White Fungus on Wood

Consider using preservative-treated wood in construction to prevent fungus.

White rot fungus (Phellinus megaloporus, Poria contigua) destroys the cellulose and lignin in wood and gives wood a bleached-out appearance. Areas of infection may also exhibit a dark, black frame around the white fungus.

Occurrence

White rot fungus occurs predominantly in hardwoods but can occur in softwoods. Living trees can also suffer from varieties of white rot fungus. Wood harvested from live trees that contain a white rot fungus can be seasoned to adequately kill the fungus so the wood can still be used in industry.

Effects

White rot fungus does not cause the infected wood to crack, as other fungus infections generally do. When the decay becomes advanced, the wood begins to shrink. The wood feels spongy to the touch and loses its strength. Severe damage can occur over a 6- to 12-month period if the fungus is not treated.

Prevention/Solution

Wood subjected to a moisture content of greater than 20 percent becomes susceptible to white rot fungus and other wood rots, according to the U.S. Department of Agriculture. Preventing any leaks within a structure will help to prevent the fungus from occurring. Proper ventilation should always be installed in crawl spaces and attics to control humidity. Use preservative-treated woods when building. Borate fungicides can be used in the treatment of existing white rot fungus.

References

• Michigan State University: Wood-Damaging Fungi
• AAA American Exterminators: Wood Fungus
• Ohio State University extension Fact Sheet: Wood Rot
• Forest and Shade Tree Pathology: Wood Decay
• U.S. Department of Agriculture: Wood Decay in Houses

Resources

• University of California IPM Online: Wood Decay Fungi in Landscape Trees