GOVERNMENT FOREST WORK 37 
become more numerous unless educational methods 
can be made effective. (Fig. 20.) 
SANITARY PRECAUTIONS IN THE NATIONAL 
FORESTS 
Precautions are taken by forest officers to protect 
the public health. All persons on national-forest lands 
are liable to trespass proceedings if insanitary condi- 
tions result from their presence. Forest officers en- 
t 
. 
force compliance with regulations on the part of all 
campers, stockmen, permittees, and other persons trav- 
eling through or occupying national-forest lands. 
CONTROL OF INSECT INFESTATIONS AND 
TREE DISEASES 
Aggregate losses in the forests of the United States 
from insect damage are enormous. The principal! for- 
est insect pests are tree-bark beeties and defoliating 
insects. In the former class are the western-pine 
beetles, the mountain-pine beetles, the Black Hills-pine 
-beetle, the Engelmann-spruce beetle, the southern-pine 
beetle, and the eastern-spruce beetle. In the Second 
class are the gypsy moth, the spruce bud worm, and 
the larch sawfly. Forest fires are frequently followed 
by beetle outbreaks, due to the enfeebled condition of 
the trees, which lowers their powers of resistance. 
Where insect attacks reach epidemic proportions on 
g s 
the national forests, ccntrol measures are undertaken 
in cooperation with the Bureau of Entomology. Ex- 
perimental work-in insect control also is carried on in 
cooperation with this bureau. 
Forest trees, like any other crop, are subject to 
attacks of fungous diseases. ‘“ Infantile” diseases, 
such as damping-off, are a factor in the destruction 
of seedling trees. At all ages trees are subject to 
canker diseases, root rots, etc., while after maturity 
heart rots rapidly reduce the timber content of the 
living tree, but by far the most serious menace of 
disease to forest crops at the present time lies in the 
imported parasite. Outstanding examples of this 
menace are the chestnut blight, imported from eastern 
