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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
mentioned a number of times in its relation to the control of the Euro¬ 
pean elm scale, Gossyparia spuria (Modeer). 
In 1907, Prof. S. B. Doten carried on a number of experiments 
with water and obtained satisfactory results in controlling this scale 
insect upon elm trees in Nevada. In fact he obtained better results 
than when he sprayed with lime-sulphur or kerosene emulsion. These 
experiments are listed in Nevada Bulletin No. 65, “The European 
Elm Scale.” 
In 1917, it became apparent to Mr. Burke and the writer that the 
elms at San Jose, Cal., were suffering considerably from a heavy 
infestation by this insect. Some of the trees on the State Normal 
School grounds were well infested. The attention of the head gardener, 
Mr. Hollingsworth, was called to this fact, whereupon it was decided 
that control measures should be instituted. The use of water was 
recommended, with the approval of Mr. Doten and the County 
Horticultural Commissioner, Mr. L. R. Cody. 
It was recommended that this be done in the spring after the females 
had become quite large, due to being full of eggs, and yet before many 
of the new elm leaves had unfolded to obstruct the force of water. 
There is but a short period when these conditions prevail. One gets 
some warning as to the time to do this by watching the fruit of the 
elm. The fruit matures and starts to fall a few days before the leaves 
unfold. This is the best time to do the washing, yet it may be done 
at any time until the females begin to lay eggs, which is seldom earlier 
than the last of May. However, some of the force of the water is 
dissipated when it hits the foliage and consequently the results are 
not as satisfactory. In 1918, the proper time to do the washing at 
San Jose was April 17 to 25. 
In preliminary experiments, different sorts of nozzles were tried 
out upon the garden hose, using the water from the one-inch hydrants 
upon the Normal School grounds. The maximum pressure available 
through these pipes was 50 pounds to the square inch at the pump 
and probably quite a bit less by the time it had reached the nozzle. 
The best nozzle that could be obtained for this pressure had a rather 
long taper with an outlet of an inch in diameter. It threw a solid 
stream and was found to be effective upon the scale insects up to a 
distance of 12 feet. 
On Small Trees 
This was used a number of times by the writer and Mr. H. E. Burke 
in 1918 and 1919 to very good advantage to wash the mature scale 
insects from young 8- or 10-foot elms. All the limbs were within easy 
reach and the trees were so small that a thorough washing was possible. 
