Introducing the IML Resistograph

  I am happy to have purchased a new instrument that will aide in my consulting and tree assessments services called the IML Resistograph.

The resistograph is an instrument that detects decay and cavities in trees and timber. Through resistograph technology, an arborist is able to detect wood decay, stages of rot, hollow areas, cracks and ring structure. The resistograph is an ideal device for estimating tree stability and longevity. The resistograph is based on a drilling resistance measuring method developed by Frank Rinn in Heidelberg, Germany. The Resistograph in action.

The Resistograph machine uses a 19-inch long, 1/8-inch diameter drill bit. When drilled into the tree, the wood’s resistance to the drill is recorded on a strip of paper (it looks like an EKG). We usually drill three to four points at the base of the trunk and the major root flares. The tiny drilling hole closes itself up without any damage to the tree. Not every tree needs the resistograph test, but there is no substitute for this crucial test when it is indicated.

The Resistograph is used to determine the amount of decay in living trees. It is also used in root, trunk and climbing inspections. In some species, the resistograph can be used to measure tree growth diameter and bark thickness. The instrument was initially developed for the tree care industry, but is now used in multiple industries: termite and pest control, utility poles, building inspection, timber bridge inspection and playground inspection.

The resistograph is fast, accurate and reliable. Its biggest advantage is that it detects decay with virtually no tree damage. It also enables an arborist to analyze annual ring structures and to determine the growth tendency according to the width of annual rings.

The resistograph will provide you with measurable data which will determine to what extent a tree is at risk of failure. The resistograph is also a key tool for planning a landscape design. It helps homeowners, landscape architects and builders decide which trees are worth keeping and which trees may have serious problems. It is best to find out if the feature tree has any cavities before you invest in planning the rest of your landscape around it. Prevent an accident before it occurs!

Checking for decay in a Douglas fir

This Resistograph reading indicates sound wood

Lukens Tree Preservation

A certified member of the International Society of Arboriculture.

ISA Certified Member