Which trees are most susceptible to decay?

Which trees are most susceptible to decay?

Some trees are more susceptible to decay than others, and it’s essential to identify them to prevent potential hazards. In this article, we will explore which trees are the most susceptible to decay and what factors contribute to their vulnerability.

Factors Contributing to Tree Decay

Before we delve into which trees are most susceptible to decay, it’s crucial to understand the factors that contribute to tree decay. There are three primary factors:

  1. Fungi: Fungi are the primary cause of decay in trees. They feed on the wood and break down its structure, causing the tree to lose its strength and stability.
  2. Moisture: Trees require moisture to survive, but excessive moisture can lead to decay. If a tree is constantly exposed to damp conditions, it becomes more susceptible to fungal decay.
  3. Damage: Trees that have been damaged by storms, pests, or other factors are more susceptible to decay. The damage creates openings for fungi to enter the tree and start the decay process.
Which Trees Are Most Susceptible to Decay?
  1. Elm Trees: Elm trees are highly susceptible to Dutch elm disease, which is caused by a fungus spread by bark beetles. The disease attacks the tree’s vascular system, causing it to wilt and die.
  2. Oak Trees: Oak trees are susceptible to a variety of fungal diseases, including oak wilt and anthracnose. Oak wilt is caused by a fungus that disrupts the tree’s water-conducting system, while anthracnose attacks the tree’s leaves and twigs.
  3. Maple Trees: Maple trees are susceptible to a variety of fungal diseases, including verticillium wilt and tar spot. Verticillium wilt attacks the tree’s vascular system, while tar spot causes black spots on the tree’s leaves.
  4. Ash Trees: Ash trees are susceptible to emerald ash borer, a beetle that feeds on the tree’s inner bark and disrupts its ability to transport nutrients and water.
  5. Pine Trees: Pine trees are susceptible to a variety of fungal diseases, including white pine blister rust and pine wilt. White pine blister rust attacks the tree’s needles and shoots, while pine wilt causes the tree’s needles to turn brown and die.
Preventing Tree Decay

Preventing tree decay requires regular inspections and maintenance. A qualified arborist can identify potential hazards and recommend solutions to prevent further decay. Some preventative measures include:

  1. Pruning: Pruning removes dead or diseased branches and improves the tree’s structure, reducing the risk of damage from storms.
  2. Fertilization: Fertilization provides essential nutrients to the tree, improving its overall health and ability to resist decay.
  3. Pest Management: Pest management can prevent infestations of pests like emerald ash borer and bark beetles.
  4. Drainage: Proper drainage prevents excessive moisture from accumulating around the tree’s roots, reducing the risk of fungal decay.

In conclusion, understanding which trees are most susceptible to decay is crucial in maintaining a safe and healthy environment. By identifying potential hazards and taking preventative measures, homeowners and gardeners can ensure their trees remain healthy and vibrant for years to come.

Facts on Tree Decay
  1. Decay in trees is caused by fungi that consume the wood fibers.
  2. Most trees have some decay fungi in their tissues, but healthy trees are able to resist them.
  3. Decay fungi can be spread through contaminated pruning tools or by insects that bore into the tree.
  4. Signs of decay in a tree can include cavities, cracks, or soft, spongy wood.
  5. Some trees are more susceptible to decay than others, such as those with weak wood or trees that have been injured or stressed.
  6. Decay can weaken a tree’s structure and make it more susceptible to falling or breaking in a storm.
  7. Preventative measures such as proper pruning, avoiding injury to the tree, and maintaining healthy soil conditions can help reduce the risk of decay.
  8. Some species of trees, such as oak and elm, are particularly susceptible to certain types of decay fungi.
Decay ranking for commonly planted species:


Tree SpeciesSusceptibility to Decay
Pinus radiata (Monterey Pine)High
Platanus x acerifolia (London Plane)Moderate
Robinia pseudoacacia (Black Locust)Moderate
Ailanthus altissima (Tree of Heaven)Moderate
Ulmus pumila (Siberian Elm)Moderate
Betula pendula (European White Birch)Moderate
Fraxinus americana (White Ash)Moderate
Populus nigra (Black Poplar)Moderate
Quercus cerris (Turkey Oak)Moderate
Salix babylonica (Weeping Willow)Moderate
Acer platanoides (Norway Maple)Low
Ginkgo biloba (Maidenhair Tree)Low
Koelreuteria paniculata (Golden Rain Tree)Low
Magnolia grandiflora (Southern Magnolia)Low
Catalpa bignonioides (Southern Catalpa)Low
Albizia julibrissin (Silk Tree)Low
Cercis canadensis (Eastern Redbud)Low
Jacaranda mimosifolia (Jacaranda)Low
Lagerstroemia indica (Crape Myrtle)Low
Prunus serrulata (Japanese Cherry)Low
Sophora japonica (Japanese Pagoda Tree)Low
Tilia cordata (Littleleaf Linden)Low
Zelkova serrata (Japanese Zelkova)Low
Links for further reading
  1. Tree Decay and Risk Management: https://www.fs.fed.us/rm/pubs_other/rmrs_2012_smith_d001.pdf
  2. How to Recognize and Prevent Tree Decay: https://www.treesaregood.org/portals/0/docs/treecare/Tree-Decay.pdf
  3. Tree Decay and Urban Forests: https://www.researchgate.net/publication/260631465_Tree_Decay_and_Urban_Forests_Availability_and_Utility_of_Decay_Assessment_Methods
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