APPLE INSECTS 159 



a liberal use of tobacco dust. It was applied on a lO-year-oId 

 orchard by removing the earth to a depth of 4 inches and for a 

 distance of 2 feet around the trunk. Five or six pounds of the 

 dust were evenly scattered over this area and the dirt replaced. 

 Nursery trees were treated by putting the dust in trenches along- 

 side the rows. Further detailed experiments in Georgia ten 

 years later, however, gave very unsatisfactory results in or- 

 chards and nurseries with tobacco used in various forms in the 

 excavated areas or trenches. Some trees received over 12 

 pounds of the dust in four months, two applications being made. 

 Whale-oil soap was also used in these experiments even at the 

 rate of 2 pounds to a gallon without success ; and it was found 

 that carbon bisulphide injected into the ground would kill the 

 aphids only over a limited area near the application hole, and it 

 could not be used in sufficient quantities to kill all the aphids 

 without killing or injuring the trees. These Georgia experi- 

 ments demonstrated the value of an application of 15 per cent 

 kerosene emulsion (the stock emulsion formula diluted with 

 about 10 gallons of water). The soil was removed to a depth of 

 about 3 inches over an area from 1| to- 4 feet around the trees, 

 depending on the size of the trees, and after the application the 

 soil was replaced. Three gallons of the 15 per cent emulsion 

 on the smaller area and 6 gallons over the larger circles served 

 to saturate the soil for 2 to 4 inches, and it gradually permeated 

 the soil a foot or more, where a perceptible odor remained for 

 many weeks. All the aphids the emulsion reached were killed 

 and the kerosene odor acted as a repellent for a long time. The 

 cost per tree varied from 4 to 8 cents. A 10 per cent emulsion 

 (stock formula diluted with 17 gallons of water) was very 

 effective on nursery trees when poured in shallow trenches made 

 close to the trees along each side of the rows. This kerosene 

 emulsion treatment should be made during early summer and 

 not later than the last of July, as it may injure dormant trees 

 or those that have made most of their growth for the season. 



