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[Images] Five photos of different landscape

Compass issue 10
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Compass is a quarterly publication of the USDA Forest Service's Southern Research Station (SRS). As part of the Nation's largest forestry research organization -- USDA Forest Service Research and Development -- SRS serves 13 Southern States and beyond. The Station's 130 scienists work in more than 20 units located across the region at Federal laboratories, universites, and experimental forests.

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Issue 11

Chestnut Blight

Chestnut blight is caused by Cryphonectria parasitica, a member of the largest group of fungi, the ascomycetes. C. parasitica enters through cracks in chestnut bark and through wounds, causing dead areas on bark called cankers. Once introduced, the fungus grows rapidly, producing a network of filaments called mycelial fans that quickly girdle the tree and grow down into the wood, where they destroy the vascular systems that carry sap. The leaves on the stem then die, showing the symptoms that give rise to the name “chestnut blight.”

When the cankers grow into the wood, the fungus forms bright orange, rounded structures on the surface of the bark. These stromata produce two types of spores—ascospores and conidia. Ascospores appear whenever conditions are right, and are forcibly expelled from the stromata to be carried away on the wind. The second spore types, conidia, ooze out after rain and can be carried by waterdrops or on the feet of insects, birds, squirrels, and other creatures.

Adapted from: Hebard, F.V.; Double, M.L.; MacDonald, W.L. 2007. A pathogen without rival. In: Bolgiano, Chris, ed. Mighty giants: an American chestnut anthology. Bennington, VT: The American Chestnut Foundation: 172174.

One type of wildland-urban interface is the isolated interface, where second homes are scattered across remote areas.
Chestnut sprouts with blight. (Photo courtesy of The American Chestnut Foundation)