INSECT ENEMIES OF WESTERN FORESTS 



105 



May and June, when expanding fir buds exposed the small bud- 

 worm larvae to insect enemies and sprays. In 1949, 267,000 acres 

 were treated at a cost of $1.20 per acre, and in 1950, about 

 933,700 acres at $1.06 per acre. These spray operations reduced 

 the infestations by 97 to 99 percent. 



The sugar pine tortrix (Choristoneura fumiferana var. lamber- 

 tianae (Busck) ) (fig. 45) is at times very destructive to the new 



Figure 45. — The sugar pine tortrix (Choristoneura fumiferana lambertianae) 

 and its damage to sugar pine terminals. 



buds and pollen bodies of sugar pine, killing as much as 90 percent 

 of the new growth on the trees. The caterpillars feed in colonies 

 within a web on the terminal shoots and transform to adults in 

 July. The adults are speckled tan-to-golden moths with a wing 

 expanse of about % inch. 



The black-headed budworm (Acleris variana (Fern.)) (U, 135) 

 is an important defoliator of hemlock, true fir, and spruce forests 

 in the northern part of the United States, Canada, and Alaska. In 

 the Northeast and in eastern Canada it has appeared in destruc- 

 tive numbers only where mature true fir forms a high percentage 

 of the stand. 



