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'.
In keeping with the theory of abiogenesis, in which living things can develop from non-living things, scientists traditionally believed that tree decay led to fungal growth. With the advent of germ theory, however, German forester Robert Hartig in the early 20th century theorized the opposite was the case, and developed a new model for tree decay: when trees are wounded, fungi infect the wounds, and the result is decayed wood. Over time, the research of Shigo and others helped to expand this theory, leading to the modern concept of tree decay: when trees are wounded, many organisms, not just fungi, infect the wood at different times and in different ways; trees respond to these infections with both chemical and physical changes; discolored and decayed wood results, but is limited by compartmentalization.
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.
By increasing understanding of how trees respond to decay, CODIT has had many applications. For example, arborists are frequently called upon to analyze 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. For another example, in the production of maple syrup holes are drilled into a tree's vascular tissues, which necessarily damages the tree. CODIT has helped farmers to better understand the effects of different tapping techniques and accordingly to change their methods to minimize damage and maximize production.
Work done by Gilman et al. at the University of Florida shows that a wound's proximity to leaf mass greatly influences compartmentalization as well as wound closure.