- This seventh annual report outlines our continued progress on each of six
Improved fumigants: We continue to evaluate previously established field
tests, which inlicate that chioropicrin continues to protect Douglas-fir poles
after 17 years and piling after 12 years. Vorlex treated poles are being
gradually recolonized by decay fungi, while the Vapam treated poles appear to
have little resistance to decay fungi. The latter poles were retreated last
summer and will be used to determine the effectiveness of fumigant
retreatment. Solid methylisothiocyanate (NIT) continues to protect Douglasfir
poles, although the 20 percent NIT treatment has experienced slightly
higher levels of colonization after 9 years. Additional tests to evaluate the
effectiveness of gelatin encapsulated MIT or chioropicrin indicate that both
chemicals continue to remain effective. In addition, there now appears to be
little difference between the levels of control exhibited following addition
of varying amounts of water to the poles along with gelatin encapsulated NIT.
Closed tube bioassays indicate the chioropicrin remains at fungitoxic levels
after 17 years, while no volatile fungitoxins appear to be present in Vapam or
Vorlex treated wood.
The evaluation of untreated Douglas-fir posts treated with NIT,
chloropicrin, or Vapam indicate that fumigants can not ccatletely protect
untreated wood in ground contact unless there is sane other type of
preservative treated barrier present. Although the NIT treatment provided the
best protection, all of the posts experienced some surface decay and termite
attack after 10 years. These results appear similar to those found with more
recent tests of posts treated with various coLthinations of preservative
containing wraps and fuinigants.
Evaluation of Mylone and tridipain, two solid chemicals that degrade to
produce NIT, initcates that NIT production and fungal control are enhanced by
the addition of basic pH buffers; however, only the pH 12 buffer resulted in
rapid fungal control. These results Jnitcate that the rate of fumigant
release can be tailored to control specific decay problems.
We have also investigated the decomposition of Vapam in wood. As
previously reported, there are over 14 potential deccmposition products from
this chemical. This past year we developed methods for assaying these
chemicals, evaluated the long-term stability of each, and prepared test blocks
for evaluating decc*,osjtion in wood. In addition, we have studied the
migration of volatile compounds from Vapam and NIT treated blocks under
controlled aeration. After 5,000 hours, detectable levesis of NIT, carbon
disulfide, and carbon oxysulfide are still present in air surrounding the
Douglas-fir blocks. These tests indicate that low levels of volatile
chemicals are continuously eninitted from fumigant treated wood. While this
poses little difficulty for utility poles, it may pose some hazard for wood in
closed spaces. Evaluations will continue until the emission levels decline
below detectable limits.
In addition to Vapam deccmposition studies, we have also evaluated the
decoxrosition, movement and fungitoxicity of NIT under a variety of
environmental conditions. In general, wet wood held less NIT, but the degree
of control produced was more rapid. These results suggest that dry wood will
act as a reseivoir of NIT, which will be released as moisture enters and
swells the wood. This effect may provide an excellent long-term decay control
strategy. The information from these studies will be used to develop more
ecific recaimrndations for fumigant treatment.
Cedar Saood Decay Control: This past year we reestablished the field test
of promising nei pentachiorophenol replacements, incorporating 26 chemicals
into these tests. These saitles will be evaluated after 1 and 2 years to
determine efficacy. In addition to the field test, we evaluated 13 new
formulations or cinations of formulations in our laboratory screening
tests. A nuner of chemicals including Isothiazolone, Amical 48 and a nurrer
of quaternary aimnonium compounds appear promising and have been included in
the field test.
Bolt Hole Decay Prevention: Test established 5 years ago to determine the
effectiveness of sprays, liquids or pastes applied to field drilled bolts
holes indicate that airanonium bifluoride, Boracol 40, and 10% penta provided
greater protection than Polybor or Patox washers. In addition, no evidence of
corrosion was associated with any of the treatments.
Fumigant treatments below the bolt holes continue to eliminate decay fungi,
although samples removed from further down the pole indicate an incoIr)1ete
distribution of MIT. These tests will be reevaluated this coming year.
Detecting Early Decay and Estimating Residual Strength: We continue to
evaluate the use of fluorescent coupled lectins and infra-red spectroscopy for
detecting fungi in wood and early decay under controlled laboratory
We have also continued evaluation of longitudinal compression (L) as a
measure of ultite wood strength using a series of 27 Ldgepole pine posts.
While the dense knot clusters interferred with the analysis, LCS, in
combination with other parameters, was a reasonably good predictor of bending
strength. These tests will continue with more uniform material.
In addition to tests of LCS, we have evaluated the ability of small scal e
tests to determine the strength of various wood pole connectors. Out results
were in close agreement with those obtained using full scale tests aii
illustrate the value of using small r1 e tests to develop strength
Initiation of Decay in Air-Seasoning Douglas-fir: We continue to evaluate the
data developed in the air-seasoning st1wies. This past year we began to
develop information on the effects of various colony sizes on wood strength.
This data will help us assign strength values to the colony size data we ha
developed frau the air-seasoning study. At present, only Peniophora spp. has
been tested, but . carbonica, P. placenta, and Haematostereum sanguinolentuin
will also be included.
Evaluation of the teinperatures required to eliminate fungi from Douglas-f ir
poles also continue. We have ccatpleted 9 test charges which indicate that the
penta treatmants involving a Boulton-seasoning cycle result in a ixre than
adequate heating of the wood, while steam treants associated with
amnniacal copper arsenate are nre variable. We feel that longer heating
periods are required for poles greater than 12 inches in diamater, but that
the current 6 hour steam period will result in heating of the center to 67 C
for over 1 hour in smaller poles.
Microfungi in Douglas-fir Poles: We continue to evaluate the effects of
nticrofungi on properties of fumigant treated Douglas-fir poles. These tests
indicate that prior colonization of fumigant treated wood by Scytalidium or
Trichoderma species resulted in lower weight losses by P. placenta and .
Evaluation of a Cellon treated Douglas-fir laminated beam indicated that
severe penta depletion was associated with virtually all of the surface decay
present. This beam had only been in service for 12 years in an extremely dry
climate arxl it is unclear why the decay was so rapid.