Family Cruciferae 203 



The diseased leaves become yellow and drop off 

 prematurely. The trouble apparently does not at- 

 tack the cauliflower head. The same disease may 

 also attack cabbage, but not radish, rutabaga turnip, 

 or mustard. 



The Organism. Pseudomonas maculicola is a 

 rod-shaped organism, with rounded ends, usually 

 forming long chains in certain media, but producing 

 no spores. The organism is actively motile by means 

 of polar flagella. Involution forms are produced in 

 alkaline beef bouillon; and pseudo-zooglceae occur 

 in acid beef bouillon. No gas is produced and the 

 organism is aerobic, and is killed by drying and 

 exposure to light. 



Control. Badly diseased plants should be pulled 

 up and destroyed. Spraying with 4-4-50 Bordeaux 

 is recommended. In spraying cauliflower with 

 copper compounds, and especially if the latter are 

 in a concentration somewhat stronger than the plant 

 can stand, numerous warts will appear on the leaves 

 in about three days after spraying. These warts 

 should not be mistaken for a disease induced by a 

 parasitic organism. The wart formation is appar- 

 ently due to a stimulation by the salts absorbed by the 

 host cells. Von Schrenk 1 found that warts on cauli- 

 flower leaves may be readily produced by spraying 

 them with a solution made up of 5 oz. copper car- 

 bonate dissolved in a mixture of three pints of am- 

 monia to fifty gallons of water. He further found 



1 Von Schrenk, H., Missouri Bot. Gard., 16th Ann. Rept. : 125, 

 1905- 



