Electrical properties of wood colonized by Gloeophyllum trabeum

• Relationship between electrical resistance and fungal growth is explored.
• Fungi increase the number of ions (charge carriers) in wood.
• However, the change in electrical resistance is primarily caused by changes in moisture.

This paper examines how wood decay fungi affect the electrical resistance (resistivity) of wood to determine whether an electrical resistance probe could be deployed as a remote sensor in a wall to detect wood decay. Electrical resistance measurements were taken on wood blocks exposed to Gloeophyllum trabeum in a standard soil bottle tests (AWPA E10) as a function of time. To understand how and why resistance changed with time, results were compared against resistance measurements taken in sterilized, un-inoculated wood at high moisture contents; concentrations of certain mineral ions in the wood were also measured. Results indicate that most of the changes in electrical resistance in the soil bottle test could be described by changes in moisture content alone. When the moisture effects were removed, decay fungi decreased the resistance at small amounts of weight loss but increased the resistance at high weight loss. The results presented herein help to explain the mechanism by which empirical, electrical resistance nondestructive testing devices work and also the limitations on using resistance measurements to detect wood decay.