4 BULLETIN 562, U. S. DEPARTMENT OF AGRICULTURE. 



lion lying near the bark. This discoloration appears as longitudinal 

 streaks in this portion of the root, just as it does in the corresponding 

 part of the stalk. In the early stages of the disease only a few 

 of the roots are attacked, but eventually the whole root system is 

 involved. 



There are other diseases of tobacco involving decay of the stalk, 

 especially the so-called sore-shin, or sore-shank, which have been mis- 

 taken for the wilt, but the presence of a characteristic slimy ooze 

 when the stalk is cut and the black streaks in the woody portion are 

 usually sufficient to distinguish the wilt from other diseases. In 

 typical sore-shin, moreover, the stalk rots near the base, causing the 

 plant to topple over. 



CAUSE OF THE DISEASE AND ITS PRESENT DISTRIBUTION. 



Tobacco wilt is caused by Bacterium solanacearum E. F. S. This 

 is a well-known organism, first studied by Dr. Erwin F. Smith (6), 

 which causes a destructive rot of the tomato and Irish potato and 

 attacks many other plants besides these and tobacco. In infected 

 tobacco plants the bacteria soon become so abundant in the woody 

 vessels that these become plugged, thus cutting off the water supply 

 of the leaves, thereby causing them to wilt. If only the vessels on 

 one side of the plant first become clogged, then only the leaves on 

 that side of the plant will at first wilt. Xaturally, with the water 

 supply cut off, no further development of the leaves is possible and 

 the plant must soon die. Various theories as to the cause of tobacco 

 wilt have been put forward by farmers, and it has been believed by 

 many that the fertilizers used on the tobacco crop have been re- 

 sponsible in some way for the appearance of the disease. It is true 

 that fertilizers, cultural methods, weather conditions, and the like 

 may influence the extent of progress of the disease, but, as already in- 

 dicated, there is no doubt whatever that the disease is due to a specific 

 parasite. 



As has been stated, tobacco wilt, though designated by other names, 

 lias long been known in Sumatra and Java and in Japan. In this 

 country it was first found in Granville County. X. C, but about 10 

 years ago it made its appearance in the cigar-tobacco district of 

 Gadsden County, Fla.. and Decatur County, Ga., probably having 

 been introduced there through tobacco stems used as fertilizer which 

 came from the wilt district of North Carolina. For a number of 

 years the disease in Granville County was confined to the southern 

 portion of the county lying between the Tar and Neuse Rivers. This 

 happens to be the section enjoying the reputation of producing the 

 finest flue-cured tobacco grown in this country. Within this area 



