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 



Fig. 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. 



