December, ’20] 
HERBERT: WASHING FOR ELM SCALE 
471 
Owing to the difference in the equipment of the machines and other 
factors which had a marked influence upon the work done by the in¬ 
dividual machines, it was necessary to express this in nozzle acres per 
calendar day in order to get an adequate idea of the work done. 
The term nozzle acre per day indicates the number of acres sprayed 
by one nozzle in one calendar day based on the number of days in the 
spraying season. 
The average nozzle acres per day for all company owned machines 
was 1.41. At this rate a 12-nozzle machine would cover 16.92 acres 
per day. During the height of the season such machines covered 
from 30 acres for 10-hour day to 90 acres per calendar day. Many 
machines were operated all night. Headlights were placed on them 
which were run by storage batteries from automobiles. 
Sixty-one per cent of the entire 180,295 infested acres were sprayed 
with company owned sprayers. The Sugar Company purchased 
nearly a million and a quarter pounds of insecticide during the season. 
The results of this attempt at controlling a sugar beet pest through 
cooperation of the Sugar Company and the beet growers were so suc¬ 
cessful that in spite of the probable reduction in the number of worms 
attacking the beets this (1920) season more sprayers are being pur¬ 
chased and several new forms of insecticide are being secured for 
experimental purposes. 
During the season of 1919 Paris green, arsenate of lead, calcium 
arsenite and several other forms of insecticide were used. The Paris 
green gave by far the quickest and best results. This was used at the 
rate of 3.5 to 4 pounds per acre. This appears unusually heavy until 
we consider the great leaf area of an acre of beets and the need of 
quick results. Including cost of Paris green, labor and sprayer rental, 
the cost per acre was about $3.50. A timely and successful applica¬ 
tion of insecticide would mean, on the average, not less than two tons 
more of beets per acre. This at $10 per ton, the price paid in 1919, 
is $20 per acre or a profit of over 400 per cent on the investment. 
Chairman A. L. Melander: The paper entitled “ Results of 
Washing Experiments for Control of the European Elm Scale” will 
be read by the Secretary. 
RESULTS OF WASHING EXPERIMENTS FOR CONTROL OF 
THE EUROPEAN ELM SCALE 
By Frank B. Herbert, Forest Insect Laboratory, Los Gatos, Cal. 1 
A solid stream of water has been recognized for some time as being 
of some value in the control of certain soft bodied insects. It has been 
1 Forest insect investigations, U. S. Bureau of Entomology. 
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