ID-253 University of Kentucky College of Agriculture, Food and Environment Species Failure Profile for Trees Cooperative Extension Service Common to the Ohio River Valley William M. Fountain, University of Kentucky Horticulture; Julie Beale, University of Kentucky Plant Pathology; Stacey Borden, University of Kentucky Arborist; Steve Foltz, Cincinnati Zoological and Botanical Garden; Lindsey Purcell, Purdue University; and David Vandergriff, University of Tennessee ree failures, especially in urban where the branch is attached to the about your tree, the prudent thing to and recreational areas, can result trunk or larger branch and where the do is to have your tree(s) inspected by inT harm to human life and property. foliage is attached. Branch failures often a qualified arborist. Arborists with the It is important, however, to recognize occur at the branch union (bifurcation, International Society of Arboriculture that the environmental and sociological branch crotch) where the branch joins (ISA) Certified Arborist® credential or benefits provided by trees significantly the trunk. Branches with a tight branch the Tree Risk Assessment Qualifica- outweigh the limited risks presented by union (V-shaped branch union) fre- tion® (TRAQ) are trained to detect and trees. Defects and species profiles that quently have included bark, making the mitigate defects in trees. increase the potential for failure often branch union weak. Lateral branches Note: This guide is intended as an aid can be observed or detected; many de- that are vertical are called co-dominant to identifying genetically influenced fects are associated with certain species, leaders. These branches grow longer and characteristics that may lead to failure referred to as the species failure profile. increase in weight more rapidly than of trees or parts of trees: site character- When trees fail, they fail in one of more horizontal branches, resulting in istics (i.e. soil volume, aspect, percent three general patterns: whole tree failure, greater loads on the branch union. slope, etc.); environmental characteris- failure at the trunk, or branch failure. Trees species are genetically variable tics (i.e. wind speed, duration, loading; Whole tree failure frequently occurs in their ability to produce strong parts drought; temperature, moisture, etc.); because of confined roots; cut roots and remain structurally sound. These and loss of strength caused by other resulting from activities such as trench- variabilities involve wood strength, factors (i.e. diseases, insect, animal ing; decay or death of roots; or soil failure susceptibility to fungal wood decay or- damage). Failures can and will occur where healthy roots lose the ability to ganisms, and the likelihood of a species for reasons other than those listed. The anchor the tree and pull out of the soil. to produce structurally branch unions. time of failure cannot be predicted. Trunk failures frequently occur at The following table details species Trees are biological organisms that the point where decay organisms have failure profiles associated with species accumulate defects throughout their weakened the trunk. Certain species are common to the Ohio River Valley. Not lives. Not all of these defects can be more prone to wood decay organisms all members of a species will have all of observed or detected, even with the than others. Wind hitting a tree’s crown the defects associated with the species. most advanced equipment available. transfers force to the trunk. Without Many only result when the tree is grow- defects in the trunk, breakage will usu- ing in a less than ideal location. ally occur about half way between the Property owners have a duty and soil and the bottom of the canopy. obligation to inspect the trees on their Address correspondence to: Like trunk failures, branch failures property to ensure that they do not Bill Fountain ([email protected]) occur at defects or half way between have obvious defects. If you are unsure Glossary attachment–the point where a branch arises from the trunk (stem) butt rot–decay of the lower trunk, trunk flare, or buttress roots. or another branch, also known as branch attachment, bifurca- buttress root–roots at the trunk base that help support the tree tion, or crotch. and equalize mechanical stress. borer–an insect that feeds in xylem tissue. Flatheaded borers canker–localized diseased area on stems, roots, or branches that is (Agrilus spp., Chrysobothris spp.) are beetle larvae that usually often shrunken and discolored. feed in the most recent annual growth ring and can result in CODIT–acronym for Compartmentalization of Decay in Trees. death of the branch; roundheaded borers (Acanthocinus spp., codominant leader–forked branches that are nearly the same