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



be relied upon in all cases to sterilize these materials. Finally, 

 tobacco growers are advised to practice rotation of crops on their 

 tobacco lands as a means of preventing the wilt, for if the soil is 

 exposed to infestation the disease is less likely to become established 

 when a systematic rotation of crops is followed. 



SUMMARY. 



In this country, tobacco wilt was first reported from Granville 

 County, X. C, in 1903. Subsequent investigation has shown that the 

 same disease, designated by other names, was already known in 

 Sumatra and Java and in Japan. Tobacco wilt is an exceedingly 

 destructive disease, causing the plant to die outright and frequently 

 resulting in a practically complete failure of the crop. 



The wilt produces definite symptoms in the leaves, the stalk, and 

 the roots of the tobacco plant. The more prominent features are a 

 characteristic umbrellalike drooping of the leaves, the presence of a 

 yellowish to black discoloration in the woody portion of the stalk 

 (showing as streaks when the bark is stripped off), the presence of 

 a slimy ooze when the stalk is cut across with a knife, and a decided 

 decay of the root system. 



Tobacco wilt is caused by Bacterium solanacearum E. F. S., which 

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

 attacks many other plants. The organism enters the plant through 

 the root and eventually brings about a plugging of the vessels, thus 

 cutting off the water supply from the leaves and causing them to wilt 

 and perish. Fertilizers, cultural methods, weather conditions, and 

 the like may influence the extent or progress of the disease, and it 

 has been observed that it is decidedly more destructive in relatively 

 wet seasons. 



For a time the wilt was confined to the southern portion of Gran- 

 ville County, X. C, but it has since spread into the adjoining coun- 

 ties of Vance, Durham, Wake, and Franklin and also has been found 

 in Ashe, Guilford, Greene, Chatham, Davidson, and Yadkin Coun- 

 ties, X. C. The wilt also has become established in the cigar-tobacco 

 district of western Florida and southern Georgia. 



In efforts to find a tobacco resistant to wilt, numerous species and 

 varieties, both wild and cultivated, from various parts of the world 

 have been tested, but no species or variety has been found which is 

 sufficiently resistant to meet practical requirements. The Sumatra 

 and certain crosses of Sumatra with Connecticut cigar types were 

 found to be relatively more resistant than the other forms tested. 



Experiments have been carried on for several years to determine 

 whether the wilt could be controlled by chemical or physical treat- 

 ment of the soil. Various acids, alkalis, and neutral salts, including 

 fertilizer materials, were applied to the soil by varying methods and 



