BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 23 
WESTERN PINE BEETLE 
Encouraged by the results secured in recent years from well-planned extensive 
control operations the Forest Service, Park Service, Bureau of Indian Affairs, 
and private timber owners have been especially active during the last year in 
the control of the western pine beetle. In Oregon and Washington over 250,000 
acres of pine timberland were covered with control work. A similar enthusiasm 
among both public and private protective agencies is also evident in California. 
In northern California the McCloud River Lumber Co. has committed itself to 
the policy of cutting and milling infested trees and destroying the infested bark. 
Although the timber thus salvaged contains considerable blue stain, there is a 
market tor it, and from the standpoint of cost this method is much more advan- 
tageous than the wasteful one of burning the infested bark and leaving the logs 
to rot in the forests. 
OTHER BARK BEETLES 
Control operations against the Black Hills beetle in several forests in Colo- 
rado, against the Douglas fir beetle in Wyoming, and minor operations against 
threatening infestations of several species of Ips in a number of localities have 
also been carried through. 
RESEARCH ACTIVITIES 
Research work directed toward the development of more efficient and eco- 
nomical control methods against bark beetles has been continued, and in some 
cases slight modifications of previously used methods have led to excellent 
results. One such modification is based on the principle of preserving a larger 
percentage of the natural enemies of the mountain pine beetle, to bring about 
not only a numerical reduction of the pest but also a more favorable relation 
between parasite and host, thus assuring more lasting benefit from the control 
operation. Encouraging results have continued from experiments in killing bark 
beetles by means of penetrating oils applied to the bark and by the introduction 
of lethal materials in the sap stream of infested trees, but the methods are not 
yet sufficiently perfected to warrant their use in large-scale control projects. 
The continued demand for nursery stock due to the remarkable activity of 
the reforestation program in connection with the Forest Service and with the 
various emergency activities, such as the erosion control work, the shelter- 
belt program, the Civilian Conservation Corps work, etc., has made the con- 
trol of insects affecting forest nursery stock and newly established plantations 
of vital importance. Of the numerous insects important in these connections, 
the white grubs are by all odds the most destructive. A thorough investiga- 
tion of these insects is under way, involving not only a study of their biologies, 
but also the development of control methods which will kill the grubs but 
will not injure the young trees. The nursery work is largely centered in 
the Southeastern States, while the work in plantations is centered in the Lake 
States. 
The investigations on the locust borer in the Central States were continued 
along the line of preserving stands by means of stimulating new growth of 
trees from sprout growth following cutting of the badly infested trees and by 
mulching. The projects on the southern pine beetle, the white pine weevil, 
the beech coccus, the larch case bearer, the leaf-mining sawfly, the elm leaf 
beetle, and other native and introduced insect pests of trees in the East have 
also been considerably advanced. An extensive survey of the New England 
States to determine the occurrence of the balsam bark louse was made, and 
experiments in control, applicable to infested balsam trees used as ornamentals, 
were successfully conducted. 
The work upon the insects associated with the Dutch elm disease has been 
greatly enlarged by the transfer of seven men to the Morristown, N. J., labora- 
tory from the old Melrose Highlands, Mass., laboratory, and the employment 
of additional men on emergency funds. During the ye'ar a great amount of 
biological work has been done upon various insects found in elm, and much 
experimental work performed to determine insect vectors, with special refer- 
ence to those which injure the bark either in feeding, ovipositing, or in the 
construction of brood burrows. During the year, as a result of field, labora- 
tory, and greenhouse experiments, 50 cases of successful transmission of Cerato- 
stomclla ulmi by the smaller European elm bark beetle (Scolytus multistria- 
