1. Tobacco Diseases and their Management Mina Mila Plant Pathology April 11, 2011

2. 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

3. 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

4. Black shank

5. Phytophthora nicotianea

6. Black shank symptoms

7. 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

8. Black shank and pH Have a soil sample tested to determine nutrient and lime needs. Do not over lime! Dukes & Apple, 1965

9. Destroy tobacco roots and stalks

10. % BS Roots left in soil29 Roots plowed out20 Roots plowed out and cover crop planted 20 F. Todd, 1974

11. CropBlack ShankGranville Wilt CornHighMod. CottonHighMod. FescueHigh PeanutsHighLow PepperHighNone Potato, whiteHighNone Small grainHigh SoybeanHigh SweetpotatoHighMod. TomatoHighNone Rotation

12. % BSYield (lb/A) Tob-Tob-Tobacco262089 Soy-Tob-Tobacco152658 Soy-Soy-Tobacco52760 T. Melton, 1994

13. Black shank Control Use Resistant varieties Apply Ridomil Gold Use a Fumigant if: –Nematodes are a problem –Granville wilt is a problem

14. How resistance works? Partial resistance (PR) Race 0Race 1 High PR (K346) Low PR (K326)

15. How resistance works? complete resistance Race 0Race 1 : ph gene NC 71 SP 227

16. Black Shank Control-Varieties Bladen County, 2001

17. Race 0 Race 1 NC 71 Ph gene NC 71 Ph gene Black Shank

18. Variety sequence 2000 NO RACE 1 2003 RACE 1 Duplin co. BS incidence (%)

19. Varieties and Races Disease Index Variety Race 1Race 0 CC 27 250 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

20. 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

21. Black shank Control Summary of 31 tests (NCSU, Tobacco Extension, 1997-2007) Good control with: RG, preplant + 1 st cultivation + layby OR RG, 1 st cultivation + layby OR Fumigation + RG, 1 st cultivation

22. Forsyth County 2007 Time of RG application, 2007 Black shank, Race 1

23. 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

24. Granville wilt (Ralstonia solanacearum)

25. Granville wilt symptoms

26. 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

27. CropBlack ShankGranville Wilt CornHighMod. CottonHighMod. FescueHigh PeanutsHighLow PepperHighNone Potato, whiteHighNone Small grainHigh SoybeanHigh SweetpotatoHighMod. TomatoHighNone Rotation:

28. Available fumigants Material Rate/ Acre Method of Application Waiting PeriodControl Telone C-17(1,3 d+chloropicrin) 10½ galRow21 daysExcellent Chloropicrin 100 (chloropicrin) 3 gal““Excellent Pic +(chloropicrin 86%) 4 gal“““ Telone II (l,3-d)6 gal““Excellent

29. 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!!!!

30. 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