482 
Journal of Agricultural Research voi. xxiii, No. 6 
El. and Ev. and more recently “wildfire” has become the accepted com¬ 
mon name for the disease caused by Bacterium tabacum Wolf and Foster. 
The leafspot diseases of tobacco naturally fall into three disease 
categories, as regards cause, namely, (1) those due to nonparasitic 
agents, (2) those due to fungi, and (3) those due to bacteria. It is prob¬ 
able that additional terms should not be added to the list of common 
names until a satisfactory basis of classification based on these categories 
is established. However, we have come to refer in the laboratory to the 
disease herein described as the “Wisconsin bacterial leafspot” disease, 
and this term may tentatively be preferable to the commonly used term 
“rust.” 
OTHER BACTERIAL LEAFSPOTS 
Although it is only within recent years that certain leafspots of tobacco 
have been definitely shown to be of bacterial origin, it is fairly certain 
that one or more have existed from the earliest days of tobacco culture 
in this country. The earliest treatises on tobacco culture refer to “rust” 
and “firing,” although in most cases it would be difficult to judge the 
nature of the causative agent from the descriptions of these diseases. 
Killebrew and Myrick (6) , 2 for instance, wrote as follows— 
another field fire, called “black fire,” which is totally different from the red field 
fire, is caused by excessive humidity and occurs only after continued rains of several 
days’ duration with hot weather. This black fire is much more to be dreaded than 
the brown rust or red field fire, for it attacks the plants while immature , involving 
all the leaves. Sometimes the disease will spread over a field in two or three days 
and ruin the crop, making black deadened spots as large as a silver dollar, but this 
rarely happens. 
This disease Was undoubtedly parasitic in nature, especially in view of 
the fact that these experienced observers separated it from other symp¬ 
toms probably of nonparasitic origin. It is also quite likely that this 
disease was one of the two tobacco leafspot diseases recently shown to 
be of bacterial origin in this country. 
Similarly the disease described in this paper as “Wisconsin leafspot” 
has probably existed in Wisconsin for 50 years or more along with other 
leafspots under the name of “rust,” but now referred to by some of the 
older growers as “old-fashioned rust,” on account of the fact that it has 
not been as prevalent in recent years as in the earlier days of the industry 
in this State. 
Apparently the first leafspot disease of tobacco attributed to bacteria 
was that of “la rouille blanche” (white rust) of France, ascribed by 
Delacroix (r) in 1905 to Bacillus maculicola. The description of this 
disease is not sufficient to afford adequate comparison with our American 
leafspots, but in any case the description given indicates that it is different 
from the Wisconsin bacterial leafspot. Honing (4) in 1914 described a 
rust occurring in Deli (Sumatra) which he showed to be due to a bacterial 
organism which he named Bacterium pseudozoogloeae. This disease 
was also known as “black rust,” although it evidently was not the “wild¬ 
fire” disease of America, since neither the description of the causal 
organism nor that of the symptoms of the disease correspond with that 
of wildfire. Honing’s disease corresponds more closely to that of the 
Wisconsin leafspot, although, as will be shown by later comparison, they 
differ in several respects. 
* Reference is made by number (italic) to “ Literature cited,” p. 492-493. 
