Nov. 1, 1924 
Alternaria Leaf spot of Cauliflower 
437 
Under humid conditions the surface is 
soon covered with conidiophores bear¬ 
ing an abundance of spores. The 
conidiophores are short, olivaceous in 
color, usually concolorous with the 
spore, septate and branched. They 
are 5 to 7.5 m wide by about 35 to 45 m 
long. The spores are nearly linear 
to obclavate in shape and are borne on 
the conidiophores in chains, as many as 
8 to 10 in a chain being quite common. 
The spores are produced abundantly 
both in culture and on the host. They 
are olivaceous to brown in color and 
together with the conidiophores im¬ 
part the characteristic olivaceous color 
to the lesions on the host. They are 
smooth at first, becoming roughened 
tate 9-11.25X35.6-45 n; 7, septate 13- 
16.8X56.25-65 fx; 8, septate 11.25-16.8 
X 50-75 ix. The perfect stage of this 
fungus is unknown. 
Elliott (7) discusses what he terms 
secondary development in Alternaria 
spores. This was also noticed by the 
writer. In the young cultures the 
spores are regular and smooth with few 
vertical cross walls. As the spores 
grow older the constrictions at the 
septa become deeper, the cells round 
off, the spores become darker in color, 
and the walls become roughened. 
This variation of the spore size and 
character has led to considerable 
confusion in the determination of A. 
brassicae . 
Fig. 3.—Various types of spores of Alternaria brassicae. X 1,000. 
with age, and have as many as 10 hori¬ 
zontal septations but few vertical ones. 
Spores from old cultures often have 
more septations and are thicker in 
proportion to their length and more 
obclavate than those in fresh cultures 
or those from fresh lesions. Spores 
with more than six horizontal septa¬ 
tions are not numerous. Various spore 
types are shown in Figure 3. 
The spores taper somewhat toward 
the apex. The apical cell often is 
more or less rectangular in cross sec¬ 
tion, the outermost wall, however, 
being shorter than the wall contiguous 
with the penultimate cell. The basal 
cell is somewhat rounded. The maxi¬ 
mum and minimum measurements 
for spores with different numbers of 
septations taken both from culture and 
from the host are as follows: 1, septate 
6.5- 7.5X11-13 fx; 2, septate 7.5-9.5X 
18.5- 20.6 ix ; 3, septate 9-11.2X26- 
41.25 /*; 4, septate 9-11.25X39.5-45.5 
n; 5, septate 9-13.9X37.5-45 /*,* 6, sep- 
CONTROL OF THE DISEASE 
Alternaria leaf spot of cauliflower 
and cabbage is of comparatively little 
importance during most seasons, so 
that ordinarily no remedial measures 
are necessary. However, spraying 
with Bordeaux mixture 4-4-50 with a 
sticker added is recommended in case 
of a severe outbreak (16). 
The results of other workers seem 
to indicate that this disease may be 
held in check somewhat by treating 
the seed. Chupp ( 8 ) reports a 100 
per cent killing of Alternaria on the 
seeds of cabbage by treating them 
with hot water at 56° for 10 minutes. 
However, the fungus could still be iso¬ 
lated from seeds treated with mercuric 
chloride. He likewise states that 
Walker found that treating cabbage 
seed with hot water at 50° for 30 
minutes or 55° for 10 minutes will 
completely eliminate Alternaria. 
As stated above, the disease on cauli¬ 
flower plants growing in the field is not 
