Poria: The Uninvited Guest
Uncommon Fungus Finds Homes the Perfect Hosts
Turns Wood to Mush
A fungus is sprouting up around Southern California, snaking around
stucco and brick to get to its daily meal--the wood in and around
When the feast is over, once-solid walls and floors are left mushy
enough to put a pinky finger through, and once-secure property
owners are left scrambling to come up with the thousands of dollars
needed to repair the damage.
In the last two decades, Meruliaporia incrassata--an orange-colored,
mushroom-shaped fungus--has shown up with more frequency in houses
from San Diego to Northern California. And because most homeowners,
pest control inspectors and contractors are unfamiliar with the
unusual growth commonly called poria, the fungus spreads untreated
and unchecked through houses big and small, an equal-opportunity
"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-decay fungus of houses that we
"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 Wilcox, a UC
Berkeley forestry professor.
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 decay 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--usually under a newly installed
patio, new landscaping or a room addition--then travel to dry wood
by pumping water through a root-like system. Far from its original
water source, the fungus continues to feed on the new supply of
Donna Kingwell, a spokeswoman for the state's Structural Pest
Control Board, said the agency "is keenly aware of the potent
problems of poria, especially in the southern part of the state."
La Canada homeowner Laurie Rodli is also keenly aware of poria's
The mother of two and her husband, Eric, moved into their
50-year-old remodeled home early in 1994. Three months later, she
noticed stale-smelling, fuzzy growths cropping up in some unpacked
boxes in the dining room.
When she opened the boxes, she discovered their interiors were
covered with smelly, orange flowerets and they were stuck to the floor.
She emptied the boxes and threw them away. But the following summer,
Rodli tried to open the drawers of a spare dresser in her son Mark's
closet, but they were glued shut. Pulling the dresser away from the
wall, she discovered that the back of the bureau had been eaten away
and the closet wall and floor were warping.
A contractor cut out the floor of the closet and a portion of the
bedroom to discover that the fungus had rotted the subfloor.
"We couldn't find a leak, even under the sink and toilet. What was
causing this?" Rodli wondered.
Like the voracious plant in "Little Shop of Horrors," the fungus
showed up again months later--even after the affected areas had been
treated--this time warping the dining room floors and walls.
"We just thought we had some new dry rot on the dining room French
doors," Rodli said. "Unfortunately, we let it go."
Last July, she called a new contractor. As he inspected the house,
his foot fell through the living room floor. He ripped up the
dining-room and living-room floorboards, where widespread damage was
revealed: The fungus had crept through half the house, eating away
the subfloors and even parts of the fireplace.
In November, Luis De La Cruz, a Van Nuys pest control specialist
and, according to UC Berkeley's Wilcox, one of the few inspectors in
California who has learned to recognize the fungus, examined the
property and broke the news to the Rodlis: The mysterious fungus
gobbling up their house was poria, and eradication would involve
opening up walls, tearing up floorboards and demolishing the back
They would also have to ventilate the foundation of the house,
install an irrigation system in the backyard and repair the interior
The price tag: at least $60,000, exclusive of landscaping, her
"I cried off and on for two days while my kids were at school,"
Rodli said. "The chaos was unbelievable. I'd just burst into tears
every time I looked around."
De La Cruz has experienced this reaction all too often in the last
"Poria is a monster that no one wants to hear about," De La Cruz
said. "We can look at a house during an inspection and everything's
fine. Six months later, it has wreaked havoc. It's scary."
The pest control inspector saw his first case of the fungus on the
lattice work of a house in 1969. It dried up and quickly
disappeared, so he didn't think about it again until 1979, when he
was asked by a Los Angeles Department of Building and Safety
supervisor to check out an Encino home infested with an unusual
UC Berkeley's Wilcox helped De La Cruz correctly identify the fungus
and suggested ways to eradicate it.
By 1992, after successfully identifying and treating a number of
cases of poria around Southern California, De La Cruz had
established a reputation as a poria expert, Wilcox said.
First reports of Meruliaporia incrassata destruction surfaced in
1913 in the southeastern United States, where forest products--the
suspected origin of the fungus--abound.
There is no record of the first reported case of poria in
California, according to Wilcox, but scientists discovered the
telltale spores on three coastal redwoods in 1924.
Infestations of poria are rare--only 15 cases were reported
statewide by 1968, according to a U.S. Department of Agriculture
Poria experts believe that more recent increases in California can
be traced to new building standards established after the oil crisis
in the late 1970s. To conserve energy, houses have been built close
to the ground, where the fungus has easy contact with wood. Newer
homes also tend to have poor ventilation, Wilcox said, allowing
poria to thrive.
Because neither the state nor Los Angeles requires an inspection for
poria when homes are bought or sold, or when they are under
construction, no state or city agency keeps accurate track of cases,
according to the state Structural Pest Control Board and the L.A.
Department of Building and Safety.
However, De La Cruz said, in the last year alone, he has identified
about 80 cases in California, and UC Riverside's Menge said he
expects a bad infestation this fall because of last winter's heavy
rains. "It takes awhile to get started after the rains."
When poria does invade a house, it's almost always catastrophic,
said Mississippi State University wood technology professor Terry
"The fungus will infiltrate a foundation--wood or concrete--and
pretty soon the entire house goes," Amburgey said.
That was nearly the case at a 22-unit, beachfront Malibu condominium
complex, whose wood piles supporting the building were destroyed by
Los Angeles forensic architect Mark Savel discovered the huge fungal
infestation in the building's foundation last year, and quickly
realized it had spread throughout the complex.
