Detection of Wood Decay in Blue Gum and Elm: An Evaluation of The Resistograph ® and the Portable Drill

Abstract

Decay and soundwood assessments made with the Resistograph ® and the portable drill were compared with laboratory measurements of wood density. Sixteen Tasmanian blue gum ( Eucalyptus globulus ) and 5 Scotch elm ( Ulmus glabra ) were evaluated in the field, cut, sectioned along Resistograph and drill test paths, and measured for density. Resistograph measurements of soundwood depth agreed closely with density measurements in 85.5% of all cases for blue gum and 100% of all cases for elm. Portable drill measurements agreed closely with density measurements in 73% of cases for blue gum and 81% for elm. Drill evaluations varied considerably among operators. For both species, the Resistograph provided a higher level of consistency and reliability than the portable drill. For either method, familiarity with wood resistance patterns of the test species is critical for an accurate interpretation of decay presence or absence.