HOW TO DETECT OUTBREAKS OF INSECTS AND SAVE GRAIN. 21 



and aphid colonies can become reestablished, and also to prevent the 

 growth of weeds upon which the aphids live, making it necessary 

 for the ants to carry the surviving aphids to new fields. If infested 

 fields are to be replanted to corn, plow them to a depth of 6| or 7 

 inches in the spring after March 15. Follow this with three or four 

 diskings to a depth of 1 or 5 inches with a 16 or 20 inch disk, the 

 number of diskings and the intervals between them varying accord- 

 ing to the length of the period between plowing and planting. When 

 it is necessary to replant early injured corn, plow the field deeply 

 and thoroughly and then give three or four deep diskings at intervals 

 of two or three days. These practices necessarily involve additional 

 labor, but they prevent root-aphis injury and also put the field in 

 much better physical condition. Plowing in the fall before the ant 

 colonies go below the plow line is sometimes as useful as spring 

 plowing, but if warm weather follows, the ants may reconstruct their 

 nests and reassemble the aphids so that replowing in spring will be 

 necessary ; but whether the field be plowed in the fall or the spring, 

 the spring diskings are essential. 



Earh^ fall plowing, followed by frequent deep diskings in fields 

 damaged by the root aphis that season, is a good practice from the 

 standpoint of community control as well as for the personal benefit 

 derived, because the plowing disturbs the ant colonies, kills many of 

 the aphids, and destroys the weeds upon which they live, and disking 

 prevents the recolonization of ants and prevents the growth of weeds, 

 resulting in a significant reduction in the number of aphid eggs to 

 carry the insect through the winter. 



REPELLENTS FOR THE CORN-ROOT APHIS. 



Where it is impossible to practice one of the foregoing measures, 

 repellents may be used to advantage. The object is to repel the ants 

 by the use of an odorous substance offensive to them, thus preventing 

 them from colonizing the aphids on the corn roots or driving them 

 from the treated field. These materials destroy neither the ants nor 

 the aphids but tend to drive away the ants, the presence of which is 

 essential to the life of the aphids. Oil of tansy, tincture of asafetida, 

 oil of sassafras, anise oil. kerosene, and oil of lemon are useful for 

 this purpose, one of these materials being mixed with a chemical 

 fertilizer, such as bone meal, and applied by means of a planter 

 equipped with a fertilizer attachment. They should not be applied 

 directly to the seed, as such treatment may injure it, especially if 

 the season be wet. One-fourth of a pound of oil of tansy should be 

 diluted with -2 quarts of alcohol and 1 quart of water, 2 pints of 

 asafetida should be diluted with 1J gallons of water, and either 

 repellent thus diluted should be added to 100 pounds of bone meal, 

 this amount being sufficient for an acre. 



