June, ’23 
HOUSER: DUSTING TALL TREES 
245 
number, were collected and placed in a container with unpoisoned elm 
leaves. Nine recovered and ten died. 
A considerable quantity of the dead caterpillars was taken from the 
sheet, tree trunks and nearby foliage and their bodies analyzed for ar¬ 
senic by Mr. C. H. Hunt of the Ohio Experiment Station. Mr. Hunt 
found arsenic present in large quantities, thus precluding the idea that 
the caterpillars might have been killed by the storm or have died from 
“wilt” or other disease. 
The final notes were taken May 31. Throughout the area which had 
received the double treatment, i. e., an additional dusting after the rain 
had washed off the first, the control of the caterpillars was almost 
perfect. It was difficult to find any living insects, and little additional 
injury seemed to have been done the foliage. In other words, the 
treatment seemed to have resulted in excellent commercial control. 
Since the foliage was damp at the time the poison was applied it “set” 
immediately and could be found as an excellent coating on leaves taken 
in all situations. 
In the area which had not received the double treatment, there were 
still on May 31 some cankerworm larvae feeding and the injury to the 
foliage had progressed somewhat. The application, however, un¬ 
doubtedly had been of value. 
Incidental Results 
An unanticipated aspect of airplane dusting was brought out in this 
test, viz: the consummate neatness of this method as compared with 
liquid spraying. With the latter there may be serious mutilation of 
choice plants by trampling of workmen, dragging of heavy hose and the 
passage of the machine. In many instances this is not a serious matter, 
but with property like the Severance estate, it is very important that 
expensive shrubbery, ferns, etc., be uninjured. 
When treated by airplane, the only visible evidence of the work was a 
slight deposit of powder on the foliage which did not in the least dis¬ 
figure even the most delicate plants and blossoms. 
The Casstown Test 
Because of lack of time but little of the detail of this test will be given. 
Briefly stated it consisted in the treatment of a 4-acre catalpa grove of 
3500 trees averaging about 25 feet in height. The plot was somewhat in 
the shape of an L with a difference in elevation of perhaps 70 feet be¬ 
tween the top of the stem and the foot. 
