Black leg, caused by the fungus Phoma lingam, affects cabbage. It has a worldwide distribution where cabbage is grown. Symptoms include brown lesions on stems that girdle the stem. The disease is favored by wet weather and spreads via spores dispersed by splashing water. Management strategies include controlling susceptible weeds, delaying spring plantings to avoid spore release periods, rotating crops, and fungicide applications.

1. COLLEGE OF AGRICULTURAL TECHNOLOGY
Affiliated to Tamil Nadu Agricultural University, Coimbatore
Kullapuram, Via Vaigai dam, Theni-625 562
BLACK LEG OF CABBAGE
STUDENT COURSE TEACHER
Mr. RAHUL. C Dr. PARTHASARATHY. S
ID. No. 2015021101 Asst. Prof., (Plant Pathology)

2. CABBAGE
Black leg: Phoma lingam/
Leptosphaeria maculans
Cornell university

3. DISTRIBUTION
• It has a cosmopolitan distribution and is known from
many countries.
• Where cruciferous crops are grown in Europe, Asia,
Africa, Australia, North, Central and South America.

4. SYMPTOMS
• Slight lesions on stems at cotyledon scars which
elongate, turn brown with a black to purplish border,
and become sunken.
• The lesion extends up and down the stem, the stem
becomes girdled and blackened, with many fruiting
bodies (pycnidia) embedded in the tissue.
• Lesions may extend below the soil and attack roots.

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6. PATHOGEN CHARACTER
• Spores are colorless and unicellular.
• The pycnidia are black and depressed in the
tissues of the host.
• Phoma is arbitrarily limited to those species in
which the spores are less than 15 µm as the
larger spored forms have been placed in the
genus Macrophoma

7. SYSTEMATIC POSITION
• PHYLUM : Ascomycota
• CLASS : Dothidiomycetes
• ORDER : Pleosporales
• FAMILY : Didymellaceae
• GENUS : Phoma
• SPECIES : P. lingam

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9. FAVOURABLE CONDITIONS
• Phoma lingam can survive for up to four years in
seed and three years in infected crop debris.
• The pathogen infects seedlings, forms pycnidia, and
produces abundant amounts of spores which exude
from the pycnidia in long coils and are splashed to
nearby plants to initiate new infections.
• The disease is favored by wet, rainy weather.

10. MODE OF SPREAD AND SURVIVAL
• Primary spread: Pycnidiospores
• Pycnidiospores are dispersed by splashing rain
or irrigation water, so pycnidiospore
movement is limited to relatively short
distances.
• Black leg can also move with infected
seed, Leptosphaeria can survive for years in
association with seed.

11. SYMPTOMS
• Presence of chlorotic or yellowish blotches,
initially roundish to angular where they are
limited by veins, on the upper surface of
leaves.
• On the lower surface, white creamy pustules
produced corresponding upper surface yellow
discolouration.
• Complete yellowing and premature shedding
of leaves.

12. PATHOGEN CHARACTER
• The fungus survives on living plants as
pycnidia, which produce water-splashed
pycnidiospores, or with plant debris as
pycnidia and pseudothecia.
• Pseudothecia release ascospores that may be
windborne long distances, at least several
miles and perhaps further on storm fronts.

13. • In spring-sown crops, pseudothecia do not form on
dead portions until after harvest, and their production
on residues atop the soil typically starts the following
fall after a couple of wet periods.
• Ascospores are released from the pseudothecia
following wet or humid conditions and when mean
temperatures are between 46°F and 59°F.
• Conditions conducive for ascospore production and
release commonly occur during the fall, winter, and
springtime

14. MANAGEMENT
• Control of all susceptible weeds (including tansy
mustard, hedge mustard, penny-cress, Birds rape
mustard, western yellow cress, wild turnip, and wild
radish) and volunteer Brassica and radish.
• If possible, delay spring plantings to avoid periods
of ascospore release; intermittent rains promote
release.

15. • Do not plant in or adjacent to a site where
black leg has occurred within the last 3 to 4
years; plantings within ¼ mile of a field
containing black leg-infected residues are at
high risk for black leg.
• Regular spraying with Mancozeb 0.25 %
effectively controls the disease.
• Controlled watering - avoid night irrigations if
possible.