260 Diseases of Economic Plants 



These troubles can largely be controlled by proper regula- 

 tion of the moisture and temperature conditions, ?. e., by 

 building such barns that outside air, when too damp, can be 

 excluded, and yet with proper provision for ventilation to 

 carry off the moisture from the drying tobacco. 



Wet-butts is due to freezing before curing is complete; 

 White- vein to rapid drying; Black-rot (Sterigmatocystis 

 nigra v. Tieg.) occurs during the sweating, the tobacco turn- 

 ing black and losing its proper texture. It is brought about 

 by too high moisture content. 



TOMATO.^'^ ^^^ 



Bacterial Wilt, blight (Pseudomonas solanacearum (EFS.) ). 

 — This disease of the tomato is widespread, especially in the 

 South, and prohibits tomato culture upon many thousands of 

 acres of land. It occurs especially in the states south of 

 Maryland, and has also been noted in New Jersey, Delaware, 

 Ohio, and Colorado. 



The leaves wilt, either singly or throughout the entire 

 plant at once; growth stops and the plant dies. The stem 

 appears at first dirty green, then brown, then black. It soon 

 shrivels, and the veins become brown and show as narrow 

 black lines, or in section as black dots. The wilting of the 

 foliage and the blackening of the vascular bundles are dis- 

 tinctively characteristic. 



Soil bearing diseased plants one season remains infested 

 during succeeding years and must be abandoned for tomato 

 culture. The disease is spread from plant to plant largely 

 by the potato bug (Colorado beetle) and other insects. 

 For this reason all leaf-infecting insects should be given 

 special attention. In other respects this disease in symp- 

 toms, cause, dissemination, and treatment is similar to 

 the usual soil diseases. 



Another wilt, similar but of slower development, is de- 

 scribed as caused by Bacterium michiganense EFS.^"*' 



Wilt ^^^ {Fusarium lycopersici Sacc. and Fusarium sps). — 

 This wilt is also widespread. It occurs not infrequently 



