44 
COLOKADO PIXPEKIMENT STATION 
CABBAGE 
Black-Rot (Pseudomonas campestris) (44) — Black-rot at present 
is not a serious disease in Colorado. In some sections of the United 
States it is one of the most destructive of cabbage diseases. Black- 
rot makes its first appearance along the edges of the outer leaves. 
Affected ai*eas wilt, turn yellow and dry up. The veins of the leaf 
become blackened. The disease spreads along the veins until it 
reaches the main stem from where it rapidly spreads to all parts 
of the plant producing the characteristic black rot. Frequently a 
plant may be affected one one side only in which case the affected 
side appears dwarfed. Much loss is often suffered in storage when 
slightly infected plants are stored. Infection may occur in seedling 
stage, killing the entire plant in a very short time. 
Black rot is a bacterial disease. The bacteria may gain en- 
trance to the plant through breathing pores or mechanical injuries, 
but they enter more commonly through the water pores along the 
margin of the leaves. The organism lives over the Avinter in the soil 
and decayed cabbage refuse and also on seed from diseased plants. 
Since infection may take place in the seed bed the plants should 
be closely Avatched to see that no infected plants are taken to the 
field. Crop rotation is necessary for effective control. Seed should 
be disinfected by soaking in corrosive sublimate solution (l-IOOO) 
for fifteen minutes or in formaldehyde (1-200) for tAventy minutes. 
Black-Leg (Phoma lignam) (44) — Black-leg is one of the most de- * 
structive of cabbage diseases. Often the greater portion of the crop 
may be destroyed. 
The disease is first noticed as irregular sunken spots Avith a 
purplish border on the stems near the surface of the ground. The 
spots increase in size until the stem is completely girdled. The 
plant is, of course, weakened and ultimately dies. Small black dots 
then appear all OA^er the surface of the diseased tissue. These are 
the spore cases or pycnidia containing the thousands of spores Avhich 
are set free to affect ncAv plants. 
Crop rotation and destruction of all infected plants are the 
most reliable control measures. Seed from diseased fields should 
never be planted unless thoroughly disinfected AAdth corrosive subli- 
mate. Seed should be planted in beds containing soil that has never 
grown cabbage before. 
YelloAvs (Fusarium conglutinans) (45) — The prevalence of this 
disease in Colorado is not knoAvn. It is one of the most imi)ortant in 
the states further east. 
