plot treated with kerosene, the hills in which numbered only 82.5 per 

 cent of those in the check. 



The whole operation of this year was regarded as provisional 

 only, and, in the language of my report, its conclusions were "taken as 

 applying exactly only to similar, if not identical, conditions — a similar 

 soil similarly prepared, equally infested with the corn root-aphis, and 

 subject to similar weather conditions — and with a treatment of seed 

 identical with ours in all particulars, including materials of the same 

 quality and strength. How far the results here described may be ex- 

 pected to apply to a different soil, less heavily, or even much more 

 heavily, infested, more thoroly prepared, and planted during either 

 a very wet spring or a very dry one, with a less perfect seed, treated 

 with slightly dift'erent chemicals and compounds, can be learned only 

 by repeated and varied experiment."^ As will be seen from later 

 studies described in this paper, this cautionary remark has been jus- 

 tified by the fact that no equally favorable result has been obtained 

 since 1906. 



List of Operations here Reported 



1907 



1. Field experiments with repellents, near Leroy, McLean county, 

 in charge of E. O. G. Kelly and J. J. Davis. 



2. Field experiments with repellents by the Bloomington Canning 

 Company, near Normal, McLean county, reported by J. A. West. 



3. Laboratory experiments made l)y J. J. Davis with the effect 

 on seed-corn produced by ordinary lemon oil, by lemon oil from which 

 the terpenes liad been extracted, and hy the terpenes themselves. 



1908 



4. Field experiments near (ialesburg, Knox county, supervised by 

 J. A. West, but in immediate charge of G. E. Sanders. In these ex- 

 periments various repellents were applied to the seed, and the soil was 

 variously prepared for planting by plowing to different depths, by 

 disking different numbers of times, and by plowing in fall and spring. 

 A comparison was also made of infestation and injuries bv root-lice 

 to a plot of corn on old oats-ground and to corn on old corn-ground. 



1909 



5. Field experiments near Bloomington, McLean county, in joint 

 charge of G. E. Sanders and W. P. Flint. This was essentially an ex- 



' 25th Rep. State Ent. 111., p. 22. 



