicals
detected by a bioassay will be applied to poles this summer.
Twenty-eight Douglas-fir poles 18 feet long were Boulton dried in a
pentachlorophenol-heavy petroleum solution, drilled with 8 alternating 3/4-inch
and 1-inch diameter holes in a spiral pattern and installed at the Northwest
Forest Genetics Center. Dry or liquid waterborne chemicals with low mammalian
toxicity or a 10% pentachlorophenol solution were applied in the holes before
the bolts were inserted. Patox washers between the pole and crossarm attachment
also are being tested.
Cores will be removed below unprotected bolt holes in control poles and
cultured for decay fungi as a guide for removal of cores below protected bolt
Detecting decay and estimating residual strength.
Testing plugs from Douglas-fir poles for radial compression strength (RCS)
was more promising than chemical tests that coloreçl the wood or a needle-scratch
test for detecting early decay. RCS, which measures the strength of the weakest
springwood layer was highly correlated with weight loss caused by Poria placenta,
an important brown-rotter of Douglas-fir poles. RCS losses were detected
before weight losses could be measured. Sapwood was lower in RCS than heartwood,
probably because of differences in extractive content of cell walls.
Infrared spectographic analysis of dried warm water extracts from wood beams
decayed to low weight losses and tested in bending is being evaluated as a means
of detecting early stages of decay that might cause significant strength losses.
As a means of estimating residual strength of poles, RCS values, bending
strength properties, toughness and sonic properties of small beams cut from pole
sections exposed at the four Northwest air-seasoning sites are being evaluated.
Decay of Douglas-fir poles prior to pressure treatment
Fourteen cores were removed from 229 unpeeled poles and 752 peeled poles
stored in seasoning yards from 0 to over 24 months and cultured for fungi. About
50% of the probable decay fungi isolated from the cores have been identified.
Atleast 30 of the unpeeled poles (13%) contained decay fungi. The incidence of
decay fungi, especially Poria carbonica, increases significantly as the air
seasoning time is prolonged. This summer cores will be removed from freshly cut
poles in the forest and from additional poles during air seasoning, especially
those seasoned for over 1 year.
Laboratory studies indicate that spores and fungal fragments, alone or
attached to soil particles and air borne, play an important role in the infection
of poles. Exposure of sterilized pole sections at the four Northwest air
seasoning sites for successive 3-month periods indicates that infection
increases dramatically during the November-January period at three sites.
borne spores appear to play an important role in the infection