Forest ecosystems are subjected to many biotic and abiotic stresses. Native insects and diseases, droughts, windstorms, and wildfire periodically impact forests or specific tree species, leaving dead or weakened trees.
The effects of these stresses may be manifested locally or over a larger area, however they do not cause species extinction.
In contrast, foreign pests can threaten the continued existence of a tree species. This because tree species have not evolved genetic resistance to non-native pests, as the coevolutionary processes have not occurred.
Three prominent North American tree species, American chestnut (Castanea dentata ((Marsh.)) Borkh.), butternut (Juglans cinerea L.), and American elm (Ulmus americana L.) have been severely impacted by three non-native fungal diseases, chestnut blight (Cryphonectria parasitica), butternut canker (Sirococcus clavigigenti-juglandacearum), and Dutch elm disease (Ophiostoma u1mi and O. nova-ulmi).
Chestnut blight is a fungus that has virtually wiped out the American chestnut, as a commercial species, from eastern hardwood forests. Although stumps and roots from trees cut or killed many years ago continue to produce sprouts that survive to the sapling stage before being killed. The blight only attacks the part of the tree above ground. At present, there is no indication that a cure for this disease will be found. The fungus is widespread and continues to survive as a nonlethal parasite on chinkapin, Spanish chestnut, and post oak. Therefore, we must find a safe method to eradicate this blight.
As an aid to identifing tree diseases, blights, and other ways to help our forest trees, shade trees, and crop trees, use the YouTube video bank below.
These YouTube videos were produced by professional foresters, State University Extension departments, tree pathologists, and dendrology researchers.
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Please use subject heading: Forestry Technical Question
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This page was last updated June 26, 2013.