306 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



from the general line of remedial work against subterranean insects. 

 This departure is soil fumigation and, inasmuch as we have only tried 

 one fumigant, soil fumigation with sodium cyanide. 



Three phases of any remedial measure always confront the investi- 

 gator; first, will the remedy in question be efficient; second, will it be 

 practicable and safe; and third, will it be economical. The work of 

 the past season, which will be reviewed in detail later and which was 

 carried on under the Office of Cereal and Forage Crop Insect Investi- 

 gations of the National Bureau, proved the first of these phases affirma- 

 tively. The practicability of the treatment resolves itself into two 

 questions, how shall we apply the fumigant, and when shall we apply 

 it. The first question is being investigated by consultation with com- 

 mercial chemists and manufacturers of farm machinery. The second 

 question was partly solved by pot and field experiments this season. 

 Four possible and practicable times of application present themselves; 

 first, with the fertilizer at the time of seeding; second, drilling in with 

 an attachment at the time of corn cultivation; third, at the time of 

 fall ploughing; and fourth, at the time of spring ploughing. 



The great danger attached to the use of cyanide on the farm, both 

 to men and live stock, is, perhaps, the most serious negative factor 

 that the initial work has faced and may ultimately render the treat- 

 ment inadvisable. 



Another serious factor in determining the final value of this remedial 

 measure is its ultimate effect upon the microbiota of the soil. Recent 

 botanical investigations have proved the interdependence of certain 

 plants, notably the Leguminosce, and certain bacteria. Investigators 

 have also found other free living nitrifying bacteria in the soil and now 

 believe that the fertility of the soil is largely dependent upon the 

 activities of mJcroorganisms. If the cyanide destroys these beneficial 

 and necessary bacteria, reinoculation will be necessary after the cya- 

 nide treatment. However, that this absolute soil sterilization would be 

 undesirable, is not as evident as it might seem on casual consideration. 

 From the statements of Russel and Hutchinson of the Rothamstead 

 Experiment Station (England) quoted by Prof. T. B. Wood in his 

 presidential address before the Agricultural Section of the British 

 Association for the Advancement of Science at Birmingham this year, 

 the so-called soil toxicity, held to be caused by toxic substances pro- 

 duced by the crops themselves, is in reality not a soil toxicity but a 

 soil impoverishment. The soil is depleted of its nitrifying bacteria 

 by certain protozoa which feed upon these bacteria. These undesir- 

 able protozoa Avould be killed as well as their prey and reinoculation 

 would be more than compensated by the vigorous development of the 

 newlj^ introduced bacteria in the absence of their depredators. 



