SB 

 818 

 C578 

 ENT 



O. 86. - . Issncrl May 6, 1907 



iiited States Department of Agriculture, 



BUREAU OF ENTOMOLOGY, 

 L. O. HOWARD, Entomologist and Chief of Bureau. 



THE CORN LEAF-APHIS AM) CORN ROOT-APHIS. 



By F. M. Webster, 

 In Charge of Cereal and Forage-Plant Insect InveMigations. 



The corn leiif-;iphi.s {Aphis maidlt< Fitch) and the corn root-aphis 

 {Ajjkls maidi-radicis Forbes) are together made the subjects of this 

 circular because both attack growing corn, because it has 3'et to be 

 clearly shown that there is no direct kindred connection between 

 them, though it is possible that they are distinct species, and because 

 this question of their identit}" or relationship presents itself to almost 

 ever}" observing farmer. 



The leaf-aphis does the farmer little direct injury. The root-aphis, 

 on the other hand, sucks the sap from the roots of his corn, thereby 

 causing the plants to become dwarfed, and in serious cases the leaves 

 turn brown and die. In an infested field the corn will be "spotted," 

 as farmers term it — that is, while the plants on certain areas in the 

 field may make a normal growth and may ear well later on, those 

 on other areas will make little growth, but tassel out after the}" have 

 become a foot or a foot and a half high, producing the almost worth- 

 less ears known as '•nubbins" or none at all. Thus the damage to 

 the crop in some fields at times reaches 50 per cent or more, and the 

 annual loss throughout the corn belt nmst amount to well on toward 

 a million dollars. This root-aphis is really becoming the most serious 

 of the many insect pests of the corntield, especially where a strict 

 system of crop rotation is not carried out. 



THE CORN LEAF-APHIS. 



The corn leaf-aphis (tigs. 1, 2) was described by Dr. Asa Fitch in 

 1856 from eastern New Yoik. but it is now known to occur from New 

 England to North Dakota and Texas, as well as on the Pacific coast. 

 Besides, it was found by the writer in great abundance on sorghum 

 on the grounds of the Agricultural College of South Australia, at 

 Roseworthy, February 9, 1889. Professor Lowrie, at that time prin- 

 cipal of the college, assured the writ(!r that it sometimes became so 

 excessively aV)undant as to render the plants obnoxious as fodder for 



30313— No. 86—07 



