BLIGHT SPREAD

Chestnut blight was first described in the Bronx Zoo in 1904 but had probably been killing American chestnut trees in scattered pockets across the eastern seaboard for several years prior to that date. Nut bearing Japanese chestnut cultivars, with fruits larger than their native cousin, were widely available in the nursery trade of the day. Parsons Nursery in Flushing, N.Y. was the first to offer grafted trees in 1876, but by the end of the century several other selections had been imported by different nurseries.

By 1912, the epidemic had swept across most of New England and Pennsylvania, leaving 100-foot tall skeletons of American chestnuts in its wake. By 1940, the fungus had spread throughout the range of the American chestnut and jumped to the Ozark Chinquapin (Castanea pumila var. ozarkensis) where it continued its destructive ways.  When the blight was first identified in the early 1900’s, scientists knew very little about this new disease. Today, much more is known about the chestnut blight and the fungus pathogen that causes it, Cryphonectria parasitica.  Cryphonectria parasitica is a member of the Ascomycetes group of fungi, many of which are parasitic, including Dutch elm disease and oak wilt fungi. The same fungus that attacks American chestnuts also devastated Ozark chinquapin and is mildly pathogenic on Allegheny chinkapin and scarlet oaks.

The disease attacks the cambium region of the tree, killing the top completely but allowing trunk suckers to regrow from the base. These suckers often reach the diameter of a man’s leg when they are again killed back to the ground. After several cycles of this kind of attack, the tree that used to coexist with oaks and hickories as an equal now is little more than a shrub in the under-story of the forest.