THE CORN ROOT-APHIS. H 



ing, but if warm weather follows the ants may reconstruct their nests 

 so that replowing will be necessary in the spring. In either case 

 the additional spring diskings are essential. 



Early 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, for the plowing disturbs the ant colonies, kills many of the 

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

 prevents the recolonization of ants and the growth of weeds. The 

 result is a significant reduction in the number of aphid eggs — eggs 

 being necessary to carry the insect over winter. 



REPELLENTS. 



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

 odorous substance offensive to the ants, which will prevent them from 

 colonizing the aphids on the cornroots or will drive them from the 

 treated field, may be used to advantage. This material does not 

 destroy either the ants or the aphids, but tends 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, 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 on the seed, as such treatment may injure it, 

 especially if the season be wet. Dilute one-fourth pound of oil of 

 tansy with 2 quarts of alcohol and 1 quart of water, or 2 pints of 

 asafetida with 1| gallons of water, and add either of these sub- 

 stances, thus diluted, to 100 pounds of bone meal, this amount being 

 sufficient for an acre. 



MAINTENANCE OF SOIL FERTILITY. 



The maintenance of soil fertility by the use of barnyard manure 

 or a commercial fertilizer has been recommended frequently, but is of 

 value only in assisting the plants to outgrow injury either by the 

 corn root-aphis or by any other insect which gi'adually affects the 

 plant. It does not limit the number of aphids or ants, directly or 

 indirectly, and can scarcely be included properly as a remedial or 

 preventive measure, for if the proper soil fertility were maintained 

 by cultivation and crop rotation excessive artificial fertilization 

 would seldom be necessary. 



COOPERATION AS AN IMPORTANT CONTROL MEASURE. 



One of the greatest difficulties in the control of insects injurious to 

 field crops is lack of community cooperation, and injury by the corn 

 root-aphis frequently may be traced directly to this cause. The 



