S. DEPARTMENT OF AGRICULTURE 



Other plants are affected by brown root rot, notably the tomato. 

 Potatoes are affected to a lesser extent, as are many legumes. Little 

 is known relative to the importance of this disease in the culture of 

 other crops. In the case of tobacco culture in New England, how- 

 ever, it is to be ranked as one of the major maladies affecting the 

 crop. 



The experimental work reported in this bulletin has been mainly 

 conducted in the laboratories at the Wisconsin Agricultural Experi- 

 ment Station, using soils from the Connecticut Valley, but the field 

 plats were located in the Connecticut Valley. The results therefore 

 apply more specifically to the soils of that valley, although in prac- 

 tice the conclusions are believed to have a wide application in tobacco 

 culture. 



Fig. 1. — A field of Havana tobacco grown at Suflield, Conn., showing a crop which 

 is practically a failure, due largely to brown root rot. Note that some spots in 

 the field are less seriously affected 



SYMPTOMS OF BROWN ROOT ROT 



Brown root rot occurs both in the shade-grown and sun-grown 

 tobacco in the Connecticut Valley. Three varieties are here in- 

 volved — the shade-grown Cuban, the Havana Seed (Connecticut 

 Havana), and the Connecticut Broadleaf, the latter two varieties 

 being grown in the open field. The aboveground symptoms may 

 vary somewhat with the different varieties and conditions. The most 

 striking aboveground symptoms are the general stunting (fig. 1) 

 and the temporary wilting of the affected plants during periods of 

 high transpiration. The most striking cases of wilting have been 

 observed in the Havana variety grown in the open field (fig. 2), 

 although this may be equally common in the Broadleaf variety in 

 New England. The shade-grown tobacco is not ordinarily so subject 

 to wilting, apparentty on account of the reduced transpiration under 

 such cultural conditions. Under some conditions a gradual yellow- 

 ing and death of the lower leaves of the plant occur, particularly 

 during the late summer. The stunting, wilting, and yellowing are 

 also characteristic of the Thielavia root rot and may, of course, be 



