45 



nematodes, and this led us to make more extensive trials of the 

 steam heating method. While our experiments upon sterilizing' 

 the soil were well under way there appeared Bulletin No. 73 of the 

 Ohio Station' which gave some account of sterilizing the soil for 

 the nematodes on cucumbers. It appears from this bulletin that 

 Mr. Lodder, a practical cucumber grower in Ohio, who had experi- 

 enced severe losses from nematodes reported favorable results from 

 the use of steam. In looking up the matter further we also found 

 that a Mr. W. N. Rudd'^ had earlier emplo3'ed a method similar to 

 that described above with favorable results. More recently Mr. 

 J. N. May'*, a large rose grower, has described a method which he has 

 used extensively for sterilizing his soils to rid them of nematode 

 worms. Mr. May's heating is done on a large scale and it would 

 appear to be a practical method of treating nematodes even when 

 carried on in connection with a large range of houses. Our own 

 experiments along this line have demonstrated that as far as green- 

 house culture is concerned the method of sterilizing the soil by means 

 of steam for the purpose of ridding it of nematodes is at the present 

 time the most practical method which can be employed, although it 

 is not at all improbable that some other cheaper method may yet be 

 found. 



Amount of Heat Necessary to Kill Nematodes and Their Eggs. 



From the account given by Mr. May it would appear that consid- 

 erable heat is required to kill nematodes in the soil. He states that 

 "by the best authorities it is proven that nothing short of 225° F. 

 will kill them (nematodes) when protected in the soil, but to make 

 sure work 235° F. of heat is necessary". In regard to this state- 

 ment we shall have to take some exceptions and will subsequently 

 show that such temperatures are unnecessary to kill nematodes except 

 under exceptional conditions. 



It is well known that a temperature of 212*^ F. will kill any organ- 

 ism in a short time and in fact the great majority of organisms are 

 killed at much lower temperatures. Again the resistance of animals 



1 Note. While the term sterilizing has been employed by all writers who have described 

 their experiments upon steaming soil, it must be borne in mind that probably in every 

 instance complete sterilization has not been accomplished. We made cultures of soil which 

 had been heated up to 204 F. and in every instance bacteria were abundant. 



2 Ohio Agricultural Experiment Station, Bulletin No. 73, p. 227, 1896. By A. D. Selby. 



3 American Florist, \'ol. IX, p. 171, 1S94. 



4 American Florist, Vol. XIII, Feb., 1S9S. 



