14 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE. 
On small trees this equipment was used to good advantage to wash 
the mature scale insects from their resting places. (Fig. 4.) All 
limbs were within easy reach and the trees so small that a thorough 
washing was possible. The results obtained were highly satisfac- 
tory and the trees remained clean until reinfested in the fall. 
On medium-sized trees the same apparatus was used, with the ad- 
dition of a 12-foot platform and a 7 or 8 foot extension rod. This 
proved to be too te- 
cious and was only 
moderately success- 
ful even when done- 
carefully. 
On large trees it 
yas necessary tog 
have a greater pres- © 
sure and volume of 
water in order to 
obtain satisfactory 
results. This was 
obtained by using a 
fire engine, supple- 
mented with 1,000 
feet of 23-inch hose, 
a short tapering noz- 
zle with a circular 
g-inch opening, and— 
a stand to facilitate 
holding the nozzle. 
(Fig. 5.) 
It was possible to 
use a pressure of 
160 pounds without 
doing any damage 
to the foliage al- 
ready out. It proved 
beneficial, in fact, by 
removing all dead 
twigs and branches 
and incidentally giv- 
Fre. 4.—Washing young elm tree with garden hose and ing the trees and 
nozzle to remove the European elm scale. lawns a good ITTrl- 
gating. 
The crew consisted of one foreman, one engineer, and three hose- 
men, this number being necessary in order to move the heavy hose 
without delay. te 
With this apparatus and crew 191 large trees were satisfactorily 
washed in six days at an approximate cost of $1.20 per tree. Dur- 
ing al] the following summer the trees remained very clean, one or 
two showing evidence of the presence of a few scale insects by a 
shght drip. The writer estimated that about 85 per cent of the 
scales had been removed. One year later, however, the trees were 
again infested rather badly, owing partly to the remaining 15 per 
cent and to a reinfestation from the surrounding well-infested trees. 
