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Hypoxylon Tree Disease

Take a Look at Your Trees

As the weather warms chances are you'll find yourself spending more time outside enjoying mother nature. Whether landscaping is part of your job or you’re a weekend warrior, now is a good time to take a look at the plants on your property and make sure everything is in good shape.

If you keep a watchful eye on your landscaping, you've probably seen lichen in the past. Although most of us would rather not see fungus on our trees, lichens are harmless.

Lichens Evil Twin

Hypoxylon canker is a fungal disease native to many states in the US. Unlike lichen, Hypoxylon canker is a disease that will eventually kill its host. Hypoxylon canker essentially causes trees to die from dehydration.

Death by Dehydration

To understand how the fungus kills, we first need to cover some basic tree anatomy. The trunk of a tree does much more than simply support the branches. A tree trunk consists of four different layers. Each layer is responsible for carrying out specific tasks necessary for the tree’s survival.

Sapwood is the youngest of the four layers. It is the water carrier. Sapwood cells transport water absorbed by the roots through the trunk and two other areas of the tree.

This Lichen-like look-alike feeds on patches of sapwood causing them to die and making it difficult for the tree to get the water it needs.

Telltale Signs of a Hypoxylon Canker Victim

The initial signs of a Hypoxylon canker infestation are ambiguous and can be difficult to spot. Oftentimes, the first thing a property owner may notice is the crown of the tree becoming thinner. Death of twigs and branches in the crown of the tree is a symptom known as dieback. Dieback often goes hand in hand with many fungal infections.

As the infection worsens, signs of infestation become considerably easier to spot. Patches of bark will begin to fall off. Underneath the bark will be a soft, tan covering of conidia spores. The patch of spores will have a velvety soft texture.

The spores will most likely show up around the end of spring or the beginning of summer, and their coloration will begin to turn from gray to black as the season progresses from the end of summer and moves into the fall.

The final indicator will come from the tree's crown. The crown will continue to die off. Its leaves will turn a rusty shade of red. Once this stage is reached, the tree's death will most likely follow.

Distinguishing Harmless Friend from Deadly Foe

Telling the difference between a harmless fungus and a deadly foe is not as difficult as it might seem. At first glance the two specimens look very much the same. A closer look at how the fungus is growing on the tree will tell you all you need to know. Harmless lichen typically grows on the outermost surface of the bark.

A Hypoxylon canker is only visible after its growth causes the exterior bark of the tree to break loose. Upon closer inspection, you'll find this fatal fungus is actually growing on the interior layer of the tree trunk.

How Hypoxylon Canker Finds Its Host

Even though we'd like to credit human beings with the development of the first superhighway, mother nature beat us to the punch. It's amazing to follow the path of organic material such as spores from one area to another. Wind, water, and even furry or feathered creatures can help spores or seeds travel a great many miles before taking hold in an area.

Minimizing the Chance of Infection

There are two clich├ęs that come to mind when talking about how to prevent a Hypoxylon Canker infection. The best defense is a good offense and an ounce of prevention is better than a pound of cure.

There is no bulletproof way to ensure your trees don't fall victim to a Hypoxylon Canker. But if you'll remember, this deadly fungus typically only attacks weakened trees.

Part of the reason weak or unhealthy trees are the favorite victims of Hypoxylon Canker is because the spores make their way into the tree through wounds or openings. Whether the wounds are from improper pruning or parasites, keeping the tree free of wounds or holes limits the openings for spores to attack.

If Infection Has Taken Hold

If you find one of your trees has been infected there are currently no treatments to eradicate the fungus. Your best bet is to take steps to prevent the infection from spreading to other trees.

Here are a few rules of thumb for keeping your trees in good health and resistant to attack:

  • Apply 2 to 3 inches of mulch below the tree's drip-line
  • Keep the soil healthy and only fertilize when you must
  • Be sure to water when there has not been enough rainfall
  • Keep tree wounds to a minimum
  • Avoid unnecessary soil compaction

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