'AGRICULTURAL RESEARCH CENTER
HASTINGS, FLORI OCT 2 9 1973
Mimeo Research Report PR-1973-3 October 173
1.F.A.". Univ. of Florida
RECOMMENDATIONS FOR REDUCING SPREAD OF BLAlif 'tr S
D. P. Ueingartner, Asst. Plant Pathologist (Asst. Prof.)
INTRODUCTION: 'Blackrot of cabbage remains to be the most important disease of
cabbage in Florida and probably the entire U. S. Blackrot is caused by a micro-
scopic bacterium called Xanthomonas campestris. The bacterium not only infects
cabbage, but also plants related to cabbage such as cauliflower, collards,
rutabaga, turnips, rape, black mustard, chinese cabbage and certain weeds.
Infected cabbage seeds or cabbage plants, other infected hosts, and infested
soil can harbor the bacteria. Blowing and splashing rains, irrigation water,
droplets of dew, moving machinery or other means of moving droplets of water
can spread the disease rapidly from plant to plant.
Recommendations in this report are based on the most recent information con-
cerning blackrot. It is important to note that sprays such as maneb + copper
and the antibiotics streptomycin sulfate and terramycin have not effectively
controlled the disease. Also, there are no documented reports of adjuvants
or spray additives controlling the disease.
1. Plant seedbeds on new land or land which has not been cropped to
crucifers (cauliflower, collards, mustard, turnips, broccoli, rutabaga,
brussels sprouts, or rape) for the past two years.
2. Plant seedbeds in an area removed (at least 1/4 mile) from production
fields where cabbage and other crucifers are being grown.
3. Plant only hot water treated (1220F for 25 minutes) seed. If non-hot
water treated seed is planted, it should be sown in separate seedbeds
isolated from those planted with hot water treated seed. Treat seed
with a fungicide such as thiram following hot water treatment.
4. Keep seedbeds weed-free, especially front wild mustard and other crucifers.
5. Spray seedbeds regularly with insecticides and fungicides. Insect
injury and disease can mask symptoms of blackrot. Spray after dew
has dried from plants.
6. Thoroughly inspect seedbeds for blackrot symptoms on a regular basis
(every 10-14 days) before pulling transplants. This is especially -::*'
critical 2-3 days before plants are lifted.
7. Do not mechanically top or chop plants before transplanting. This
practice can spread blackrot throughout the plant bed.
8. Use new crates or crates which have never been used for other cruci-
ferous crops such as collards, turnips, mustard, broccoli or cauli-
9. Do not use in seedbeds, the sane equipment used in production fields.
If this is not possible, thoroughly clean equipment, preferably with
steam, or at least by washing. Equipment should be dry before entering
10. Do not spray or dip transplants in water when they are lifted.
11. Avoid using contaminated drainage water for spraying or irrigating
plants. Drainage water in canals could carry bacteria front infested
fields. Use of such water in a black-rot-free field could infect
the healthy crop.
12. If blackrot is observed in a seedbed, under no circumstances attempt
to salvage healthy appearing plants from that seedbed.
II. Field Cabbage.
1. Use only transplants grown according to the seedbed practices listed
2. Move equipment through fields after dew has dried from foliage.
3. Wait at least 12-14 months before planting cabbage in fields which
have been infested with blackrot.
4. Some varieties (see Research Report PR-1973-2) are more tolerant to
blackrot than others. Consider planting tolerant varieties in fields
which have been infested with blackrot.
5. Maintain adequate drainage. If possible, plant lower sections of
the production area first. This will help keep blackrot bacteria
in drainage water flowing away from younger plants.
6. Avoid using contaminated drainage water for spraying or irrigating
plants. Drainage water in canals could carry bacteria from infested
fields. Use of such water in a black-rot-free field could infect the
7. If blackrot occurs:
a. Move equipment through fields as infrequently as possible.
b. Move equipment through infested fields only after foliage has
dried and work last those fields which are infested.
c. Use different equipment in infested fields from that used in
healthy fields. If this is not possible, thoroughly clean
equipment with steam. Allow equipment to dry before entering
d. Disk under infected cabbage as soon as possible.
e. Wait at least 12-14 months before planting cabbage in infested field,
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