A: Thanks for sending me photos of your oak tree; it helped me identify the problem right away. The orange growths on the limb of your oak are shelf fungi. The portion you see outside the tree is called the fruiting body of the fungi. The presence of the fruiting body on the outside indicates the limb is rotting from the inside out. Inside the limb can be found millions of thin white fibers called mycelium. Fungal mycelia have the ability to break down the wood fiber into material they can digest. The fungi may live off the tree for months or even years before the fruiting body appears on the outside. The presence of the fruiting body is a clue which reveals the limb may break off at any time. If the limb is hanging over a car or house or any other important structure consider removing it before it falls off and potentially causes damage. Certainly, this would not be the best place to put a picnic table either! Fungal shelves found on the trunks of trees or palms indicate the whole tree may be weakening and in danger of failing. There is no chemical application to cure this fungal growth; it is merely doing its job of breaking down dying matter. This is truly the full circle of life in action.

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