WILT-DISEASES OF TOBACCO. 227 



in spots from which diseased tobacco had just been pulled out. In field tests in a bad year 

 (1909) on ground where all the untreated tobacco died, 50 per cent of a crop was made, 

 using 4 to 5 grams in each plant hole. The next year the loss was slight on 8 treated fields, 

 while on the neighboring untreated parts it was 50 to 60 per cent. 



Permanganate of potash will not penetrate the heavier soil and preference is given the 

 chloride of lime, although it is recognized that in its use there may be danger of injuring 

 the burning quality of the tobacco. 



Honing found great carelessness on the part of the planters in the disposal of diseased 

 plants. In many instances they have thrown the rotting tobacco plants into wells from 

 which afterwards they took water to put on the fields. (For abstracts of more recent 

 papers by Honing see p. 244.) 



THE NORTH AMERICAN DISEASE. 



Synonyms. North Carolina tobacco wilt; Granville tobacco wilt; Florida wilt. 



HISTORY. 



In September 1903, Stevens and Sackett, then of North Carolina Experiment Station, 

 distributed a well-illustrated, brief paper, describing a disease of tobacco which had caused 

 a good deal of injury in Granville County, North Carolina, and attributed the same to a 

 schizomycete. The Dutch papers are not mentioned and were probably unknown to them. 

 This disease is stated to be "so destructive that its spread throughout the country would 

 imply annihilation of the industry of tobacco growing." The bulletin devoted itself prin- 

 cipally to stating the fact of the presence of the disease, furnishing figures of it from good 

 photographs, and giving a brief description of the signs, together with some field observa- 

 tions on its prevalence and supposed manner of spread. The root was believed to be the 

 original seat of infection. The organism was not described or named, nor were any proofs 

 furnished that the disease was really due to bacteria, other than the strongly presumptive 

 evidence offered by the microscopic examinations. 



The same month (September) and a little in advance of the above publication, Dr. 

 R. E. B. McKenney, of the Bureau of Plant Industry, U. S. Department of Agriculture, 

 who had been engaged for some time in a study of tobacco diseases in cooperation with the 

 Bureau of Soils, but not under the writer's direction, published a brief circular describing 

 and illustrating this North Carolina disease. Dr. McKenney studied the disease in the 

 same localities as Stevens and Sackett. His circular states that the disease is due to a 

 fungus (Fusarium) closely related to that described by Erwin F. Smith as the cause of a 

 wilt in watermelons, cowpeas, and cotton. The publication of Dr. McKenney's circular 

 appears to have been premature, since he never obtained any proofs from inoculation that 

 this disease was due to a Fusarium, and the writer was never able to obtain from him any 

 slides or other material showing the presence of the fungus in the affected plants. From 

 Professor Stevens the writer obtained alcoholic material, both of root and leaf, which in 

 section showed the vessels and surrounding tissues to be plugged with bacteria, but wherein 

 no fungi could be demonstrated microscopically (figs. 116, 117). The writer also, in abun- 

 dant material since received directly from the diseased fields, has seen nothing of any disease 

 attributable to Fusarium. 



Further studies must be made to determine whether the Fusarium seen by McKenney 

 occurred as a saprophyte or a parasite and also to determine its morphology and cultural 

 characters. 



One of the writer's second set of inoculated plants (fig. 118) was destroyed in the 

 hothouse under the combined action of bacteria and Fusarium, but this is the only case 



