cooperative extension advisor on wood durability at the
University of California Forest Products Laboratory in
Richmond, Calif., responds: Yes, there are laboratories
that can identify fungi based on culturing samples taken from
decayed wood on site, but the process can be time consuming and
the service may not be free. Two laboratories that provide the
service are the Center for Forest Mycology Research at the U.S.
Forest Products Lab in Madison, Wisc. (contact Harold Burdsall,
608/231-9234), and the Department of Forest Products at Oregon
State University in Corvallis (contact Jeffrey Morrell,
541/737-4222). Should you decide to pursue this, call Dr.
Burdsall or Professor Morrell for specifics on how to collect
and prepare the sample for shipment.
Because the laboratory procedure can take a month or longer
to complete, it may be safer for you to diagnose it in the
field. Meruliporia incrassata (the recently changed
scientific name for poria) can be identified by the presence of
the water-conducting rootlike tube called a rhizomorph and by
the appearance of the fruiting body and the dark colored spores
it produces. The rhizomorph looks like a barkless root and
smells like a mushroom if broken open.
Figure 1.The rhizomorph of the poria fungus is a
Since the required repair scenario for homes damaged by a
water-conducting decay fungus is different from that for
non-water-conducting decay fungi, it is critical to determine
whether or not the damage has been caused by poria. For
non-water-conducting decay fungi, you have to find the source
of liquid water that is making the wood wet enough for decay to
occur, and stop it. With poria, the rhizomorphs supply the
water, and therefore they all need to be found and severed.
Severing the rhizomorphs will eliminate the water source and
kill the fungus.
Finding and cutting the rhizomorphs can be difficult,
particularly with slab-on-grade construction. The rhizomorphs
can move through some very tight openings, such as plumbing
penetrations and cold joints between two concrete pours. To
prevent poria from infecting the house again, you need to
change the construction detail that allowed the rhizomorph to
get to the house without drying out (for example, by providing
an adequate air gap between wood and soil).
Figure 2.One identifier of Meruliporia
incrassata is its fruiting body.
Because of the importance of finding the rhizomorphs, you
should consider enlisting the help of a pest control operator
with poria experience. The University of California Forest
Products Laboratory has prepared a poria package with a summary
of many of the published documents on Meruliporia
incrassata. To request this package, call 510/215-4261 and
leave your name and address after the recorded