Ask An Arborist: August 18, 2011
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Deformed Pine Trunk

Image submitted by reader

Tom Writes:

I have a relatively large pine tree in my yard that is about 20 feet from my house. It has several bad places on the trunk. Can you tell what they are and should the tree be removed?

Your pine tree has been infected with a fungus that has a very long scientific name, but that we commonly call fusiform rust (Cronartium quercuum f. sp. fusiforme). This disease has a very interesting life cycle that starts on a pine producing an orange powder in the spring. These spores do not cause the discolored, sunken areas on your pine. Instead these spores infect nearby oak trees where they cause some minor leaf spotting but no harm to the oak tree. The spores produced by the spots on the oaks return to the pine where they cause the cankers you are now seeing.

Not all pines are susceptible. Unfortunately, loblolly and slash pines are the trees most commonly afflicted and metro Atlanta sits in an area where infection rates approach 100%. Fusiform rust causes millions of dollars in damage to commercial pine growers not to mention the damage done to pines in the landscape and the wild.

The disease often outright kills young loblolly or slash pines and causes deformed areas on older trees. The cankers weaken that area of the trunk which can easily break when under the stress from wind or ice. There is no cure for this fungal disease once the tree is infected, but young trees can be protected before infection with the proper use of a fungicide containing the active ingredients triadimefon or myclobutanil. Other management practices would be to plant less susceptible pines such as shortleaf or longleaf pines.

As for Tom's pine tree, since it has numerous infection sites and is close to the house, I would recommend its removal.


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