friend: spruce sawfly, pine shoot moth 
51 
group of closely planted trees is infested after the branches close, those 
on the periphery of the group suffer more than those inside. Slowly 
growing trees are more seriously affected than those growing rapidly. 
The death of terminal buds and shoots causes latent buds to develop 
below the tips, giving the tree a bushy appearance. The shoots pro¬ 
duced by these latent buds become infested in turn, and the bushiness 
may become accentuated. Moreover, if the infestation persists, shoots 
are killed more rapidly than they are produced, and loss of foliage and 
height growth ensue. Pines on poor soils become bushy and stunted 
more quickly than vigorously growing trees. Distortion of the bole of 
the tree, a result of shoot injury in the spring, is quite common. A 
heavy infestation may kill all the needles in the upper foot of the termi¬ 
nal of the tree, resulting in the death of this part of the main stem. It 
has been estimated that a population of 50 to 80 larvae per tree in the 
fall, or about 25 adults per tree in the spring, is sufficient to severely 
injure a red pine of any size from 6 to 25 feet. The concentration of 
larvae in the tops of the trees accounts for the severity of the attack on 
large specimens. It takes from three to five years for the shoot moth, 
once established, to reach this population density on red pine. 
On mugho pines the infestation is commonly heavy but the effect is 
frequently less severe. This is due to the bushy type of growth in this 
tree. That is, it often does not look so bad as red pine when several 
shoots are killed. However, mugho pine is often badly disfigured by 
an abundance of dead tips. 
The cold weather in winter has a marked effect on the survival of 
larvae. When the temperature drops below -10° F. the larval mor¬ 
tality is high, and at -17° F. it may be complete. This limits the abund¬ 
ance of the insect in northern New York and New England. 
Control on shade trees may be attained by spraying or by removing 
infested buds and shoots. Two applications of a mixture of one pound 
of powdered skim milk and four pounds of ground derris or cube in 100 
gallons of water, the first application during the last week of June or 
the first week of July, the second 10 days later, have given excellent 
results on red pine. If the trees are so low that all parts can be reached 
from the ground, and are few in number, the infested buds and shoots 
containing the larvae may be removed and destroyed. This is most 
easily accomplished in May, when the infested shoots are conspicuous. 
It is practically impossible to successfully treat mugho pine in this man¬ 
ner at any other time, because there is a natural exudation of pitch from 
