VI 



TOBACCO 155 



a number of serious outbreaks of this disease in the 

 United States, and Dr. E. F. Smith says that "if it 

 continues at its present rate of progress, tobacco-growing 

 in the infected districts will become impossible within 

 a few years, and if it should extend to all the tobacco- 

 growing sections of the United States this industry will 

 be destroyed." The disease has also been reported from 

 Sumatra by Hunger, from Cuba by Home, and may 

 exist in other places, not only on the tobacco but upon 

 related plants. 



The foliage of the diseased plants (Figs. 64, 65) wilts, 

 the veins darken, and longitudinal dark stripes are 

 formed on the stems. The fibro-vascular bundles of 

 the stems and leaves are stained brown and contain an 

 enormous number of Bacterium solanacearum, E. F. 

 Smith, which is the cause of the disease. The organisms 

 will live in the soil for many years and will also attack 

 potatoes, tomatoes, egg plants, and peppers, and related 

 plants, causing the characteristic wilt just described. 



The most common method of infection is no doubt 

 through wounds in the roots, arid it is greatly facilitated 

 by the nematodes. When soil becomes infected with 

 the disease it should not be used for any Solanaceous 

 crop for many years. Prevent the infection of clean 

 districts by not bringing seed, tools, or soil from infected 

 areas. If the outbreak is slight, burn all the infected 

 plants, and disinfect the soil if possible. 



Curing -house Troubles. The curing -house troubles 

 vary somewhat in different countries. They are usually, 

 if not always, due to the action of certain fungi and 

 bacteria, which reach their highest development in those 

 countries where the climatic conditions are favourable. 

 This class of diseases is not well understood, but among 

 the most important is the stem rot which is due to 

 Botrytis longibrachiata, Oud., which causes white 

 velvet-like mould on the stems and veins of the leaves, 

 and finally a decay of these affected parts and drying 

 of the other parts. The fungus matures and pro- 

 duces spores on this decayed material, which should be 



