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 i n c h in 

 length. Eggs are 

 laid in the fall and 

 overwinter u n d e r 

 the female scale. 

 These hatch late in 

 the spring, and the 

 n e w scales became 

 full grown by mid- 

 summer. An oil and 

 nicotine spray will 

 control this species 

 if applied late in tliQ 

 spring when the ^gg^ 

 are hatching. 



The California pine scale (Aspidiotus pini Comst.) is 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 hare 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 yelloAvish 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. 



Figure 22. — The pine needle scale (CJiionaspi^ pinifoliae 



