BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 7 
Sprays made from finely ground derris were more effective than those 
from emulsifiable rotenone extracts. 
FOREST INSECTS 
Outbreaks of Pine Bark Beetles in Western Forests Being Controlled 
The large-scale spray programs for the control of pine bark beetles 
in Idaho, Wyoming, and South Dakota conducted in the spring of 
1948 were very effective, according to surveys made in the fall. How- 
ever, there was a sharp increase in infestations on certain untreated 
areas. Control operations were again undertaken in the spring of 
1949. 
On the Black Hills and Harney National Forests in South Dakota 
the fall survey showed 16,000 ponderosa pine trees outside the treated 
area to be infested with Black Hills beetles. In Wyoming, where 
about 110,000 lodgepole pines in the Targhee-Teton area were treated 
in 1948, the infestation of mountain pine beetles was reduced by about 
75 percent. By treating these trees in 1949 it is hoped that the out- 
breaks will be cleaned up, or at least checked to the point where only a 
small amount of maintenance work will be needed annually. These 
control programs are being conducted by the Forest Service, the Na- 
tional Park Service, and State agencies, under the technical super- 
vision of this Bureau. 
Surveys in Colorado in the fall of 1948 showed an extensive out- 
break of the Black Hills beetle involving 23,000 ponderosa pine trees 
in the Roosevelt National Forest and a smaller outbreak in 4,500 trees 
in the Denver Mountain Parks area. 
Lodgepole pine stands in the Thompson River drainage of Montana 
were found to be seriously infested with the mountain pine beetle 
early in 1949. About 20,0(30 trees in an area of 35,000 acres were in- 
volved. Control operations were begun in June, private landowners 
paying their share of the costs. 
Another large outbreak of the mountain pine beetle in lodgepole 
pine on the Ashley and Wasatch National Forests in Utah was found 
to have increased from about 37,500 infested trees in 1937 to more than 
112,000 in 1948. Since timber values are relatively low in these for- 
ests, control is considered impractical. 
Bark Beetles Controlled Through Sanitation-Salvage Cuttings 
Ten years' testing of sanitation-salvage cuttings on the Black Moun- 
tain Experimental Forest have given results in bark beetle control that 
have far exceeded expectations. These cuttings remove from the for- 
est all trees that are of poor health, and thus deprive the beetles of 
trees in which to breed up populations of epidemic proportions. 
Through the cutting of 16 percent of the merchantable green-stand 
volume in trees of immediate risk to beetle attack, pine mortality has 
been reduced by 71 percent on 148 acres treated 10 years ago and by 
more than 87 percent on other areas treated from 6 to 9 years ago. 
This reduction represents a saving in pine volume of about 476 board- 
feet per acre over the period of the cutting. 
