16 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE. 
trees need to be rid of this pest. The ordinary pressure of water 
from the hydrant will remove the insects at a distance of 10 or 12 _ 
feet. Each limb and twig must be hit with a solid stream of water 
from at least two directions. The use of a fire engine and equipment 
is quite satisfactory on trees over 20 feet high. It probably does not 
produce as good results as when a high-capacity spray, outfit is used, 
but when the former is available and the latter is not, it is recom- 
mended for large trees. It is cheaper than spraying and can not 
damage the elms. 
All washing should be done in the spring just before the leaves 
appear on the trees, usually about the middle of April. The fruits 
Fic. 6.— Spraying large elms with high-power outfit to remove the European elm scale. 
or small winged seeds begin falling from the trees about a week 
before the leaves appear, thus providing a warning that the washing 
should be done soon. At this time the female scales are large, being 
full of eggs, and are easily washed from the trees. This washing 
could be done at any time until egg laying begins, five or six weeks 
later, were it not for the presence of the foliage, which impedes the 
force of the stream. Thus to insure success in washing there must be 
a solid, forceful stream of water, and it must be used at the proper 
time. 
