24 ANNUAL REPORTS OF DEPARTMENT 01 AGRICULTURE, I 
draulic sprayers; furthermore, the spray run-off is eliminated. On 
the other hand, there is less deposit on the lower part- of the crowns 
of i rees h ben I reated by helicopter. 
Highly Atomized lerial Spray Gives Most Uniform Distribution 
Further efforts were made to determine the degree of atomization 
most effective in airplane spraying of insect-infested forests. Sprays 
of three degrees of oneness were tested s <». 150, and 300 microns mass 
median diameter. The finest spray provided the mosl uniform dis- 
tribution across the swath and the least overdosing at point* 
maximum deposit in the swath. The percentage of spray reach- 
ing the ground was approximately the same for all three degrees 
of atomizat ion. 
Dyed Cards Used to Cheek Sufficiency of Aerial Spray Deposits 
Special paper cards coated witli a dry oil-soluble dyv are useful in 
intercepting falling spray and detecting unsprayed areas in aerial 
spraying operations. It is essential that unsprayed areas a- well as 
those receiving inadequate coverage be detected in airplane spraying 
operat ions against such forest insects as the spruce budworm. Re-runs 
by the spray planes are then made over such areas to assure their 
coverage. When a drop of .-pray fall- on the dyed card it makes a 
distinct circular mark on the card surface. The size of the drop and 
t he amount of spray it contains can then be est imated with sat isfactory 
accuracy by comparison with other card- previously treated with 
drops of known sizes and known quantities of spray. Under actual 
field conditions these cards have been read at the rate of 300 per 
man-hour. These experiments were performed in cooperation with 
the Division of Forest Biology, Canada Department of Agriculture. 
Benefits of Airplane Spraying for Spruce Budworm Control Per-i*t 
Surveys of the presence of the spruce budworm were made during 
L952 in several forest area- in Oregon and Washington that were 
sprayed in IK}!) and L950 by airplanes for spruce budworm control. 
With i he exception of -mall areas where spraying was done too late 
to he fully effective, it was found that control remained generally 
effect ive with no serious reinfestation. 
INSECTS AFFECTING MAN 
Mosquitoes Tested for Insecticide Resistance 
Outstanding results were obtained with EPN emulsion- or wet table 
powder spray- when applied with airplane- or ground equipment in 
field studies during the summer of L952 to determine tin 4 value of 
phosphate Insecticides for the control of insecticide-resistant mosqui- 
These investigations, in cooperation with the California De- 
partment of Health, were part of the continued study at the Corvallis, 
Dreg., laboratory to determine t he degree of resist a nee that mosquitoes 
have developed to DDT and other new insecticides. These studies 
were prompted by t be fact t hat cont rol of ( '"/< x tarsalis, A< <I< s ftigro*. 
