106 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
Direct control methods consist in felling the infested trees and 
either peeling the bark from the trunk or burning the bark either 
on or off the trunk. In the southern part of ‘its range effective 
destruction of the broods in thin-bark lodgepole pine can be secured | 
by felling the trees, trimming off the branches, and exposing the 
trunks to the sun’s rays. Under certain conditions spraying the 
standing trees with fuel oil and burning them without felling has 
been found to be inexpensive and effective. Control operations are 
usually undertaken in the spring of the year. Peeling must be dis- 
continued when the broods pupate. Burning can be continued until 
the start of emergence or until the fire hazard becomes too great. 
FIGURD 53.—Severe damage to ponderosa pine in the Kaibab National Forest, Ariz., from 
attack by the Black Hills beetle. (Blackman.) 
The Black Hills beetle (Dendroctonus ponderosae Hopk.) (6) is 
the most aggressive and destructive insect enemy of ponderosa pine 
in the Rocky Mountain region. It is distributed from the Black 
Hills of South Dakota (whence it received its name) to eastern 
Montana and south through eastern Wyoming, Colorado, Utah, 
Arizona, and New Mexico. Under normal conditions it 1s compara- 
tively rare and found only in weakened, decadent trees. Period- 
ically, however, its numbers increase to epidemic proportions and 
these sweep through the ponderosa pine stands, killing small to large 
groups in ever-increasing numbers, until as much as 50 to 90 per- 
