In the first article^ it was shown that after the usual plowing and 

 harrowing as a preparation for corn, disking three times additional 

 and harrowing once had the effect to reduce the number of root-lice 

 on the experimental plots 92 per cent, and the number of hills in- 

 fested by root-lice 82 per cent; and to reduce the number of ants 92 

 per cent and the number of hills infested by ants 64 per cent. It was 

 further siiown that twice disking reduced the number of root-lice 84 

 per cent and the number of hills infested by them 7}) per cent, the num- 

 ber of ants 65 per cent and the number of hills infested by them 59 

 per cent; and that once disking reduced the root-lice and hills infested 

 by them 43 per cent and 41 per cent, and the ants and hills infested by 

 them 42 per cent and liZ per cent, respectively. All these ratios were 

 determined in each case by comparison with check plots in the same 

 fields which had received only the usual preparation for corn. 



These facts, taken by themselves, seem thoroly conclusive and 

 highly satisfactory. Nevertheless, since corn root-lice, like most in- 

 jurious insects, are largely affected by the varying conditions of 

 weather, soil, and crop, it was thought necessary to test these conclu- 

 sions by repeating and varying the above experiments in a way to ar- 

 rive at maximum, minimum, and average benefits under the varying 

 phases and prjictices of Illinois agriculture. It i? a part of the purpose 

 of this article to give the product of these later experimental studies 

 in detail. 



The second article above referred to.' that published in my Four- 

 teenth Report, dealt especially with the effects of the treatment of seed- 

 corn with oil of lemon, carbolic acid, formalin, and pure kerosene, 

 with the general result that under the conditions of 1906, where seed- 

 corn was treated with oil of lemon just l)efore planting in infested 

 fields, the yield was increased by 1,159 ear-bearing stalks to the acre, 

 while a similar treatment of the seed with carbolic acid increased the 

 vield by 945 such stalks, a formalin treatment by 742, and a kerosene 

 treatment by 274.^ 



Notwithstanding this surprisingly favorable result, there was som« 

 appearance of injury to the seed by all these substances. The check- 

 plot contained more living hills to the 80-rod row than any of the ex- 

 perimental plots, the difference being small, however, except in the 



^Field Experiments on the Corn Root-aphis (Aphis niaidiradicis Forbes). 

 24th Rep. State Ent. 111., pp. 8-29. See especially the table on p. 29. 



'Experiments with Repellents against the Corn Root-aphis. 1905 and 1906. 

 25th Rep. State Ent. III., pp. 1-26. 



'25th Rep. State Ent. 111., p. 21. 



