38 BULLETIN 130, U. S. DEPARTMENT OF AGRICULTURE. 



For this latter purpose the following apparatus was devised: A series 

 of pinholes was made in the bottom of a pail and the latter then 

 filled with earth, well tamped down, and the soil scooped out slightly 

 and heaped up against the inside of the pail so as to furnish a minia- 

 ture basin for the reception of the liquid. The soil column thus 

 prepared was approximately 7 inches in depth. Into the basin on 

 the surface of this column was poured 10 per cent kerosene emulsion 

 at the rate of three-fourths gallon to the square foot of soil surface, 

 and a drip pan placed immediately beneath the pail in order to catch 

 the drippings from the soil column. The following conclusions were 

 arrived at as a result of this and several other similar experiments : 



A. The first inch of surface soil separates out and retains all the soap in the 



emulsion, together with sorne of the kerosene content. 



B. The first 4 inches of the soil retains almost all the remainder of the kerosene. 



C. The drippings from the soil column 4 inches in depth consist of clear 



water with a slight trace of kerosene. 



FIELD EXPERIMENTS. 



Experiments carried out in the field, in which 3-year-old apple 

 trees infested with the woolly aphis were used, corroborated the 

 results obtained in the laboratory. The basins for the reception of 

 the kerosene emulsion were prepared as outlined for the apphcation 

 of carbon disulphid in water, and the material was used at the rate 

 of three-fourths gallon per square foot of soil treated. The majority 

 of the aphids within 8 inches of the surface were killed as a result of 

 the treatment, but those at lower levels escaped. Furthermore, the 

 trees were very severely injured as a result of the apphcation of the 

 emulsion. The following spring, seven months after the treatment, 

 the foliage presented a weak, yellowish appearance, and practically 

 no new growth. The rootlets were badly injured and were not 

 replaced that season by new growth. 



The mechanical and unstable character of kerosene emulsion, 

 together with the cost and labor required in preparing the quantity 

 necessary for soil treatment, renders this method of little value. 



DEEP PLANTING, 



Theories have been advanced from time to time in the literature to 

 the effect that by planting the apple tree deeper in the soil than is 

 normally done the aphis infestation will be prevented. Evidently it 

 is presumed that the aphids will be unable to live at the lower depths 

 in the soil occupied by the root systems of these deeply planted trees. 

 Furthermore, it is taken for granted that the root systems will grow 

 normally at these depths. 



The writer fortunately was enabled to make observations and photo- 

 graphs of the effects of deep planting, as carried out by a grower at 



