. Chestnut blight. Chestnut blight; Chestnut. FARMERS' BULLETIN 2 0 68 damage. The fungus sometimes grows oil dead chestnut oak, red maple, shagbark hickory, and stag- horn sumac. In Europe, it has at- tacked three of the native oak species. THE BLIGHT FUNGUS The blight fungus grows mainly in the bark of cJiestnut trees, form- ing masses of flattened threadlike strands, called mycelia. Mycelial strands feed upon and kill the bark tissues. They advance through the bark much as plant roots advance. FiociiE .",.—Myoelinl fans of the chestnut blight fungus, revealed by wraiiing away tlie oute
. Chestnut blight. Chestnut blight; Chestnut. FARMERS' BULLETIN 2 0 68 damage. The fungus sometimes grows oil dead chestnut oak, red maple, shagbark hickory, and stag- horn sumac. In Europe, it has at- tacked three of the native oak species. THE BLIGHT FUNGUS The blight fungus grows mainly in the bark of cJiestnut trees, form- ing masses of flattened threadlike strands, called mycelia. Mycelial strands feed upon and kill the bark tissues. They advance through the bark much as plant roots advance. FiociiE .",.—Myoelinl fans of the chestnut blight fungus, revealed by wraiiing away tlie outer froru part of a cankered chestnut stem. through the soil, and form buff-col- ored mats or fans in the bark and cambium (fig. 3). The fungus continues to grow around chestnut trunks or limbs until it encircles them. The alfected parts then die. The fungus forms fruiting bod- ies, or blisters, in and on dying and dead bark. These blisters look like yellow, orange, or red-brown pin- heads dotted over the surface of the cankers (fig. 4). They bear micro- scopic sjDores, which correspond to the seeds of higher plants. Spores of one type, called pycnidiospores, are produced within some of the blisters in great numbers. In damp weather they are forced out in slender sticky ribbons, much as l)aste is squeezed from a tube. They then form tiny yellowish or orange- colored hairlike tendrils, called spore horns (fig. 5). Spoi'es of this type, being sticky, adhere to insects, birds, and other animals and thus may be carried for long distances. Rain washes them into wormholes and wounds in tree stems and branches, where new infections may develop. Blisters producing spores of a second type, called ascos])ores, are made up of flask-shaped structures with very small openings. These s]iores do not form spore horns. They are borne within the flasks in groups of eight, each group en- closed in a thin, transparent sac. lender favorable conditions of mois- ture and temperature, the sacs
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Keywords: ., bookcolle, bookcollectionbiodiversity, booksubjectchestnutblight
