EXPERIMENT STATION REPORT. 645 



been pro'posed and used with greater or less success. The 

 kerosene emulsion with milk and soap, first prepared in the 

 course of the work of the Entomological Division of the United 

 States Department of Agriculture, is of course well known, and 

 has been widely and successfully used. But there was the work 

 of preparation, and the fact that, withotit soft water, it was 

 difficult tO' get any emulsion at all. The farmer or fruit grower 

 does not ordinarily like to make complicated mixtures, or those 

 requiring any special apparatus for preparation. Hence, the 

 kerosene emulsion was never given the wd-de use that its merits 

 deserve. Used as a winter wash as against the pernicious scale, 

 it developed that, when used m a dilution containing 15 to 20 

 per cent, of kerosene it was much more injurious to trees than 

 even undiluted kerosene; hence, its application tO' this purpose 

 was ne\er urged. More recently, especially through the efforts 

 and experiments of Dr. Howard E. Weed, now of New Hamp- 

 shire, the idea of a mechanical mixture of kerosene and water 

 was developed, and after many experiments, pumps so arranged 

 as to spray kerosene or other oils a'lid water in definite propor- 

 tions were put uptm the market by a number of manufacturers. 

 These pumps were intended to bring to the nozzle oil and water 

 in uniform proportions, the globules of oil and water so mingled 

 as they emerged from the nozzle that the effect would be that 

 of a verv thin, evenly distributed coating of oil, which would be 

 sufficient to kill insects, yet not enough to injure vegetation. 

 This gave the oil a much more extended field, and a large num- 

 ber of emulsion pumps, knapsack, barrel and tripod, were soon 

 in general use. As a whole the results were good ; biit even the 

 best o( the pumps proved erratic in action sooner or later. Of 

 two pumps of the same make one would work beautifully when 

 received ; the other would be unreliable from the start ; or an 

 obstruction to one pump or valve would result in an application 

 of all water or all oil. or a percentage different from that in- 

 tended, and the consequences would be either injury to' the tree 

 or lack of effect^ agaii^st -the insects. Nevertheless, much good 

 was accomplished with combination or emulsion sprats, coutain- 

 ing 20 to 25 per cent, of kerosene, and these were usually safe 

 upon trees and shrubs of all kinds. Piut the necessity for a 

 special pump, even if it could be disconnected so^ as to be used 

 for a simple mixture was a drawback, and there was real de- 

 mand for some method of using the oil without all the bother of 

 either an emulsion or special pump. 



When the ([uestion of dealing with mosquito larv:e arose one 



