Quantcast Biological Tests

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Pol-tek. The pol-tek is a sonic testing device that does not require boring.
Starting about six inches below the ground line, probes are pressed on opposite sides of the pole. A
trigger trips a hammer that sends a sound wave down one probe, through the pole, and up the other
probe where it is recorded. Rot or low density areas will delay the sound wave and result in a lower
reading than with a sound pole of the same diameter. The reading is nearly instantaneous. Boring
is done to determine the extent of decay in those poles with low readings. It is reported that the pol-
tek works well on Douglas-fir and Western red cedar, but not as well on southern pine because of
the high incident of ring shake.
New Technologies. Even newer technologies are being developed to
nondestructively estimate residual strength in standing poles. More field experience is required
before comment can be made on the practical utility of those devices in the field.
Shell Thickness Indicator. A shell thickness indicator (Figure 7-6) is used to
determine the thickness of the remaining wood. The rod is inserted into the hole made by coring or
drilling and then pulled back with pressure against the side of the hole. The hook at the end will
catch on the remaining sound wood. When pushing a tight fitting shell-thickness indicator into a
hole, you can feel the tip of the hook pass from one growth ring to another in solid wood, but not in
rotten wood. Marks may be inscribed on the side to indicate shell thickness at drilling angles of 45
and 90 degrees.
7.1.2.3 Biological Tests.  It is important that the presence of decay fungi be
detected and treated as early as possible, if the strength properties of the wood are to be maintained.
Biological tests are still the most reliable means for detecting early stages of decay.
Culturing. The early or "invisible" stages of decay can be detected by
culturing in the laboratory. Culturing is done by collecting cores in the field. Each core is placed in
a plastic straw, labeled and the ends of the straw stapled shut. The cores are brought to the
laboratory and culturing begins within 24 hours. If additional time is required before culturing, the
cores should be stored in a refrigerator or transported in chilled containers.
Once the cores arrive at the laboratory, the surface is sterilized and the core is embedded in a sterile
nutrient media. Care must be exercised to avoid contamination. The media and core are incubated
for three to four weeks at 70 to 81 degrees Fahrenheit. The cores are observed frequently for fungal
growth. Microscopic examinations are made at the end of three to four weeks to determine if the
fungi are capable of causing decay. Culturing and the recognition of decay fungi require special
equipment and trained personnel.
Insect Collection. It is usually beneficial to identify insects if an infestation
has occurred. If field identification is not possible, either collect the insects, their frass or a portion
of the wood with typical damage, and consult the cognizant PMC for assistance with positive iden-
tification.
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