Group Title: Circular (Florida Cooperative Extension Service) ;
Title: Black shank of flue cured tobacco
Full Citation
Permanent Link:
 Material Information
Title: Black shank of flue cured tobacco
Physical Description: 1 folded leaf : col. ill. ; 23 x 31 cm., folded to 23 x 10 cm.
Language: English
Creator: Whitty, E. B.
Mullin, R. S. ( Robert Spencer ), 1915-
Miller, C. R.
University of Florida -- Institute of Food and Agricultural Sciences. -- Agricultural Extension Service
Publisher: Florida Agricultural Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1968
Copyright Date: 1968
Subject: Flue-cured tobacco   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by E.B. Whitty, R.S. Mullin, and C.R. Miller in cooperation with Fred Clark and C.E. Dean.
General Note: Cover title.
General Note: "November 1968."
General Note: University of Florida Agricultural Extension Service circular 268
 Record Information
Bibliographic ID: UF00096114
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 51237166

Full Text


Vr 4 46

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Black shank of tobacco was first identified
in Florida in 1924 in the shade-grown tobacco
area around Quincy. It has per-
HISTORY sisted as a serious tobacco dis-
ease there. Discovered in the
flue-cured area near Winston-Salem, North
Carolina in 1931 and in South Carolina in
1948, outbreaks occurred in Georgia in 1959
and on several flue-cured tobacco farms in
Florida in 1961. By 1963, Black shank ap-
peared on some farms in every major tobac-
co-growing county in the state.
If not controlled, this disease could become
a major obstacle to successful production of
flue-cured tobacco in Florida.

Black shank is caused by the fungus,
Phytophthora parasitica var. nicotianae. The
disease almost always makes its
CAUSE first appearance in low areas of a
field. Once introduced into a field,
it is able to survive in the soil for a long

Once soil becomes contaminated, the fun-
gus may be spread in a number of ways.
From an infested plant-
DISSEMINATION bed, it can be carried to
the field on the plants.
When a field is infested, it can be spread by
equipment, on shoes, by wind and water
erosion or by any other means that results
in the transportation of soil particles from
one area to another. Where a pond or river
used for irrigation becomes contaminated
with fungus spores, the entire irrigated area
may become contaminated.

Wilting is the first symptom shown by
plants affected with black shank. Wilting
may occur while the plants are
SYMPTOMS small or not until the plants
are quite large, depending on

weather, severity of infection and other con-
dition. Since other organisms may also
cause tobacco to wilt, this symptom is not
sufficient to identify the disease.
In a black shank wilted plant, the large
lateral roots may be blackened and dead. As
the disease progresses, the leaves of the plant
die and turn brown, and the stalk becomes
black near the ground line. In advanced
stages, the pith will be wafered or separated
into discs in the darkened stem area. This
is a good diagnostic symptom for the identi-
fication of black shank. Once the fungus
gains entrance into a tobacco plant the dis-
ease may go up or down, affecting the entire
plant. Complete kill may occur within one
week after the first symptoms appear.

If a grower observes wilted plants in his
field, he should immediately contact the coun-
ty agent and get the condi-
PRECAUTION tion identified. If b lac k
AND shank is identified as the
PREVENTION trouble, take care not to car-
ry disease infested soil out of
the field on trucks, tractors or other equip-
ment, on tools or on the feet of men or ani-
mals. Plants or plant parts should not be re-
moved from infested areas. After the tobac-
co is harvested, a field infested with black
shank should be seeded to permanent pasture
and left for at least five years before being
cultivated again. Equipment should be kept
out of infested areas once it is seeded to
grass. These measures will not necessarily
eliminate the disease, but they will delay its
Every farm should follow a good crop rota-
tion system. A mixed rotation of several
crops is better than only two or three crops.
Legumes are not generally recommended in
tobacco rotation, due to disease problems and
the extra nitrogen they add to the soil. Avoid
crops such as tomatoes, pepper, eggplant and
Irish potatoes. These are hosts for many dis-
eases that affect tobacco, including black

Use of tobacco varieties resistant to black
shank should be considered once the disease
is found on a farm. It should be understood
that commercial black shank resistant varie-
ties presently available may not prove entire-
ly satisfactory under Florida conditions. In
North Carolina the following varieties carry
resistance and are used: McNair 20, Coker
80F, N. C. 95, Coker 111 and Coker 187.
Black shank can not be eliminated from an
area by growing a resistant variety, but by
following a good rotation and growing a resis-
tant variety, losses from the disease can be
held to a minimum.
Since black shank may be carried from the
planted to the field on seedlings, every far-
mer is urged to grow his own plants to help
prevent the spread of this disease. Fumiga-
tion with methyl bromide at recommended
dosage should be used to kill any spores that
might be in the plantbed soil.

Black shank is a severe disease of tobacco
that should be feared and respected. If wilt-
ing of tobacco occurs in a field,
SUMMARY call your county agent and have
the trouble identified as soon
as possible. Should your farm become in-
fested, switch to a variety of tobacco carry-
ing high resistance to this disease. Try to
prevent contamination of your farm by grow-
ing your own plants, practicing crop rotation
and keeping off contaminated farms.

This guide was prepared by S. L. Brothers, As-
sistant Agronomist and R. S. Mullin, Plant Patholo-
gist, in cooperation with Fred Clark, Agronomist,
Agricultural Experiment Stations, and C. E. Dean,
Assistant Agronomist, North Florida Experiment

(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida,
Florida State University and
United States Department of Agriculture, Cooperating
M. O. Watkins, Director

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