Glossary of Arboriculture Terms


Resistograph

A Resistograph is a test instrument used to detect decay within trees.  The device is a small drill bit that penetrates the trunk of the tree while recording the torque on the bit.  When torque is measured high the wood is solid conversely when torque is low the wood is decaying or even absent. When a tree trunk is tested in multiple locations a picture can be made of the tree’s density.  Results are used to determine the amount of decay in a tested cross-section and used to calculate the amount of strength lost because of that decay.