August, '22] LEACH & brinley: Japanese beetle, contact insecticides 303 



Japanese beetle by contact. A series of tests were accordingly con- 

 ducted during the season of 1920 and 1921 in order to determine the 

 factors influencing the use of soap alone and combined with other 

 materials when employed as a contact spray for the control of the Jap- 

 anese beetle, and the Rose beetle {Macrodactylus subspinosus) . 



An efficient contact spray will no doubt have considerable appli- 

 cation in the control of the Japanese beetle at this time, due to the 

 fact that a suitable arsenical spray has not as yet been developed. 

 The gregarious feeding habit of the beetle is also conducive to securing 

 a large kill by the use of a small quantity of contact spray on a limited 

 amount of foliage, since the beetles cluster thickly on grape vines, 

 sweet cherries and smartweed, mainly feeding exposed on the upper 

 surfaces of the leaves where they are readily wetted by a contact spray. 



Materials Employed 



During the course of the experimental work the writers tested the 

 various types of soaps. These included fish oil, rosin fish oil, laundry, 

 borax, sodium hard and soft, and potassium soft soa'-'s. The results 

 indicate that the type of soap is not as important as is the concen- 

 tration of the spray solution although certain types oi'soap are better 

 adapted to this purpose than others. Laundry soaps, for instance, 

 when used, at the necessary concentration, will not remain entirely in solu- 

 tion. They tend to form a thin jelly of rope-like consistency thruout 

 the liquid, even when agitated. This is not the case with certain grades 

 of sodium and potassium soaps manufactured from vegetable oils, 

 such as soja bean oil. When this soap is dissolved in hot water and 

 diluted to spray strength the solution does not gel, but remains in 

 solution even on cooling. It is important to use a soap which does 

 not gel in solution at spray strength, otherwise the spray solution ^''is 



Table I. Results Obtained With Various Types of Soaps in Solution When Used Against 



THE Japanese Beetle 



