December, ’20] 
HERBERT: WASHING FOR ELM SCALE 
475 
During all the following summer the trees remained quite clean, 
one or two showing evidence of a few scale insects by a slight drip. 
The writer estimated that about 85 per cent of the scales had been 
removed. However, one year later the trees were infested almost 
as badly as before the washing. Part of the reinfestation was due 
probably to the migration of young insects from all the surrounding 
well infested trees and partly from the estimated 15 per cent of insects 
left on the trees after the washing. 
Conclusions 
From these experiments the writer has concluded that the European 
elm scale on small trees can be treated very satisfactorily with the 
garden hose and nozzle and an average force of water. This is slower 
than spraying but is often easier than going to the trouble of obtaining 
the necessary apparatus for spraying where only a few trees are to be 
treated. 
With larger trees it is necessary to obtain a larger volume of water 
at a higher pressure in order to produce satisfactory results. This 
can be obtained by using a fire engine, but is recommended only when 
a large capacity power spraying outfit is not available. The former 
is cheaper but somewhat less effective. 
The ordinary orchard spray outfit is satisfactory for trees up to 35 
or 40 feet high, but larger shade tree sprayers are made which will 
reach 90 feet high or more. Trees 60 or more feet high would require 
30 to 40 gallons or perhaps more of spray material if properly covered, 
which would cost probably 5 cents per gallon by the time it was 
applied. Therefore the cost of spraying would be 25 to 50 per cent 
higher, but would probably be more satisfactory under the proper 
conditions. 
Chairman A. L. Melander: The meeting will now adjourn to 
meet at the same place tomorrow morning. Adjourned. 
Morning Session, Friday, June 18, 1920 
Chairman A. L. Melander: The first paper will be read by the 
Secretary, entitled “The Spread of the Argentine Ant in Southern 
California,” by R. S. Woglum and A. D. Borden. 
(Withdrawn for publication elsewhere) 
Chairman A. L. Melander: The next paper on the program is 
“Migratory Instincts of the Blue Bottle Maggots, Phormia regina,” 
by A. C. Burrill and H. L. Jones and will be read by the senior author, 
Mr. Burrill. 
(Withdrawn for publication elsewhere) 
