tobacco diseases and their management mina mila plant pathology april 11, 2011
TRANSCRIPT
Tobacco Diseases and Tobacco Diseases and their Managementtheir Management
Mina MilaPlant 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 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
0
2
4
6
8
10
12
14
16
4.5 5 5.5 6 6.5 7
Soil pH
Bla
ck s
han
k In
dex
Have a soil sample tested to determine nutrient and lime needs. Do not over lime!
Dukes & Apple, 1965
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
Crop Black Shank Granville WiltCorn High Mod.
Cotton High Mod.
Fescue High High
Peanuts High Low
Pepper High None
Potato, white High None
Small grain High High
Soybean High High
Sweetpotato High Mod.
Tomato High None
Rotation
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
Variety sequence
0
10
20
30
40
K326 NC71 K346 K346 K326
0
10
20
30
40
326always
71 always 346always
346-71 326-71
2000
NO RACE 1
2003
RACE 1
Duplin co.
BS
in
cid
ence
(%
)
Varieties and Races
Disease Index
Variety Race 1 Race 0
CC 27 25 0
K 326 30 17
K 346 10 4
NC 471 9 0
NC 71 20 5
NC 72 23 3
SP 168 13 1
SP 179 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 ControlSummary 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
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 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
Crop Black Shank Granville WiltCorn High Mod.
Cotton High Mod.
Fescue High High
Peanuts High Low
Pepper High None
Potato, white High None
Small grain High High
Soybean High High
Sweetpotato High Mod.
Tomato High None
Rotation:
Available fumigants
Material Rate/Acre
Method of
Application
Waiting
PeriodContro
lTelone C-17(1,3
d+chloropicrin)
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!!!!