Green Tips: Tree IDing (Diseased, Dead, or Dormant?)

Green Tips | October 8, 2020

Most of the trees that we see are deciduous trees, which make up more than 70% of New York State’s forests. These are the kind of trees that shed their leaves in autumn and have bare branches throughout the winter. In the spring, the leaves of these trees regrow. However, as the leaves start to fall and trees become bare, it may be difficult to tell whether deciduous trees are diseased, dead, or going dormant. It is important to be able to identify dead or diseased trees because they can pose serious safety risks such as falling down, attracting pests, and spreading infections to nearby trees. As the leaves start falling, this week’s Green Tip will help you identify trees that may need attention, and bring awareness to common tree diseases. 

Diseased, Dead, or Dormant?

When a tree is bare, it may be hard to tell whether it is diseased, dead, or dormant. Deciphering the tree’s condition requires an up-close inspection, or testing a few branches. 

  • Dormant trees will have some buds on their branches, while dead trees will not.
  • If the tree has bark falling off and it’s not being replaced and/or has cracks in its trunk, it may be dead or dying.
  • If you scratch the bark of a dormant tree twig, you should find a moist, green layer. If scratching reveals a brown and brittle layer, repeat with another couple of twigs. If the twig is easy to snap, it’s another sign that the tree is not in good health. 

Common Tree Diseases

Trees are susceptible to a wide variety of diseases, depending on the location and species of tree. Here are some of the more serious tree diseases (and pests) that affect New York flora:

  • Beech Bark Disease results from an insect-fungus complex that affects Beech trees. It is often lethal to the tree. Symptoms include:
  • Beech Leaf Disease is a newly discovered often-lethal disease also affecting beech trees. Symptoms include:
    • Curled, striped, and/or leathery leaves
    • Decreased production of leaves and buds
    • Tree death
  • Oak Wilt is a fungal disease affecting oak trees. Red oaks die more quickly and spread the disease more effectively than white oaks. Symptoms are more noticeable in red oaks and include:
    • Leaves turning brown from the edges in
    • Sudden wilting in the spring and summer
    • Fungal spore mats under the bark after the tree dies
  • The Emerald Ash Borer can devastate entire forests of Ash trees. Symptoms include:
    • Sparse foliage
    • S-shaped galleries under the bark caused by larvae
    • Increased pecking by woodpeckers
  • The infamous Asian Longhorned Beetle is an invasive pest which can infect numerous tree species
  • Dutch Elm Disease almost wiped out the venerable American Elm. Symptoms include:
    • Flagging: the early summer discoloration and curling of leaves on high branches
    • Brown streaks under the bark
    • Laboratory confirmation is necessary to be 100% sure

What To Do

If you suspect that a tree is sick or dead:

  • Call the professionals (an arborist or a tree removal expert)
  • Stop using synthetic fertilizers
  • Take out soil covering the roots
  • Aerate the soil in the tree’s root zone
  • Add organic amendments to the soil

You can avoid dealing with the hassle of a dead or diseased tree in your garden by taking these steps:

  • Keep weed fertilizer away from their roots
  • Don’t apply mulch too close to them to avoid causing rot
  • If your area is experiencing a drought, water your trees
  • Don’t use sharp tools (such as lawnmowers) on areas of your lawn with exposed roots
  • If you decide to prune your tree, make sure you are doing it correctly first (i.e. do research or consult a professional)

Thank you for keeping an eye out for trees in need of help! 

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