766 
Diseases 
Celery as grown in Michigan is not as 
susceptible to injury of fungus diseases 
as in many other sections of the country. 
The comparatively cool, moist days of the 
growing season are especially favorable 
for the production of healthy, vigorous 
plants, but in seasons that are unusually 
warm, these diseases often become very 
ruin entire 
injurious and sometimes 
crops. 
Damping-Off 
Rhizoctonia 
This is the most serious disease of the 
celery plants while in the seed bed. Dur- 
ing the first two weeks after the seedlings 
appear, it is especially apt to attack the 
plants. This disease causes a decay on 
the main stem or root just at the surface 
of the soil, which quickly kills the young 
seedling. During warm moist weather it 
is apt to be very injurious, spreading 
rapidly throughout the bed. In the green- 
house, too much heat, lack of ventila- 
tion, and watering the plants on dark 
cloudy days, or late in the afternoon, all 
tend to promote this disease. Thorough 
ventilation, plenty of light, judicious care 
in watering, in general, keeping the plants 
on the “dry side,” tend to prevent this 
disease. 
Early Celery Blight 
Cercospora apti 
A common disease of celery infecting 
the foliage early in the season. It first 
appears as well defined spots on the leaves 
that soon become so numerous as to cause 
the leaves to turn yellow and finally die. 
On the dead leaves the disease multi- 
plies very rapidly and soon spreads to the 
other plants. It does not generally ap- 
pear late in the season, but plants weak- 
ened by this disease are often afterwards 
attacked by the late blight. Spraying 
the plants with Bordeaux mixture, as 
recommended for the late blight will con- 
trol this disease, the early spraying be- 
ing especially important. 
Late Celery Blight 
Septoria petroselini 
Of the diseases affecting celery this is 
generally the most common and serious 
one. It first appears in late summer or 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
early fall as irregular rusty brown spots 
on the outside leaves, spreading under 
favorable conditions over the entire leaf 
surface and to other leaves of the plants, 
causing a burned appearance to the foli- 
age in a very short while. During un- 
usually warm, moist weather in the grow- 
ing season, or after the crop is stored, 
this disease proves very destructive. 
Plants set upon poorly drained land or 
plants stunted or weakened by any other 
means are especially susceptible to it. If 
the plants are kept growing vigorously 
and well cultivated they are not as sus- 
ceptible to it, and are generally able to 
withstand its effects. However, when the 
blight has become well established upon 
the plants it is then too late to apply ef- 
fective remedial measures. The disease 
may be prevented also by spraying the 
plants with Bordeaux mixture,* using the 
5-5-50 formula, or the ammoniacal car- 
bonate of copper spray, beginning when 
the plants are small, spraying once be- 
fore lifting them from the seed beds, and 
continuing the spraying every ten days 
or two weeks until the plants are ready 
to blanch by boards. The success of this 
work will depend largely upon the 
thoroughness with which the foliage of 
the plants is covered, as it is important 
that all portions of the plant be reached 
by this spray. All diseased plants and 
refuse left in the field after harvesting 
should be carried from the land, rather 
than to turn it under with its spores of 
this disease to cause another infection the 
following season. When conditions will 
permit, rotation of crops will prove very 
desirable, devoting the land to cabbages, 
onions, peppermint or some other suit- 
able crop for two or more years until 
the land is free of these spores. 
Insects Affecting the Celery Plant * 
The celery plant is by no means im- 
mune to insect attack. It is preyed on 
by many of the garden pests, army worms, 
cut worms, the zebra caterpillar, the cel- 
ery looper and by a number of other cater- 
pillars. Besides these are several suck- 
ing insects, plant lice, leaf hoppers, a 
techenammain 
* For details of spraying send to Michigan 
Experiment Station for bulletin on spraying. 
