Types of decay in trees.

What is Decay ?

Compartmentalization Of Decay In Trees (CODIT), also known as Compartmentalization Of Disease In Trees by some, is a concept created by Dr. Alex Shigo after years of studying tree decay patterns. Though disputed upon its introduction in the late 1970s, the concept is now widely accepted by modern arboriculture and is referenced widely in publications including Shigo’s ‘Modern Arboriculture’ and ‘A New Tree Biology’.



According to CODIT, when a tree is wounded cells undergo changes to form “walls” around the wound, slowing or preventing the spread of disease and decay to the rest of the tree.

Decay is put into classifications based on whether it is growing above or below ground. When the roots or central area of a trees root plate are decaying this is classed as Below Ground Decay. On establishment within the central area it can travel into the base of the stem in an upward direction, this type of decay is termed butt or root rot. The fruiting bodies (Mushroom type growth) of these types of rot can be found between buttresses of trees or on the ground above affected roots.

When the branches and stems of trees are infected, usually after dieback from other causes or injury to the tree, this is termed above ground and ‘top rot’ can travel downwards maybe meeting the upward moving rot from below ground decays. The fruiting bodies form on branches and stems of areas affected.




There is a further breakdown of the classification dependant on the type of rot produced from a particular fungi, these are;

White Rots -These can be further broken down into; Simultaneous rot and also Selective delignification.

White rot fungi possess both cellulolytic and lignin degrading enzymes and these fungi therefore have the potential to degrade the entirety of the wood structure under the correct environmental conditions.




Brown Rots

The wood decayed by brown rot fungi is typically brown and crumbly and it is degraded via both non-enzymatic and enzymatic systems. A series of celluloytic enzymes are employed in the degradation process by brown rot fungi, but no lignin degrading enzymes are typically involved.




Soft rot fungi typically attack higher moisture, and lower lignin content wood and can create unique cavities in the wood cell wall.




By increasing understanding of how trees respond to decay, CODIT has had many applications. For example, we as arborists are frequently called upon to analyse the danger posed to people or property by a damaged or decaying tree. By knowing how decay is likely to spread, such hazard tree analyses may be more accurate, thereby preventing unnecessary tree removal, property damage, or injury.

If you have suspected decay in any of your trees then we would be pleased to inspect them for you, please call us on 0800 3287988 to arrange a visit by one of our surveyors.


Mark Kirk ND Horticulture. FdSc Arboriculture 
Contract Manager

Email: mark.kirk@beechwoodtrees.co.uk