RECENT ILLINOIS WORK ON THE CORN 



ROOT-APHIS AND THE CONTROL 



OF ITS INJURIES 



By STEPHEN A. FORBES, State Entomologist 



The corn root-aphis, or corn root-louse, as it is more commonly 

 called, is now the most generally injurious insect pest of the corn field 

 in Illinois. Its injuries have been but little checked by all that has been 

 done and printed concerning it, and they are evidently increasing slow^- 

 ly in total effect. There is, in fact, no other corn-field insect which is 

 so frequently called to the attention of the economic entomologist. 

 Nevertheless, the corn-root-aphis problem has been practically solved 

 — not, perhaps, in the best way possible, or as completely as will be the 

 case when time, money, and skilled assistance are all available for fur- 

 ther studies and experiments. Undoubtedly, however, if the results 

 which have already been established were generally put to use in the 

 practice of the Illinois farmer, this aphis would presently lose its place 

 at the head of the list of insects affecting corn, and would l)e classed 

 among those which are only occasionally injurious enough to call for 

 special notice. 



It is the purpose of this article to set forth the results of our more 

 recent investigations and experiments (1907-1910) in all necessary de- 

 tail, and to show what they signify and how they apply to the routine 

 of corn culture in this state. 



The key to the control of this insect is to be found in its spring 

 condition in old corn fields which have been infested by it the year 

 preceding; and in the fact that corn is the only crop-plant upon which 

 it lives and multiplies. This is substantially shown by the following 

 facts. 



1. The eggs left by the corn root-lice in fall when the insects 

 themselves perish, are virtually all in the earth in corn fields. They 

 are collected there by the corn-field ant, which keeps them in its tm- 

 derground burrows until they hatch the following April and May. 



2. As the young root-lice escape from the egg they are placed by 

 these ants on the roots of pigeon-grass, smartweed, and other corn- 

 field weeds, on which they live by sucking the sap, giving off at the 

 same time an abundant f^uid excrement which is lapped up by the 

 ants as food. 



3. The root-lice hatching from the egg are all females, and pro- 

 duce no eggs, but bring forth living young when they themselves are 



