Tobacco Diseases and
their Management
Mina Mila
Plant Pathology
April 11, 2011
Disease Management
• What one does to keep the disease low
season after season
Disease Control
• What one does to keep the disease low
within a season
Diseases
Soilborne diseases; active in the soil for several
years
• Black shank
• Granville wilt
• Nematodes
Airborne disease; vector; weed; depends on
weather conditions
• Tomato spotted wilt virus
• Blue mold
• Target spot
Black shank
Phytophthora nicotianea
Black shank symptoms
Black Shank Management
•
•
•
•
•
Destroy tobacco roots and stalks
Rotate with non host crops
Improve drainage in poorly drained areas
PH (+6.0)
Avoid tobacco root wounding
Black shank and pH
16
14
Black shank Index
12
10
8
6
4
2
0
4.5
5
5.5
6
6.5
7
Soil pH
Dukes & Apple, 1965
Have a soil sample tested to determine nutrient and lime
needs. Do not over lime!
Destroy tobacco roots and stalks
Destroy tobacco roots and stalks
% BS
Roots left in soil
29
Roots plowed out
20
Roots plowed out and
cover crop planted
20
F. Todd, 1974
Rotation
Crop
Black Shank
Granville Wilt
Corn
Cotton
High
High
Mod.
Mod.
Fescue
Peanuts
Pepper
High
High
High
High
Low
None
Potato, white
Small grain
Soybean
Sweetpotato
High
High
High
High
None
High
High
Mod.
Tomato
High
None
Rotation
% BS
Yield (lb/A)
Tob-Tob-Tobacco
26
2089
Soy-Tob-Tobacco
15
2658
Soy-Soy-Tobacco
5
2760
T. Melton, 1994
Black shank Control
• Use Resistant varieties
• Apply Ridomil Gold
• Use a Fumigant if:
– Nematodes are a problem
– Granville wilt is a problem
How resistance works?
Partial resistance (PR)
High PR (K346)
Low PR (K326)
Race 0
Race 1
How resistance works?
complete resistance
NC 71
SP 227
Race 0
Race 1
: ph gene
Black Shank Control-Varieties
14
12
10
8
6
4
2
0
13.7
0.7
K
0.6
C
N
6
34
0.8
SP
71
er
ok
C
8
16
1
37
G
Bladen County, 2001
Black Shank
Race 0
Race 1
Variety sequence
40
30
2000
BS incidence (%)
20
NO RACE 1
10
0
K326
NC71
K346
K346
K326
40
30
2003
20
RACE 1
10
0
326
always
Duplin co.
71 always
346
always
346-71
326-71
Varieties and Races
Variety
CC 27
K 326
K 346
NC 471
NC 71
NC 72
SP 168
SP 179
Disease Index
Race 1
Race 0
25
0
30
17
10
4
9
0
20
5
23
3
13
1
35
1
Black shank Race 1
management & control
•
•
•
•
Destroy tobacco roots and stalks
Rotate
Apply Ridomil Gold (RG)
Use a Fumigant if:
– Nematodes are a problem
– Granville wilt is a problem
Black shank Control
Summary of 31 tests
(NCSU, Tobacco Extension, 1997-2007)
Good control with:
RG, preplant + 1st cultivation + layby
OR
RG, 1st cultivation + layby
OR
Fumigation + RG, 1st cultivation
Time of RG
application,
2007
Ridomil
Timing
Black shank, Race 1
3.6 e
pretran, 1stcult, Layby
47.1 ab
Layby, 3wksLayby
10.9 cde
1stcult, Layby
K 326
45.1 ab
Layby
64 a
Nontreated Control
0
Forsyth County 2007
20
40
Percent Disease
60
80
Variety x RG control
Select more than one varieties (i.e. some with
high yield and some with high resistance)
------------------------------------------------------------• A resistant cv. in hot fields
- Consider Ridomil application in “black
shank years”
• A moderate cv. in low to moderate pressure
fields with 2 Ridomil applications
Granville wilt
(Ralstonia solanacearum)
Granville wilt symptoms
Granville wilt
Management & Control
•
•
•
•
•
Destroy roots and stalks
Rotate
Avoid root wounding/Manage weeds
Use Resistant varieties
Use a Fumigant if:
– Nematodes are a problem
– Granville wilt is a problem
Rotation:
Crop
Black Shank
Granville Wilt
Corn
Cotton
High
High
Mod.
Mod.
Fescue
Peanuts
Pepper
Potato, white
High
High
High
High
High
Low
None
None
Small grain
Soybean
Sweetpotato
High
High
High
High
High
Mod.
Tomato
High
None
Available fumigants
Material
Telone C-17(1,3
d+chloropicrin)
Rate/
Acre
Method of Waiting
Application Period Control
10½ gal
Row
21 days
Excellent
Chloropicrin 100
(chloropicrin)
3 gal
“
“
Excellent
Pic +(chloropicrin
86%)
4 gal
“
“
“
Telone II (l,3-d)
6 gal
“
“
Excellent
Eliminate Fumigation to Save
Money ?????
• Chloropicrin is best bang for buck to control
Granville Wilt based on past pricing and testing
• Small yield benefits usually observed with
chloropicrin fumigation even where no disease is
noticed
• The best opportunities for eliminating fumigation
are in areas where no Granville wilt has
occurred
• LONGER ROTATIONS!!!!
Diseases
Soilborne diseases; active in the soil for several
years
• Black shank
• Granville wilt
• Nematodes
Airborne disease; vector; weed; depends on
weather conditions
• Tomato spotted wilt virus
• Blue mold
• Target spot