106 PAPERS ON CEREAL AND EORAGE INSECTS. 



Mayr, Lasius inter jectus Mayr, Myrmica scabrinodis Nyl., and Sole- 

 nopsis debilis Mayr. 



NATURAL CHECKS. 



There are no natural checks to the multiplication of the corn root- 

 aphis and its attendant ant except hard, beating rains that are long 

 continued. The thorough soaking of the ground by such rains 

 drowns out many of the aphides, and also the young of the ants. 



PREVENTIVE MEASURES. 



It happens that over the entire territory infested by the corn root- 

 aphis the best cultural methods for the growing of corn independent 

 of insect injury are just the methods that reduce the numbers of the 

 corn root-aphis and its attendant ant. These methods are crop 

 rotation, maintenance of soil fertility, arid early plowing, followed 

 by frequent cultivations. 



CROP ROTATION. 



The system of rotation that gives the shortest time in corn is the 

 best. In the cotton belt the injury from the root-aphis will be less 

 if cotton and corn are not allowed to follow each other in rotation. 

 Outside the corn belt it makes no difference what the rotation is from 

 the standpoint of root-aphis injury, because no other field crop is 

 injured by this insect. When an old cornfield is sown to some rota- 

 tion crop, such as one of the small grains, the ants are unable to 

 find food for the aphis except on the roots of weeds, which are soon 

 killed out by the attacks of the aphis, or are smothered by the grain. 

 Large numbers of the aphis will then acquire wings and leave the 

 field. There is some evidence that others are eaten by the ants, but, 

 one way or the other, the field is freed of them. 



MAINTENANCE OF SOIL FERTILITY. 



The maintenance of soil fertility by the direct application of ferti- 

 lizers does not lessen the numbers of the aphis, but by furnishing the 

 corn plant with sufficient food it enables it to make a strong growth 

 and mature a crop in spite of the aphis. This benefit is shown in 

 the illustrations (Plate V), from photographs taken by Mr. W. J. 

 Phillips at Kichmond, Inch 



EARLY PLOWING, FOLLOWED BY FREQUENT CULTIVATIONS. 



In order to reduce the numbers of the root-aphis old cornfields 

 in the Northern States should be plowed in the fall or early spring, 

 and then the ground should be stirred several times before planting, 

 with a corn cultivator or disk harrow. The burrows of the ants 

 infrequently go deeper into the ground than 6 inches, so that if the 

 ground is turned over and thoroughly stirred their nests are broken 



