florlda Agricullural Experiment Stallon.
CABBAGE BLACK ROT.
BY H. S. FAWCETT.
The disease of cabbage, known as "black rot," which js due to the
bacterium, Pseudomonas c'mpestris, has for several years caused serious
losses to the cabbage, cauliflower, and rutabaga crops of this State. It is
also a destructive disease in other parts of the United States where cab-
bages are grown in large quantities for the market. Scientific investigations
have brought out some practical ways of preventing the disease. These
preventive measures, in so far as they-ean be made applicable to Florida con-
ditions, are here given.
HOW TO PREVENT BLACK ROT:
SEED-BEDS-The seed-beds should be prepared in fresh soil, in which no
plants of the cabbage family (cabbage, rutabagas, cauliflowers, collards,
turnips, radishes, kale, mustard, etc.) have been growing. This is necessary
because the bacteria live from one season to another in decayed cabbages,
or old soil, and probably in some ordinary field weeds related to the cabbage.
SEEDS-The seeds should be treated before planting. Put them in a cloth
sack and lower the sack for fifteen minutes into a solution of corrosive
sublimate (one part to one thousand parts of water); then spread the seeds
out to dry, not allowing the direct rays of the sun to fall upon them. Do
not use a metal vessel, as this would be corroded. Corrosive sublimate tab-
lets may be bought from druggists, and one tablet is sufficient to treat a
pound of cabbage seed. This treatment of the seed will not injure its vitality.
Prof. F. C. Stewart, of the New York Experiment Station, has proved that
the bacteria causing black rot may remain alive on dry seed for as much
as eight to eleven months. He also found living bacteria of black rot on
seeds bought from reliable seedsmen. It is probable that the disease was
first brought into Florida vegetable fields on the seed.
PLANTING OUT-The plants should be set out, as far as possible, in ground
that has not been planted in cabbage, or closely related plants during the
previous season; and never in soil on which refuse plants related to the
cabbage have been allowed to rot.
FERTILIZING-The use of stable manure or compost should be avoided-
since such manures are known to cause fields to remain infected, by keep-
ing the bacteria alive from one season to another. The potash in the com-
mercial fertilizer should be slightly increased, as this will probably harden
the plants and make them less liable to an attack of the disease.
DESTROYING INFECTED PLANTS-As soon as any plants show the disease,
they should be taken out and destroyed at once. This is suggested because
PRESS BULLETIN No. 101.
October 24, 1908.
insects carry the disease from one plant to another, and it is probable that
the wind also distributes it over the fields by blowing dust from infected
plants to those that are still healthy.
CLEANING TOOLs-All tools and implements that have been used in infected
soil should be sterilized by wiping them with a dilute solution of crude car-
bolic acid, before using them in newly planted soil. At the very least, imple-
ments should be scoured bright before using them in the new field. The bac-
teria could easily be carried from an old field into the newly-set field on
soil that was allowed to remain on cultivators and other implements.
PREPARING FOR THE NEXT SEASON-As soon as the next crop is marketed
all refuse cabbage plants and old stubs that remain in the field, should be
completely destroyed, either by plowing under, or better, after removal from
the field. All plants of the cabbage family should also be prevented from
living over in the fields that are to be used for cabbages in the future.
ROTATION CROPs-The cleared field should be planted to crab grass, beg-
garweed, or velvet beans. These crops are not subject to the black rot
disease, and will keep the soil in good condition for the next year's crop
of vegetables, as well as help to starve out the black rot bacteria in the
The prevention of the disease, and its eradication from infected fields,
depend upon the strict following out of these eight points. The neglect of
any one point may be fatal to success. If, however, these lines of action
are followed, it may be expected that the loss from the disease will be
State papers please copy.