15 
THE COTTONY MAPLE SCALE 
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recommended and used in the parks of Denver. In July, 1905, I care¬ 
fully examined Fuller park which had been treated in this way and 
was surprised to find it clean. Not more than a dozen of the cottony 
masses were to be found and there w r ere practically no scales on the 
leaves. A reexamination of the same park in January, 1906, however, 
showed that almost every tree was infested with a few scattering 
females, which proved, I think, that the eradication of the scale is a 
practical impossiblity. 
The climate of Denver is much drier than that found in most 
parts ol the insect’s range. The last set of experiments, however, were 
conducted during a wet period, but the results did not appear to be 
seriously affected. Mr. Braucher writes me that kerosene emulsion 
has been used in the Chicago parks about twenty per cent in strength 
with most excellent results. 
The winter treatment is the ideal one from a number of considera¬ 
tions. The insects are more easily reached, for the twigs and limbs are 
exposed. Insecticides may be used in sufficient strength to kill with¬ 
out injury to the tree. The hibernating females are generally on the 
under sides of the limbs and most abundant on the lower branches, 
which makes the application more easy. The amount of insecticide 
required is less than half what it would be in summer. 
To Summarize. —The cottony maple scale may be controlled by a 
winter treatment of kerosene emulsion fifteen per cent or greater in 
strength, and probably by whale oil soap at the rate of one pound to one 
gallon. It may be necessary to use a higher percentage of kerosene 
where the climatic conditions are unfavorable. Eradication of the 
scale is not to be expected and only such trees and areas should be 
treated as are threatened with serious injury. 
Too great stress cannot be laid on the thoroughness of the work. 
The tree should be treated from both sides and from beneath each 
limb. After treatment each tree should be carefully inspected and the 
missed spots “touched up.” 
The kerosene emulsion should be carefully made. It is better to 
use more soap than the ordinary formula, since soaps vary somewhat 
in emulsifying powers and the satisfaction of a good emulsion more 
than repays the slight extra cost. During 1906, the Denver park 
authorities used in part a soft naptha soap. Twigs which had been 
treated with this emulsion were sent to this office and examination 
showed all the insects to be dead. 