Oberea spp., Saperda spp., Synanthedon spp.) are moth or beetle size in diameter arising from a common junction. These branch larvae that usually feed throughout the xylem often resulting in unions often have a V-shaped union (as opposed to a U-shaped branch failure. union) and often have included bark. Cooperative Extension Service | Agriculture and Natural Resources | Family and Consumer Sciences | 4-H Youth Development | Community and Economic Development compartmentalization–natural defense process in woody plants sapwood rot–decay located in the sapwood. Bark and/or cam- by which chemical and physical boundaries are created that bium may be damaged or dead. A common sign is the presence act to limit the spread of diseases and decay organisms. Often of numerous, small fruiting bodies on the bark. referred to as CODIT. soil failure–the inability of soil to provide sufficient resistance to dynamic loading–force that is created on a branch or other plant prevent roots from sliding out of the soil resulting in whole part that changes with time and motion (i.e. wind, climbers, rig- tree failure. This occurs more frequently when soil is saturated. ging operations, etc.). Contrast with static loading. Contrast with root failure. girdling root–root that encircles all or part of a tree trunk or other species failure profile–known types of failure associated with a roots, constricting vascular tissue and inhibiting secondary species. growth and the movement of water and photosynthates. static loading–constant load exerted by a mass due to its weight heartwood rot–any of several types of fungal decay of tree (i.e. snow, ice, epiphytes, gravity, etc.). Contrast with dynamic heartwood, often beginning with infected wounds in the living loading. portions of wood tissue. Also called heart rot. sudden branch drop–unexpected failure of large branches, usu- included bark–bark that has become imbedded in the branch ally on hot, calm, days and evenings. Failures are generally at union (bifurcation, crotch) between the branch and trunk or the union between a mature, over-extended, horizontal branch between codominant stems. Included bark is associated with and trunk. This type of failure is rare but has been more closely failure of branches and codominant stems. associated with some genera (i.e. ash, beech, buckeye, chestnut, internal decay–wood (xylem) that is undergoing decomposition elm, Japanese pagodatree, maple, oak, pine, poplar, sycamore, by fungi or bacteria. sweetgum, tree of heaven, tulip poplar, willow) and inappropri- load–see dynamic loading, static loading. ate water relations. It is associated with extreme drought fol- mechanical damage–injury by mowing equipment, construction lowed by the breaking of the drought. It is thought to occur as a equipment, animals, etc., with the potential for the introduc- result of wood drying and shrinking (cracking) during drought tion of pathogens (especially fungi) with the ability to colonize followed by rehydration and the resulting weight increase. It is wounds, resulting in internal decay. often associated with other defects (wetwood, included bark, risk–the likelihood of an event occurring (tree or tree part falling etc.). It is difficult to impossible to identify branches with the and striking a target) compounded with the consequences of potential to fail. this event occurring. target–people, property, or activities that could be injured, dam- risk assessment–the systematic process used to identify, ana- aged, or disrupted by a tree failure. lyze, and evaluate the likelihood of tree failure and associated whole tree failure–failure of an entire tree at or near the soil line consequences. resulting from uprooting (soil failure), root decay (root failure), root failure–breaking of the roots, usually from internal decay or decay of the lower portion of the trunk. resulting in whole tree failure. Contrast with soil failure. Table 1. Species failure profiles for trees common to the Ohio River Valley Observed Frequency of Species Common Name Failure Defects Abies concolor white fir Low Codominant leaders, whole tree failure due to cankers, internal decay, butt & root rot Abies nordmanniana Nordmann fir Low Codominant leaders, whole tree failure due to cankers, internal decay, butt & root rot Acer spp. maples Maples often have codominant leaders (due to opposite leaf ar- rangement) often with included bark, surface roots (potential for decay resulting from mechanical damage), girdling roots, sudden branch drop, cankers. Most species are poor compartmentalizers, verticillium wilt resulting in death and wood decay. Acer buergerianum trident maple Low Potential for codominant leaders with included bark. Smaller size reduces risk of harm. Acer campestre hedge maple Low Potential for