CONTROL OF ROOT FORM OF WOOLLY APHIS. 35 



A crew of three men was required — a driver, a man to operate the 

 filling and emptying of the tanks, and a man to distribute the water 

 evenly over the surface of the basin. 



One tank of 200 gallons was sufficient for the treatment of from 

 20 to 25 trees, and with a crew of three men it was possible to dispose 

 of one tank an hour, depending on the distance from the water supply. 



ADVANTAGES OF THIS METHOD. 



The advantages of this method are as follows: When properly agi- 

 tated every portion of the combination solution and the mechanical 

 mixture contains the same amount of carbon disulphid. When it is 

 poured onto the soil it sinks through the earth, carrying the carbon 

 disulphid to every part of the soil penetrated by the liquid. This 

 results in an even distribution and none of the aphids escape. With 

 this method no portion of the soil receives too much or too little of 

 the fumigant, but just enough to do the work. 



DISADVANTAGES OF THIS METHOD. 



The greatest disadvantage of this method is the amount of labor 

 in handling the large quantity of water required, the employment of 

 several horses and men being necessary for this purpose. 



The difficulty, when ordinary labor is employed, of preparing the 

 basins properly for the reception of the liquid, so as to insure an even 

 distribution of the liquid over the soil area to be treated, is a second 

 disadvantage. On hillsides it is almost impossible to insure the even 

 distribution of the liquid over the surface of the basin. 



On some trees, in some soils, the area of infested roots is so ex- 

 tended that treatment of a basin 4 or 5 feet in diameter will not reach 

 all the aphids, and since three-fourths gallon per square foot is re- 

 quired for success, the amount of water necessary for the treatment 

 of an area greater than the foregoing practically limits its use to small 

 trees with restricted root area. 



USE OF SODIUM CYANID IN SOLUTION. 



EXPERIMENTS ON VINES IN FRENCH VINEYARDS. 



Among the substances tried against the phylloxera in France was 

 sodium cyanid in solution. Bourcart 1 records the experiments of 

 Mouillefert as follows: 



The stocks were stripped to a depth of about 15 centimeters, with 

 a radius of 30 to 35 centimeters (12 to 14 inches), the soil being rather 

 dry. After pouring on the cyanid solution the soil was replaced at 

 the foot of the stocks and thoroughly packed. The dose varied from 

 20 to 25 grams per stock, dissolved in 10 liters (2.2 gallons) of water. 

 Wherever the solution had penetrated, the phylloxera and their eggs 



iBouRCAKT, E. Insecticides, fungicides, and weedkillers, p. 135. London, 1913. 



