30 BULLETIN 730, U. S. DEPARTMENT OF AGRICULTURE. 



advantages claimed for the method are that it is harmless to the vine, 

 even in full vegetation, and that by its use a uniform distribution of 

 the carbon disulphid in the soil is effected. It is stated, however, 

 that the disadvantages of this treatment are the enormous amount of 

 water required and the high labor cost. 



No record has been found of the use of this method in the United 

 States. 



EXPERIMENTAL WORK WITH THIS METHOD. 



Realizing the possible merits of this method of applying carbon 

 disulphid, a series of determinative experiments was carried out 

 during the seasons of 1914 and 1915. The resulting data, herewith 

 presented, include an account of the preliminary work to determine 

 the factors influencing this water treatment and a report of the large- 

 scale operations in the field in which this method was utilized, based 

 on the knowledge acquired in the preliminary experiments. In 

 conclusion, a discussion of the advantages and disadvantages of the 

 treatment is given. 



Preliminary Experiments. 



preparation op the basin. 



In applying quantities of liquid for the control of soil-inhabiting 

 insects, such as the root form of the woolly apple aphis, it is necessary, 

 in order that the material may be effective, to prepare a basin around 

 the base of the tree for the reception of this liquid in order that it may 

 be spread evenly over the soil surface, and to insure permeation and 

 absorption by the soil. 



In preparation for the reception of the carbon-disulphid solution 

 the basin should be made as shallow as possible, to prevent exposure 

 of the roots. If the roots are exposed, the gas in solution is prevented 

 from acting upon the aphids thereon, and- the treatment is thereby 

 rendered incomplete. The bottom of the basin should be absolutely 

 level, with the soil heaped up around the edges to confine the liquid 

 to the area undergoing treatment. 



In order to simplify the placing of the liquid, strips of galvanized 

 iron, shown in Plates VI and VII, were utilized. These strips were 12 

 feet in length and 5 inches in width, providing for a circular basin 4 

 feet in diameter. After leveling the ground about the base of the 

 tree one of the strips of galvanized iron was placed with the ends 

 overlapping 3 or 4 inches (PI. VI) and the dirt heaped up around the 

 outer edges. This gave a level basin for the reception of the liquid 

 and confined it to the area to be treated. 



