26 MISC. PUBLICATION 162, U. S. DEPT. OF AGRICULTURE 
Funcus DISEASES 
Fungi attack the forest in many ways. Some kill the roots of the 
trees; some grow upward from the ground into the trees and change 
the sound wood of the trunks to a useless rotten mass. The chestnut 
bark disease, or chestnut blight, has ravaged the native chestnut in 
this country. It is a parasitic fungus, introduced from Asia on small 
nursery stock before this country had enacted plant quarantine laws. 
Its minute spores float through the air and spread the disease. The 
spores find lodgment in the bark and the fungus gradually grows down 
through it, eventually causing the death of the tree. As yet no prac- 
ticable means of controlling the chestnut bark disease has been found. 
Another fungus disease is the white pine blister rust which, strange 
as it may seem, lives alternately on the pine and on currant and goose- 
berry plants. The disease enters the white pines through the needles 
and grows into the bark. Diseased areas in the bark are called cankers. 
About 3 years after a tree becomes infected orange-yellow blisters 
break from the cankers. In the spring millions of spores from these 
blisters are scattered by the wind over long distances, infecting the 
leaves of currant and gooseberry bushes. The disease cannot go di- 
rectly from one pine to another, but must first go to currants or goose- 
berries. It is the spores produced on the leaves of these plants that 
are dangerous to the pine trees. Since these spores are delicate and 
short-lived their infecting range is limited to relatively short distances. 
Thus it is possible to control the disease locally by destroying currants 
and gooseberries in the vicinity of white pines. 
OTHER ENEMIES 
Animals grazing in the woods can do serious damage to both the 
mature trees and the young growth. ‘The older trees may be injured 
by having their roots trampled and wounded and by having the soil 
around them compacted to such an extent that it is nearly impervious 
to water. Young growth is often entirely destroyed. Cattle, horses, 
sheep, and goats browse young seedlings, particularly the hardwoods, 
trample them down, or brush against them and break them. Hogs eat 
the seed of certain trees and thus prevent new growth from starting. 
They actually root pine seedlings out of the ground and eat the inner 
bark. Grazing in woodlands should therefore be carefully regulated 
if the stand is to remain productive. 
In localities where trees are shallow-rooted, or the ground is soft 
because it is soaked with water, or where trees have been weakened by 
fire or other agencies, windstorms can cause extensive damage. The 
New England hurricane of 1938 blew down millions of board feet of 
timber over wide areas; the huge timber salvage job which followed 
lasted several years. A bad blow-down may become a fire menace, as 
well as a waste of valuable timber. 
Snow and sleet may also be very harmful, especially to young trees. 
It often loads them down, breaks, or deforms them, especially if wet 
snow falls heavily before the broadleaf trees have shed their foliage 
in the fall. In east Texas in 1944 an ice storm damaged timber on 
several million acres. In many regions, however, snow is so useful in 
protecting the soil and the young trees that the harm it does is offset 
by its benefits. 
