"The House Eating Fungus"
The following is some information on this structure damaging
macro-fungi to date (May 1, 2001).
the last 2 decades Meruliporia incrassata, sp., an orange colored
mushroom shaped macro fungus, with the appearance of pancake batter,
has shown up recently in homes from San Diego to northern California.
However, poria incrassata, the water-conducting fungus occurs
mainly in the southern states, it can be found anywhere. In the
past, reports of poria was confined mainly to the Gulf states
Miss, Al, Tx, etc.
"It's a rare fungus, but it's as common here as anywhere
in the world," said UC Riverside plant pathology professor
John Menge. "It's also the most devastating wood-decaying
fungus of houses that we know of".
Poria is one of many wood decay fungi that feeds on dead wood.
It sounds like science fiction and looks like it too, but poria,
like all decay fungi, is an organism that needs moisture to
break down and utilize wood as a food source, according to forest
product experts at UC Berkeley. But unlike other wood-decaying
fungi, which tend to destroy only a six inch area around a plumbing
leak or wet window sill, poria has the capacity to begin in wet
soil as opposed to just damp soil.
Experts say this water-conducting fungi differs from most other
wood decay fungi in several respects: Large, semi-tough water-conducting
roots called rhizomorphs are formed which transport water by capillary
action from a constant source (usually damp or wet soil) to dry
wood in a building, wetting it sufficiently to support decay.
As decay proceeds, water is conducted to dry wood adjacent to
that already colonized fungi. In this manner, as long as the supply
of water is available, water-conducting fungi can colonize and
decay the wood to the entire structure. "In other words,
because fungus does not have teeth to help it eat, it has to spit
on the wood. And the enzyme it secretes turns the wood to mush.
Any piece of wood exposed to this fungus is destroyed" says
poria expert Glenn Sigmon.
We used to think poria would usually start under a newly installed patio, with
new landscaping or with a new room addition, and can travel far
from its original water source. But that is not always the case.
Wayne Wilcox, a UC Berkeley forestry
professor, has found a similarity among houses with poria and
the fact that major landscaping was done within 2 years of poria's
onset. He speculates that the soil dumped on these suburban lawns
originated in various forests around the world, where poria occurs
naturally and helps in the process of decomposition, and he feels
poria may have come along for the ride.
Donna Kingwell, a spokeswoman for the California state's Structural
Pest Control Board, said "the agency is keenly aware of the
potent problems of poria, especially in the southern part of
First reports of poria incrassata destruction surfaced in 1913
in the southeastern United States, where forest products were
the suspected origin of the fungus-abound. There is no record
of the first reported case of poria in California, according to
Wayne Wilcox, a UC Berkeley forestry professor, but scientists
discovered the telltale spores on three coastal redwoods in 1924.
Infestations of poria are rare. Only 15 cases were reported state
wide by 1968, according to a U.S. Department of Agriculture study.
"When poria does invade a house, it's almost always catastrophic",
said Mississippi State University wood technology professor Terry
Amburgey. "The fungus will infiltrate a foundation, wood
or concrete, and pretty soon the entire house goes".
Poria has an appetite not only for common construction woods
such as oak and pine, but for cedar, redwood, cypress and juniper
that are naturally decay-resistant. In addition to attacking most
woods classed as naturally decay resistant, laboratory tests show
that poria is resistant to many fungicides containing copper.
The practical significance of this tolerance is uncertain, but
no failures of wood treated with copper fungicides have been reported
in buildings to date.
When poria attacks a building, spectacular damage often results
once well established it can destroy large areas of floors and
walls every year or so. Fortunately, control is relatively simple,
i.e. the permanent elimination of the water source. Although poria
is relatively rare, the rapid and extensive damage it can cause
makes it desirable to understand the conditions leading to the
attract, the signs indicating an attack is in progress, and methods
of prevention and control of an attack.
Control and Remediation
"The bad news about poria is that it's hidden and it spreads
fast, but once you find it, it can be controlled," said Wayne
Earlier control recommendations called for the removal of decayed
wood and all sound wood within 2 feet of obvious visible growth
on the assumption that poria, once established, can decay wood
with metabolic water as the sole source of moisture.
Poria Incrassata is more sensitive to higher temperatures than
most decaying fungi and is killed in moist wood at temperatures
only moderately above "air-temperature maxima". This
explains why poria occurs in the more protected parts of structure
and not in wood exposed to full sun. In other words, poria is extremely sensitive
to drying. In naturally infected wood, it can survive only 32
days of air drying. In laboratory tests, all artificial infections
were dead in 1 day at 10% RH (relative humidity), 5 days at 65%,
and 10 days at 90%. Sensitivity to drying, in conjunction with
the need for conducted-water, forms the basis for the presently
recommended simplified control and remediation measures.
Call the poria experts at Aqua Restoration at 1-800-201-8103
for an estimate on the removal and to keep it from coming back.
Below are a couple of pictures of a project before and after