PRESS BULLETIN 221
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
CUCUMBER AND CANTALOUPE BLIGHT.
By 0. F. Burger
The cucumber and cantaloupe crops in Florida are attacked every year
by a disease known in different localities as Blight, Rust, or Fire Blight.
This blight causes greater or less loss to the grower, depending upon weath-
er conditions. The disease is favored by rains and cloudy weather. In sea-
sons of little rain and plenty of bright days the blight makes slow progress.
In the spring of 1913, the cucumber crop was badly attacked in the South-
ern part of the State. The season was exceptionally wet and cloudy, and
consequently the blight caused a heavy loss.
Symptoms of the Disease
The disease makes its first appearance in the field on the older leaves
at the center of the plant. Yellow angular spots bordered by veins will be
detected. These become more distinct, and if the weather is favorable
there appears underneath the spot a faint violet powder, which consists of
the spores of the fungus. The older leaves are always affected first, and the
young leaves at the tips remain green the longest.
The growers rarely make preparation to combat the disease until the
crop is badly affected, when it is too late. Spraying with Bordeaux mix-
ture is a good preventive, but is not a cure for the disease. It has been
shown that if the vines are sprayed thoroughly with Bordeaux mixture the
disease can be controlled. The spraying, however, must be commenced when
the plants are young, and be repeated every week or ten days. The first
spraying should be made when the plant has about four leaves. It is es-
sential to keep all the young leaves coated with the mixture. The copper
!n the spray is poisonous to the germinating spores of the fungus. It is nec-
March 7, 1914
essary, therefore, in order to keep the vines healthy, that the foliage should,
be kept covered with the mixture.
Spraying for Blight
A spraying experiment was carried on, in co-operation with a grower, for
the purpose of testing the efficiency of Bordeaux mixture in controlling
blight. On account of the delay in receiving the spraying machine, the work
was somewhat belated. But good results were obtained in spite of this.
Bordeaux mixture, (4-6-50) was used in this experiment. The machine was
one which had the pump geared to the wheels. The barrel held fifty gallons,
and the nozzles were so arranged that five rows could be sprayed at one
time. But on account of the inefficiency of the pump, only thirty gallons of
the spray were applied per acre. Not less than fifty gallons should be ap-
plied to an acre.
The sprayed rows kept a greener color during the season, and they yield-
cd more cucumbers than the unsprayed rows. Four applications were made
during the season, with a week or ten days between each spraying. The
cost of spraying was figured on the basis of four sprayings for 23 acres. The
cost of teams and labor was $28, and the material cost $35; making a total
The average price of encumbers being $1.50 per basket; the gross gain
by spraying on 23 acres was $300.50. Deducting the cost of spraying, which
was $63, and $25 for deterioration of the machine, the net gain on 23 acres
Cause of the Disease
Cucumber and cantaloupe blight is caused by a fungus known as Pseu-
doperonospora cubensis. The disease is spread by the spores, which are
borne on the under side of the leaf, and, as stated above, have in mass 'a
faint violet or smoky color. The spores fall on the upper side of the leaf,
germinate, and penetrate the epidermis. After the fungus enters the leaf,
it grows in the tissues and kills the cells. Finally the fungus again bears
its spores cn the under surface, and these are blown about by the wind to
start new infections.
State papers please copy.