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

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

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

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

How resistance works? Partial resistance (PR)

Race 0 Race 1

High PR (K346)

Low PR (K326)

How resistance works? complete resistance

Race 0 Race 1

: ph gene

NC 71

SP 227

Black Shank Control-Varieties

13.7

0.7

0.6

0.8

0

2

4

6

8

10

12

14

Bladen County, 2001

Race 0Race 1

NC 71

Ph gene

NC 71Ph gene

Black Shank

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

Forsyth County 2007

Time of RG application, 2007Black shank, Race 1

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

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!!!!

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