364 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
standing chestnut timber. The estimate of $25,000,000 made in 1911 
as representing the loss up to that time was probably much too con- 
servative. But the total loss to date is insignificant compared with 
the loss which will ensue if the disease once attacks the fine chest- 
nut timber of the South Appalachians. The bark disease has 
killed all the chestnut trees in those localities where it has been 
present long enough, and there is not now the slightest indication 
that it is decreasing in virulence or that the climate of any region 
to which it has spread is having any appreciable retarding effect 
upon it. 
CAUSE AND SYMPTOMS. 
The chestnut bark disease is caused by the growth in the bark and 
outer wood layers of a parasitic fungus, L'ndothia parasitica ( Murr.) 
A.and A. 
When any spores of this fungus gain entrance into a wound on 
any part of the trunk or limbs of a chestnut tree they commonly give 
rise to a concentrically spreading canker which soon girdles the tree. 
(Pl. XXXIV.) Not only is the bark and cambium destroyed, but the 
fungus quickly infects the outer layers of sapwood, penetrating more 
deeply at the center of the canker. If the part attacked happens to 
be the trunk, the whole tree is killed, sometimes in as short a time as 
a single season. If the smaller branches are attacked, only those 
portions beyond the point of attack are killed, and the remainder of 
the tree may survive for several years. In Plate XXXVI, figure 3, 
the lower large limb on the left-hand side is still healthy, as the 
canker which girdled and killed the rest of the tree is situated on the 
trunk immediately above this branch. Plate XXXVI, figure 1, shows 
the ragged appearance of the tree, due to the fact that some branches 
are not yet girdled and still have normal foliage, while others are 
dead. 
Some of the symptoms are quite prominent. Limbs and trunks 
with smooth bark which are attacked by the fungus soon show 
cankers in the form of dead, discolored, sunken areas (occasionally 
with a raised margin), which. continue to enlarge and soon become 
covered more or less thickly with yellow, orange, or reddish brown 
spots about the size of a pinhead. (Pl..XX XIV.) These spots are 
the pustules of the fruiting fungus. Following a rain, or in damp 
situations, masses of minute spores (conidia) are commonly extruded 
in the form of long, irregularly twisted strings or horns, which are 
at first bright yellow to greenish yellow, or even buff, becoming 
darker with age. If the canker is on the trunk or a large limb with 
very thick bark there is no obvious change in the external appear- 
ance of the bark itself, but the pustules show in the cracks, and the 
bark often sounds hollow when tapped. After the limbs or trunks 
