Here’s a nightmare scenario for any homeowner: You notice a strange, orange-colored growth somewhere in the house that keeps coming back no matter how well you clean it. You open up the wall, and discover an extensive fungal infestation that is turning the solid wood of your home into a spongy disaster. It spreads incredibly fast, and unlike most molds or other fungi, it doesn’t seem to depend on an immediate source of moisture.
You’ve just encountered meruliporia incrassata, often called simply "Poria"—and it’s a huge problem. An orange-tinged fungus that develops mushroom-like bodies, Poria has been described as “the most devastating wood-decay fungus of houses that we know of” and “the most destructive fungus.”
Poria is especially destructive because of something called rhizomorphs. “Poria is unique in that it has what can be thought of as ‘long arms or tentacles,’ also known as rhizomorphs,” explains Liz Keefer, CIEC, a certified mold inspector, indoor environmental consultant, and CEO of The Mold Girl, a mold testing and inspection company based in Charleston, South Carolina. “These ‘arms’ will extend up to 10 meters in length and can travel across surfaces to find the nutrients and moisture needed to keep growing, which allows them to extend far beyond the initial infestation site. Imagine being at a restaurant surrounded by starving people with 30-foot-plus arms—and no manners to stop them from stealing.”
Unchecked, Poria can potentially do enough damage to render a house uninhabitable—and it can do that damage fast, advancing its rhizomorphs up to 10 inches a day. The good news? It can still take Poria years to do significant damage to your home (although it may go undetected for much of that time), and it’s possible to effectively get rid of it if it’s identified and treated quickly. Here’s what you need to know about this “house-eating” fungus.
Your chances of seeing Poria in your house vary greatly depending on where you live. “Poria can be found truly all over the United States,” notes Keefer, “but it is most commonly found in coastal areas, with the Southeast having the highest amount of known cases.”
A kind of “brown rot” fungus, Poria eats the cellulose in wood but leaves behind the brown lignin, leaving it dark and crumbly. The main way to know you’re dealing with Poria will be those rhizomorphs or ‘arms’—they resemble roots, and can be white or shades of brown in color. The rhizomorphs may “bleed” if broken. One challenge to identifying Poria is the fact that these ‘arms’ are typically hidden behind walls and can worm their way through tiny spaces, allowing the fungus to spread to areas of the house you might assume were safe.
Of course, once you realize you have some kind of mold eating your house, you don’t need to wait to figure out if it’s Poria or not. “All molds above normal fungal ecology levels should be considered harmful,” advises Keefer. But because of the speed of destruction that Poria is capable of, you should move a lot faster than you might with a less-invasive and less-aggressive mold or fungus.
Step one is to contact a professional mold testing company. While you might have the urge to just call a remediation company, Keefer stresses that could be a mistake. “Remediation is the term used for companies that remove mold,” she notes. “But an inspection is essential to a successful remediation, because they will find the source of the moisture which truly is the root cause.”
As Jehremy Foster, chief estimator for Precision Environmental noted to the Washington Post, you should be prepared for “a lot of demolition.” Because Poria can travel—and travel so quickly—to wood that isn’t exposed to any moisture source, treating it requires cutting away any wood that has even potentially been exposed—and rooting out the entry point of the fungus, where there is often a taproot or “root ball” that has to be removed.
The best way to deal with Poria is to never actually have to deal with it, of course. “The best way to protect your home from Poria is to be proactive in preventing excess moisture,” Keefer advises. “From proper building practices such as slanting rainwater away from the foundation of your home to monitoring relative humidity inside the home, reducing unwanted moisture is key.”
The other key to preventing any sort of damaging mold or fungus in your home is to be vigilant: Poria moves fast, so don’t ignore any common signs of fungal infestations, like:
Discoloration or stains on walls
Musty odors
Warping wood
Bubbling paint
Soft wood
In other words, being aware of the condition of your house is crucial. If you think you’ve got Poria in your house, don’t panic—but also, don’t dawdle.
