674 
Symptoms 
The most characteristic symptom of this 
disease is the blackening and decay of 
the stem close to the surface of the 
ground. (Fig. 1.) Cankered areas are 
produced which sometimes completely 
girdle the stem and the plant is often 
broken over by the wind. The outer 
leaves of affected plants are bluish red 
in color, a characteristic which remains 
until the plant dies. Plants may be at- 
tacked at any time in their growth, more 
often, however, when they are about one- 
half grown. 
Other symptoms are spots on stem and 
leaves, in which numerous very small 
black specks can be seen. A wilting, in 
which the leaves droop instead of falling 
off, is frequently observed in diseased 
plants. 
Cause 
The fungus which causes black leg of 
cabbage and cauliflower is known techni- 
Ore Exp Ste 
Fig. 1. Black Leg of Cabbage. The stem is 
often girdled near the surface of the ground. 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
cally as Phoma oleracea. It enters the 
plant at some place near the surface of 
the ground, probably in wounds made by 
insects. Leaf infection may also take 
place. From these infected spots the 
fungus spreads, killing the plant tissues 
and shutting off the food supply from 
other parts. It comes to the surface to 
form the pycnidia or small black specks 
in which great numbers of minute spores 
are produced. These spores are forced to 
the surface and are carried by wind, 
water, insects or other agencies, to start 
new infection. Many seedlings are in- 
fected at planting time. If an occasional 
diseased seedling is handled, spores will 
be transmitted to the hands and later to 
healthy plants. The disease is frequently 
found closely associated with the wounds 
and injuries of insects, though infection 
may take place without aid from this 
source. 
Treatment 
The black leg organism is doubtless car- 
ried over in the stems and leaves of old 
decaying plants. It is a fungus capable 
of living in the soil, but one that can be 
controlled if the proper measures are con- 
stantly employed. The greatest care 
should be taken to keep the seed bed free 
from it, thus making certain that it does 
not become distributed over the fields. 
The recommendation is made in Ohio 
that the seed beds be sprinkled with 4-4-50 
Bordeaux at the time of planting, using 
one gallon of the mixture to each 10 
square feet. This operation should be re- 
peated two weeks before transplanting 
and again just before transplanting. This 
method has proven effective in holding 
the disease in check. It is better to select 
clean ground for the seed bed each year 
and disinfect the seed to be used. A safe 
treatment for cabbage and cauliflower 
seed is to use a solution of formalin, one- 
fourth pint in seven gallons of water, 
allow them to soak for 15 minutes, rinse 
in clean water and spread out to dry. 
When the disease appears in the field 
the affected plants should be removed and 
burned. 
The truck growers of the Northwest 
may well be on the lookout for this dis- 
