300px, The bracket fungus '' Fistulina hepatica'' is one of many that cause heart rot. In trees, heart rot is a

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

disease that causes the decay of wood at the center of the trunk and

branch A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk (botany), trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term '' ...

es. Fungi enter the tree through wounds in the bark and decay the

heartwood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin t ...

. The diseased heartwood softens, making trees structurally weaker and prone to breakage. Heart rot is a major factor in the economics of

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...

and the natural growth dynamic of many older forests. Heart rot is prevalent throughout the world affecting all

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

trees and can be very difficult to prevent. A good indication of heart rot is the presence of

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is t ...

s or fungus conks on the tree.

Biological cause

Heart rot is caused by

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

entering the trunk of the tree through wounds in the bark. These wounds are areas of the tree where bare

wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...

is exposed and usually, a result of improper

pruning Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots. The practice entails the ''targeted'' removal of diseased, damaged, dead, ...

fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. At a certain point in the combustion reaction, called the ignition ...

damage, dead

es,

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, or even

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

damage. The fungal

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s enter the exposed wounds, germinate within the wood tissues, and slowly ingest the heartwood. The infection is a very slow process and can take from months to years, depending on conditions and tree health. An average fungus will advance in the heartwood by 6–8 centimeters per year, and extensive development in the wood tissue is needed before mushrooms or conks are produced.

Impact

Heart rot fungi have both a huge economic and environmental impact. The fungi only target the nonliving wood tissue of the heartwood and do not affect the living sapwood. Initially, infected heartwood is discolored but not structurally compromised. As the fungi grow they decay more wood and the tissue becomes increasingly soft and weak. The tree can still grow around the decayed heartwood because the live wood tissue is not affected. The growth around decayed areas of heartwood creates structural weaknesses in the tree. Trees with extensive decay are more susceptible to broken branches and trunks.

Logging

Heart rot causes huge profit loss in the

industry every year due to damaged and decayed

timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...

. It is estimated that about one third of annual timber (20 billion board feet) harvest is lost due to some form of rot. Trees wounded from machinery or other falling trees are more susceptible to heart rot. It results in trees that cannot be sold due to substantial decay and introducing ideal rot conditions into younger forests that would normally not be as susceptible.

Environmental

Heart rot and other tree disease serve as factors of environmental change. This is magnified in areas that are not prone to large-scale dynamic disturbances like wildfires or are dominated by

old-growth An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological feature ...

timber. In older-growth forests, trees are unable to combat heart rot effectively because they grow at a much slower pace. Extensive rot causes these trees to be more susceptible to high winds and trunk fracture. As the old growth dies out, it allows new growth to take its place, altering the dynamic of the environment. Decaying trees and

tree hollow A tree hollow or tree hole is a semi-enclosed cavity which has naturally formed in the trunk or branch of a tree. They are found mainly in old trees, whether living or not. Hollows form in many species of trees, and are a prominent feature of nat ...

s also provide shelter to animals as well as

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s. Through this process of dynamic change, heart rot contributes to biologically diverse

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

Prevention and control

The prevention of heart rot can be a very difficult task, but there are effective measures to minimize damage. These methods include facilitating healthy growth, minimizing wounds, and proper pruning of branches. A healthy tree naturally combats heart rot through a process called compartmentalization. The tree grows around the decayed wood tissue and prevents the fungus from spreading to a larger area of the trunk. Providing a tree with the necessary nutrients, water, and growing conditions will promote healthy growth and minimize rot. The bark is the tree's main defense against disease; reducing the amount of large wounds and bare wood, especially in older trees, helps prevent rot.

Pruning techniques

Pruning Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots. The practice entails the ''targeted'' removal of diseased, damaged, dead, ...

focuses on removing dead or diseased branches with minimal damage done to the tree. Branches connect to the trunk and grow from the

branch collar A branch collar is the "shoulder" between the branch and trunk of woody plants; the inflammation formed at the base of the branch is caused by annually overlapping trunk tissue. The shape of the branch collar is due to two separate growth pattern ...

. While the branch itself may be dead, the branch collar is still healthy and resistant to disease. It is from the branch collar that a new limb will generate and grow, so it is important not to damage it while pruning. Make clean cuts at the base of the branch adjacent to the branch collar. Small branch stubs (larger than three inches) will inhibit the growth process and provide fungi with ideal growth environments.^ Hickman, G.W.. "Wood Decay Fungi in Landscape Trees Management Guidelines--UC IPM." UC Statewide Integrated Pest Management Program. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74109.html#IDENTIFICATION (accessed January 25, 2010).

Examples

The following are some trees susceptible to heart rot: *

Alder Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...

Aspen trunk rot Aspen trunk rot is a fungal disease that causes stem decay heart rot of living aspen trees. The pathogen that causes this disease is the fungus ''Phellinus tremulae''. Most of the symptoms of this disease are internal, with the only external signs ...

Spirostachys africana ''Spirostachys africana'' is a medium-sized (about tall) deciduous tree with a straight, clear trunk, occurring in the warmer parts of Southern Africa. Its wood is known as tamboti, tambotie, tambootie or tambuti. It prefers growing in single-s ...

References

External links

{{Portal, Trees
Picture of a tree with heart rotThe heart rot fungus
Fungal tree pathogens and diseases