but applied in this way they are likely, under certain weather condi- 

 tions, to be injurious to the kernel and to the young plant.^ 



15. While there is no evidence that the corn root-aphis thrives 

 hest on comparatively unthrifty plants, as do many other insects, it is 

 sure that the corn plant endures the drain of its infestation with less 

 injury when the soil is fertile and the corn well cared for. The good 

 corn-farmer on a good corn-farm will consequently suffer less from 

 this insect, as a rule, than his less careful and less fortunate neighbor. 



16. A fre(|uent rotation of crops, with a short period in corn, is 

 a most valuable measure of prevention against root-louse injury, since 

 corn following some other crop than corn can only become infested 

 by means of root-lice coming into it from outside fields. 



17. The more generally correct practices are followed in any 

 neighborhood the less will be the injury done by the root-aphis to 

 the fields even of those who pay no attention to it. On the other hand, 

 a general neglect of it will give it such opportunities of multiplication 

 that it will swarm out of infested fields in numbers to give its attacks 

 the character of an epidemic. It is consequently to the interest of 

 every one to do his best to establish the correct routine of corn culture 

 thrnout his neighborhood, as well as to follow it carefully himself. 



18. Finally, to prevent mistakes, the fact should be known that a 

 few other kinds of root-lice are likely to infest the roots of corn tem- 

 porarily, e\en when the crop is planted on ground not in corn the year 

 before. Certain grass root-lice and clover root-lice may live for a time 

 on corn, and may even do some injury in early spring, leaving the 

 fields, however, before the summer is over. 



Recent Articles in the Office Reports 



My latest articles on the corn root-aphis, giving the results of ex- 

 periments in detail, were published in 1908 and 1909 in my Thirteenth 

 and I'^ourteenth reports. The first of these articles gives an account 

 of several field experiments made in 1904 and 1905, with deep plowing 

 and repeated disking of infested fields as a preparation of the ground 

 for planting; and the second article describes a long series of experi- 

 ments made in 1905 and 1906. in the insectary and in the field, with 

 various repellent substances applied to the seed at planting with a 

 view to excluding the ants and the root-lice from the hills. 



'This statement concerning conditions under which seed-corn may be injured 

 by kerosene and other oils is based upon extensive and very careful experi- 

 ments made by Dr. J. H. Whitten when he was a graduate student in botany 

 at the University of IlHnois. The results of these experiments have now been 

 published by him in detail in the Bulletin of the Illinois State Laboratory of 

 Natural History. \"olume X. Article V. 



