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Managing Stewart’s wilt and common rust in sweet corn

Managing Stewart’s wilt and common rust in sweet corn. Jerald K. Pataky Department of Crop Sciences Professor of Plant Pathology University of Illinois. j-pataky@uiuc.edu www.sweetcorn.uiuc.edu. Stewart’s wilt. Erwinia stewartii. Seedling wilt phase. Symptoms following leaf veins.

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Managing Stewart’s wilt and common rust in sweet corn

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  1. Managing Stewart’s wilt and common rust in sweet corn Jerald K. Pataky Department of Crop Sciences Professor of Plant Pathology University of Illinois j-pataky@uiuc.edu www.sweetcorn.uiuc.edu

  2. Stewart’swilt Erwinia stewartii

  3. Seedling wilt phase

  4. Symptoms following leaf veins

  5. Ooze test

  6. bacterial ooze

  7. Corn flea beetle

  8. Flea beetle feeding

  9. Two important generations of flea beetles • overwintering generation • - peak numbers at first plantings • - decreases until ~ Memorial Day • second generation • - peaks between June 20 to July 10 • - size affected by weather ( larger when dry)

  10. Flea beetle winter survival Average daily air temperature Dec., Jan., Feb. > 32 F survive* 27 - 32 F % survive* < 27 F killed *size of previous population

  11. Ten Warmest Winters since 1895 10. 1930-1931 36.2 9. 1952-1953 36.2 8. 1999-2000 36.2 7. 1908-1909 36.3 6. 1998-1999 36.4 5. 1953-1954 36.8 4. 1920-1921 36.9 3. 1997-1998 36.9 2. 1991-1992 37.9 1. 1931-1932 40.0 Laura Sweets, University of Missouri, Columbia

  12. December 2000 16.7 F

  13. Will flea beetles survive 2001/2002? Average daily temperature Dec Jan Dec Jan Location01 0200 01 Janesville, WI31 28 12 21 Rockford, IL31 29 12 21 Mendota, IL32 2913 21 Urbana, IL35 34 17 26 Brownstown, IL37 35 21 29 Dixon Springs, IL41 38 28 34

  14. Control Stewart’s wilt • resistant hybrids • control flea beetles

  15. susceptible moderate resistant

  16. Scale for rating Stewart’s wilt

  17. Resistance to Stewart’s wilt • flea beetle feeding wounds • limit movement of E. stewartii

  18. moderately resistant moderately susceptible

  19. susceptible

  20. Informationon hybrid reactionsto Stewart’s wilt • Midwestern Vegetable • Variety Trial Report • www.sweetcorn.uiuc.edu • extension publications • literature from seed companies

  21. R S

  22. Effect of Stewart’s wilt on sweet corn yield • growth stage • level of resistance

  23. Stewart’s wilt and sweet corn yield effect of growth stage at time of infection Suparyono & Pataky, 1987

  24. Stewart’s wilt and yield effect of host reaction (resistant to susceptible) Freeman & Pataky, 2000

  25. Marketable ears and incidence of systemic infection

  26. Effects of Stewart’s wilt on yield Growth stage Hybrid 3- to 5- 5- to 7- 7- to 9- reaction leaf leaf leaf R 0% 0 % 0 % MR 0-30% 0 % 0 % MS 10-40% 0-20 % 0 % S 40-100% 15-35% 3-15% • prior to 3-leaf stage -- main stalk death

  27. systemic infection main stalk death

  28. Growing point is killed

  29. Tillers from main stalk death

  30. Stewart’s wilt and main stalk death Main stalk Hybrid Hybrid death (%) Rxn Bold 10% MR GH 2628 11% R/MR Bonus 11% R More 17% R/MR GH 2757 30% MS Empire 33% M/MS Jubilee 60% S July 1995, Manito, IL

  31. Controlling flea beetles Insecticides • seed treatments • in-furrow applications • foliar applications

  32. Seed treatment insecticides 60% to 80% control of Stewart’s wilt • imidacloprid (Gaucho) • thiamethoxam (Adage/Cruiser) • TI-435 - clothianidin

  33. Non-treated Treated Flea beetle feeding wounds

  34. Stewart’s wilt control on Jubilee

  35. Stewart’s wilt control on Jubilee

  36. Stewart’s wilt control on Jubilee

  37. Stewart’s wilt control on Jubilee

  38. treated non-treated

  39. Treated Non-treated

  40. imidacloprid

  41. Economic value of seed treatment insecticides Value = value of the crop ($/A) x incidence (%) x 0.7 (70% control) Example: Crop value estimated at $800/A x 5% systemic infection (w/o control) x 0.7 (70% control) = $28 / A estimated value of seed treatment

  42. Probability of 5% systemic infection in central Illinois Planted after 1 June 1998 to 2000 Hybrid reaction to Stewart’s wilt Incidence of systemic infection R (1-2) MR (3-4) M (5-6) MS (7-8) S (9) <5% 0.5 0.25 0.06 0 0 5-10% 0.31 0.31 0.19 0.13 0 >10% 0.19 0.44 0.75 0.87 1.0 1998 to 2000 represents worse case scenario

  43. Common rust Puccinia sorghi

  44. Effect of rust on sweet corn yield

  45. Rust severity is affected by: • abundance of urediniospores • host growth stage • weather • host resistance

  46. Urediniospores Teliospores

  47. Telia Uredinia

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