FOREST PLANTING IN THE LAKE STATES 37 
the Lake States have been used for pasture and furnish examples 
of damage by domestic animals. The almost total failure of one 
plantation of Norway and northern white pine on a favorable site 
could be explained only as the result of the grazing of a band of 
sheep for two or three years after the plantation was established. 
Sheep and goats actually eat the foliage and are therefore likely 
to be more destructive than cattle or horses, which cause injury 
chiefly by trampling. The damage done by any kind of grazing 
animal in any one year may seem to be negligible, but over a period 
of years it is likely to mean the difference between success and failure 
of the timber crop. Studies in other parts of the country have shown 
that the degree of damage depends largely on the number of stock 
per unit area, and the way they are handled, the damage being 
greatest where they bunch together. The damage in a pasture which 
is overgrazed and where the feed becomes scarce is much greater 
than where the grass and more palatable herbage are abundant. It 
has been suggested that grazing is an advantage because it keeps 
down the grass and inflammable material and thereby reduces the 
danger of destruction by fire. This is undoubtedly true, but the 
risk of fire loss is not believed to be greater where reasonable protec- 
tion measures are provided than the possibility of serious loss of 
the planted trees through pasturing of domestic animals of any kind. 
INSECTS 
Insect damage to forest plantations appeared to be comparatively 
slight. In the plantations from 5 to 20 years old, only rarely was 
a tree found which was damaged by insects to the extent that it was 
likely to die. Jack pine appeared to be the most susceptible, 82 per 
cent of the plantations examined having been attacked. In many 
of them almost all of the trees were or had been infested by the jack 
pine form of the spruce bud worm, which attacked the new twigs in 
the early summer. 
Northern white pine is frequently attacked by the white pine wee- 
vil. The larvae feed on the terminal shoot under the bark and kill 
it. One or more of the side branches then become leaders, with the 
result that growth is retarded and the trunk usually develops a crook 
or fork. Forty-two per cent of the white pine plantations examined 
bore evidence of this insect, but rarely were more than 10 per cent 
of the trees attacked and in no case more than 20 per cent. Graham 
in a study of the weevil (25) concluded that, to avoid serious damage, 
northern white pine should be maintained in dense stands. Pierson, 
in New England, (51) came to the same conclusion and also sug- 
gested that northern white pine be grown in mixture with hardwoods 
such as oak, maple, and ash, the northern white pine to form not 
more than 20 to 25 per cent of the larger trees in the stand. 
Forty-seven per cent of the Norway spruce plantations bore evi- 
dence of damage by insects of one kind or another. A few of them 
were heavily infested by the spruce gall aphis (Chermes sp.), which 
causes a gall-like growth at the tips of the twigs. 
Norway pine is the least subject to insect damage of any of the 
planted species. Insect work was noted in only 12 per cent of the 
plantations. Only rarely were more than 2 per cent of the trees af- 
fected and then only slightly. 
