50 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
carry the smoke from mills. The choking of stomata in the leaves 
by foreign particles probably renders them susceptible to these insects. 
Scale insects are controlled through the use of contact sprays (35), 
such as miscible oils, distillate or petroleum emulsions, and in orchard 
work by fumigation. None of these methods are practical under 
forest conditions, but fortunately none of the scale insects attacking 
forest trees have become serious enough to call for control. 
The pine needle scale (Chionaspis pinifoliae Fitch) (fig. 22) is prob- 
ably the scale most commonly found on the foliage of western conifers. 
It occurs throughout 
the Western States, 
where it attacks all 
species of pine and 
sometimes Douglas 
fir, spruce, and cedar. 
Small trees, saplings, 
and poles, especially 
along dusty roads, 
are often so heavily 
infested that the foli- 
age appears white. 
In some cases trees 
have been killed by 
the attack. The ma- 
ture scales are small, 
nearly pure white, 
elongated, and about 
one-eighth inch in 
length. Eggs are 
laid in the fall and 
overwinter under 
the female scale. 
These hatch late in 
the spring, and the 
new scales became 
full grown by mid- 
summer, An oil and 
nicotine spray will 
control this species 
: : if apphed late in the 
FIGURE 22.—The pine needle scale (Chionaspis pinifoliae). spring when the eggs 
are hatching. 
The California pine scale (Aspidiotus pini Comst.) 1s often asso- 
ciated with the pine leaf scale in its attack on various pines, and it 
is also found in abundance on Douglas fir and hemlock and may 
attack other conifers. Many young pines in California have been 
killed by this scale. It is distributed over most of North America. 
The mature scales are almost circular, about one-sixteenth of an 
inch in diameter, and yellowish brown to black. The young hatch 
early in the spring and summer and settle upon the new needles of 
the host. From one to three generations are produced during the 
year, and the winter is passed in a half-grown condition. 
