The European Elm Scale 31 



With weaker solutions the percentage of efftciency fell rapidly. 

 A Scalecide solution of one in twenty gave an efficiency of 67 per cent 

 under similar conditions to those detailed above for the stronger mix- 

 tures. A solution of one part in thirty gave only 34 per cent. 

 Scalecide and Kerosene Emulsion.. A Summary and Some Inferences 



The atomizer experiments which I have detailed above were not ex- 

 tensive in character nor continued over any long period of time; but 

 they were thorough, and may well serve to indicate the relative effic- 

 iency of the two insecticides. I am confident that in order to penetrate 

 the white flocculent wax beneath the hibernating larvae, to penetrate 

 the deeper crevices in which they are hidden, or even to penetrate the 

 masses of semi-cocoons which shield so many of the hibernating larvae 

 one must use kerosene emulsion which is at least one-sixth pure kero- 

 sene ; one-fifth would be better. I cannot recommend the use of such 

 strong kerosene emulsions even on dormant elms. It seems to me that 

 if such strong emulsions were used for a series of years a serious in- 

 jury to the elms could not fail to follow. 



Much weaker solutions of Scalecide proved far more efficient and 

 it is likely that this insecticide can be \ised at a strength as low as 

 1 in 15 with thoroughly good results if the application wets the hiber- 

 nating larvae completely. "With this, as with the lime-sulphur, it 

 does not pay to economize material, as the main cost of spraying is in 

 the labor, and a poor job is worse than none, for it fails of effect and 

 gives the material and methods used a bad name. 



THE GARDEN HOSE AND THE ELM SCALE 



In this connection I would gladly make three points so clear that 

 there can be no possibility of a mistake concerning them. 



The first is this: The stream must have force. A gentle sprink- 

 ling probably simply refreshes the female scale insect and improves 

 her appetite. I have spoken of it as a hard stream, a stiff stream, a 

 strong stream, a powerful stream. I do not say that the insects are to 

 be simply wet, or given a chill, or even drowned out; but that they 

 must be hit hard and knocked out. 



My second point is this: The washing must le done thoroughly. 

 Most of the mature females are, indeed, to be found on the underside 

 of the lower branches ; yet there are others and many of them scattered 

 over the entire tree, in the axils of tiny twigs, on the under sides of 

 small horizontal branches high in the tree, and in cracks in the rough 

 bark of vertical limbs. In April wash every limb from twig to trunk, 

 then wash the trunk. Do it again in the beginning of June. 



My third point is this: The washing must he done at the right 



