148 Diseases of Greenhouse Crops 



outer leaves, or involve the whole head. Affected 

 stems become brittle and may be readily broken. At 

 first they are a blue green afterward becoming brown. 

 The disease is met with in the field, but may also be 

 introduced in the greenhouse. 



The Organism, Nellie Brown ^ has definitely 

 proved that Pseudomonas vitans is the cause of the 

 trouble which seems so prevalent in South Carolina. 

 The causal organism is a short rod with rounded 

 ends, motile by means of polar flagella (fig. 26, b.), 

 one at each end; produces no spores, but capsules 

 and pseudozoogloese. It liquefies gelatin slowly and 

 produces no gas. 



Control. The disease may be introduced with in- 

 fected seedlings or soil. For the latter, soil steriliza- 

 tion with steam or formaldehyde is recommended. 

 Diseased seedlings should be discarded. 



The Kansas Disease 



Caused by Pseudomonas marginale Br. 



Symptoms, The disease seems to appear when the 

 plants are half grown. At first the leaves wilt 

 slightly in restricted areas at the margin. On the 

 older leaves wilting starts at the tips. The affected 

 areas fall over and gradually dry up. The vascular 

 tissue then becomes affected and brown, then 

 reddish, and finally black. The tissue of the 

 dead parts on the leaves becomes dry and papery. 



♦Brown, Nellie A., U. S. Dept. of Agr., Jour. Agr. Research, 13: 

 367-388, 1918. 