Despite the obvious source of water near the Malibu building, the
fungus was not fed by the ocean, but by a subterranean septic
system. Foundation repairs cost $600,000.
The homeowners association members, whose insurance policies did not
cover fungus infestation, were forced to pay the expenses out of
One of the most serious roadblocks to eradicating poria is
convincing homeowners that a patch job will not cure the problem.
When they hear about tearing open walls and digging up foundations,
they seek another opinion, often from termite inspectors and
contractors who have no experience in treating the fungus.
"I feel there are times when I'm the messenger who will be shot,"
Savel said. "Homeowners reject reports about a degraded floor joist
until they see the wood crumbling in my hands. They want to make a
quick repair. All I can do is explain the alternative, which is
Fears of plummeting property values, coupled with the shame attached
to publicly acknowledging a fungal infestation, often result in
homeowners rejecting experts' advice altogether, even when the house
is in danger of collapse.
De La Cruz fears that will soon be the case with a large two-story
Northridge house he recently inspected.
The owner rejected his poria diagnosis--and the estimated $100,000
cost to eradicate it--and sought three other opinions until the
owner finally was told what he wanted to hear: The tennis-ball-sized
growths sprouting up like toadstools around the window sills,
door jambs and supporting columns were the result of badly aimed
According to De La Cruz, the poria was so widespread that anything
short of its immediate eradication may soon result in the collapse
of the home.
The Northridge resident, like several other homeowners contacted for
this story, refused to be interviewed.
Homeowners who decide to eradicate the fungus are hit with a one-two
punch: First they're told that the repairs will cost thousands of
dollars, and then that their insurance policies may not cover it.
Since poria, a hidden problem that develops over time, is discovered
long after the destruction has begun, most claims are rejected.
Joe Howard, a Sherman Oaks resident, fought his insurance company
Howard discovered the telltale orange ooze growing at the
intersection of the wall and floor in his daughter's bedroom 2 1/2
"I thought it was cat vomit," he said. "After we stripped the walls
away, we found the stuff everywhere. It's like a parasite or a
vampire attached to the house."
With an estimated cleanup cost of $15,000, Howard called his State
Farm Insurance agency, which turned down his claim.
After the Consumer Services Division of the California Department of
Insurance refused to act on his behalf, Howard told State Farm he
intended to pursue his claim further. The insurance company agreed
to an arbitration hearing to settle the matter.
Howard won his case after proving to the judge that the poria
infestation caused the collapse of his home, a clause included in
his homeowners policy.
"I had to bring in a pamphlet put out by the U.S. Department of
Housing and Urban Development that explains what poria is, just
so the judge would understand the severity of it," Howard said.
State Farm spokesman Phil Supple said the insurance company still
covers structures that collapse due to hidden decay, but added that
the definition of "collapse" is decided on a case-by-case basis.
A claim for Rodli's repairs, which the family initially financed
themselves, was settled with 20th Century Insurance Co. in May. The
checks, which covered about half the costs, arrived six months after
the work had begun.
"We had to eat, sleep and breathe this mess for so long," Rodli
said. "Our kids were asking if there would be any money left over
for their college. When I looked at my house literally crumbling, I
The Rodlis' new homeowners policy specifically excludes future
coverage for loss caused by mold, rot and fungus.
A 20th Century spokesman declined to discuss the case, but he did
confirm that most insurance companies are unwilling to cover damage
that is not the result of a sudden catastrophe, such as fire or
burst water pipes.
"If poria becomes a widespread problem, insurance companies,
trying to meet the needs of customers, may have to change," said Ric
Hill, vice president of corporate relations at 20th Century
Insurance Co. "But the process won't change overnight."
Rodli, meanwhile, is enjoying her newly landscaped backyard, and is
trying to put the five-year episode behind her.
"Now that it's over, I can breathe easier," Rodli said. "I hope that
no one I know ever has to go through this."
Managing the Fungus
People with mold and mildew allergies are advised to avoid contact
with the material during cleanup. Inhalation of spores can lead to
inflammatory reactions, such as chronic sinusitis and bronchitis.
Signs of Infestation
* Separation of baseboards from the floor.
* White threadlike membranes forming fan shapes under wallpaper or
* Swelling and crumbling of plaster or drywall.
* Mushroom-shaped fruit bodies on rotten wood around window sills,
cupboards or the underside of flooring.
* Irregular vine-like roots branching in the soil and extending to
foundations, framing or the subflooring.
Methods of Control
* Locate and remove the fungus' source of water, usually near the
point of greatest decay, and repair any plumbing leaks.
* Cut the roots, or rhizomorphs, and scrape fungus growths from the
* Remove contaminated soil from the property.
* Dry out all affected areas, from floor joists to ceilings.
* Replace decayed wood with pressure-treated lumber.
* Once the fungus is eradicated from a home, the property should be
inspected by a poria expert once a year.
UC Berkeley's Wayne Wilcox and pest control specialist Luis De La
Cruz give periodic workshops for general contractors and pest
control inspectors on the identification and treatment of
For information, call the state Structural
Pest Control Board, (916) 263-2540.
The UC Forest Products Laboratory in Berkeley has also set up a
telephone number where people may leave their addresses to get
information mailed to them about poria: (510) 215-4261.
Sources: U.S. Department of Agriculture, the U.S. Forest Service,
the U.S. Department of Housing and Urban Development, and the
California Department of Health Services
Los Angeles Times - Los Angeles, Calif.
Date:Jul 30, 1998
|De La Cruz|
Wood Preservation Services
14547 Titus St. #211
Van Nuys, CA 91402
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Wednesday, January 29, 2020