BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 15 
of Colorado. Some 784,000 trees on 33,000 acres were individually 
sprayed by Forest Service crews working under the technical direction 
of forest entomologists. Despite these efforts, about 1,500,000 ni'\v 
trees were infested. These will require treatment in 1951 if the out- 
break is to be kept within its present limits. Flight of beetles to new 
trees in 1951 will be greatly reduced as a result of the work in 1950. 
Observations in the infested areas showed that woodpeckers ate 
nearly all the beetles on trees in some outbreak centers, as well as 
beetles in trees in outlying localities. Three species of woodpeckers — 
the Alpine three-toed, the Rocky Mountain hairy, and the downy — 
were particularly effective in consuming bark beetles. 
The Engelmann spruce beetle has already killed more than 4% 
billion board feet of valuable timber. It is a threat to the remaining 
spruce stands of Colorado, northern New Mexico, and southern 
Wyoming. 
DDT Spray From Helicopter Controls White Pine Weevil 
Application from a helicopter of 2 pounds of DDT in 2 gallons 
of oil an acre to 225 acres of white-pine and Norway-spruce planta- 
tions in the Northeast in April 1950 resulted in excellent control of 
the white pine weevil. Previous attempts to control the insect by 
applying DDT from fixed-wing aircraft had been unsuccessful. 
Studies are being continued to determine the lasting effects of the 
insecticide and the period during which spray operations can be con- 
ducted successfully. 
DDT Spray From Helicopter Controls Pine Reproduction Weevil 
Excellent control of the pine reproduction weevil was obtained by 
spraying pines in brushfield plantings with DDT from a helicopter. 
In cooperation with the Forest Service 606 acres of plantings in three 
areas on the Lassen and Eldorado National Forests in California were 
sprayed. More than 90 percent of the weevils were killed and tree 
losses from weevil activit}^ were reduced by about 95 percent. The 
average acre cost was $2 for the helicopter and 87 cents for other 
items. 
Cheaper and More Effective Methods Developed for Airplane-Spray 
Experiments 
New apparatus, for installation in an airplane, that simultaneously 
disperses two separate sprays has greatly simplified the testing of 
arerial-spray equipment. In previous experimental work separate 
flights had been necessary for testing different equipment or different 
adjustments of equipment parts. This was not only expensive and 
time-consuming, it was unsatisfactory because no two flights could 
be made under identical weather conditions. It was known that 
variations in these conditions often affected spray deposits. To 
obtain valid results, therefore, it was necessary to study statistical 
data from a great many flights. With the new apparatus equally 
valid results may be obtained with one-tenth as many flights. 
972753 — 52 3 
