Windstorm Damage of May 20, 2001
Disease Makes Trees More Vulnerable to High Winds

Example 1: Shumard Oak in Fern Bluff MUD Greenbelt

Why did this tree fall, while most of its neighbors remained standing? Was the wind somehow more fierce around it? Or was this tree particularly vulnerable for some reason? In the analysis of this and other trees that were damaged in this wind storm, we will try to get to the bottom of these questions. 

Note in the photo below that the heartwood of this tree is rotten. A fungal wood-rot infection has attacked the interior of the tree. The darker section nearest the ground is soft to the touch, but the fungus infection has spread throughout the visible heartwood as far as the eye can see.

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This tree, a Shumard Oak (Quercus shumardii), has graced the banks of a wet-weather drainfield for perhaps 50 years. That drainfield is now a part of the Fern Bluff MUD, and serves to channel rainfall runoff safely into Brushy Creek. The Shumard Oak favors bottomlands, where it is more likely to obtain the moisture it craves. Trees of this species are very common here, where their graceful trunks and bright green foliage provide welcome shade from the hot summer sun.

The fungus infecting this tree is visible as white marks (these are the hyphae, or fungal filaments that develop as the fungus penetrates the tissues of its host) in the heartwood of the horizontal portion of the trunk shown below. The wood that has been invaded by the fungus has lost its natural resiliency because the fungus uses the structural components of its host for food. The strength of the oak tree is legendary, and much of that strength is normally supplied by the heartwood. This tree has lost that strength because its heartwood has become brittle and is easily fractured. Obviously, this kind of heart-rot fungal infection is devastating to the tree, even though it may not be obvious to an observer until the tree is toppled by a windstorm. 

Questions: Can we tell in advance if a tree is infected with this kind of fungus? Can something be done to prevent such an infection? Can a tree so infected be treated, perhaps even cured? We will be looking at these questions and more as this investigation continues.