152 



suitable soil conditions. The liquid is best applied by pi-eparing 

 shallow basins about the tree and should be used only when the soil 

 is in a moist condition. The solution is best prepared by pouring 

 the carbon bisulphide into the water and agitating vigorously. The 

 carbon bisulphide thereby breaks up into small globules, some going 

 into solution and the remainder forming a mechanical mixture with 

 the solution. The gas diffuses laterally and vertically only as far as 

 the liquid penetrates, and therefore every square foot of infested soil 

 must be subjected to the action of the solution in order to insure 

 complete control. When used at the foregoing rate the carbon 

 bisulphide produced no iuimy to the roots of apple. The treatment 

 may be made at any time during the growing season except during 

 the period of 2 or 3 weeks in the spring when the trees are budding. 



In orchard practice the solution is best applied by using a power 

 spraying outfit and two auxiliary tanks. 



The advantages of this method are, firstly, the even diffusion of 

 the liquid and complete Aphid mortality in the soil area treated and, 

 secondly, the safety with which the bisulphide can be used. The 

 disadvantages of the method are, firstly, the huge amounts of water 

 required, with consequent high cost of labour ; secondly, the difficulty, 

 on any but level ground, of preparing basins with level floors, thus 

 insuring the proper distribution of the liquid over the area to be 

 treated ; and thirdly, the wide area of infested roots on older trees, 

 every square foot of which must be treated with the liquid. This 

 last condition precludes the use of carbon bisulphide except on small 

 trees with restricted root areas. 



Sodium cyanide at the rate of ^ oz. to 4 U.S. gals, water did not 

 kill the Aphids in the lower-soil depths, even when a superabundance of 

 solution per square foot was employed. No injury to apple roots 

 resulted when the material was used at this strength. The 

 only advantage this chemical possesses, as compared with carbon 

 bisulphide, is its ready solubility in water. On the other hand, its 

 uncertainty in producing Aphid mortality in the lower soil levels, to- 

 gether with its extremely poisonous nature, precludes its use in practice. 



When kerosene emulsion is applied to the soil it disintegrates into 

 its component parts ; the first inch of surface soil retains the soap 

 and some of the kerosene content ; the next 4 inches of the soil retains 

 almost all the remainder of the kerosene. Kerosene emulsion, there- 

 fore, does not kill the Aphids in the lower soil levels and the cost of 

 preparing the quantity necessary for soil treatment renders it of Httle 

 value. The application of this material to apple roots, in the writer's 

 experience, results in severe injury to the tree. 



Deep planting will not prevent woolly aphis infestation and results 

 in the death of many trees so planted, owing apparently to the inability 

 of the root systems to function properly under these conditions. 



Amari (S.). Sanji, Sanyo, Sanga ni kiseisuru Dani Pediculoides ni 

 kwansuru Konkyu. Dai ni Ho. [Studies on the Mite, Pediculoides, 

 parasitic on the Silkworm, Pupa and Moth. Part Il.]~Sangyo 

 Shikenio Hokoku [Report of the Sericultural Experiment Station\ 

 Tokyo, iii, no. 6, 16th September 1918, pp. 339-370, 1 map. 



The fact that the serious disease of silkworms commonly called 

 " mite-disease " is due to infestation by the females of a species of 



