Fire Blight: Disease Management for Kentucky Apple Orchards

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Fire Blight can be the most destructive disease of Kentucky orchards. This presentation describes the lifecycle of the bacterium Erwinia amylovora, as well as methods for disease management. For more information, spray guides, publications, and videos, see http://www2.ca.uky.edu/agcollege/plantpathology/people/ward.htm

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Fire Blight: Disease Management for Kentucky Apple Orchards

  1. 1. UNDERSTANDING AND MANAGING FIRE BLIGHT NICOLE WARD GAUTHIER, UK PLANT PATHOLOGY
  2. 2. WHAT IS FIRE BLIGHT? • Erwinia amylovora • Bacterium • Warm spring temperatures, high humidity or rain • Most common disease of apple • Most destructive disease of apple • Overwinters in dead wood, cankers • Manageable but tricky
  3. 3. LIFE CYCLE • Early spring • • • • • Activity at 45ᵒ 55ᵒ F to Optimal 65˚ to 70˚F 2 hours wetness Bacterial cells double every 20 min More wetness = more risk This is the first step in eliminating inoculum
  4. 4. LIFE CYCLE • Blossom Blight • Blossoms – first susceptible tissue • Early spring just as buds break – optimal conditions • Splashing rain and insects carry bacterium • Rapid death of blossoms, blighting and browning • Blighted flowers do not produce fruit
  5. 5. LIFE CYCLE • Blossom Blight • Infected blossoms serve as source of bacterium for subsequent shoot infections This is the first step in eliminating inoculum
  6. 6. LIFE CYCLE • Infection progresses downward • Cankers • Girdle twig, twigs die • Blighted leaves remain attached • Repeating infections • Temps 65ᵒ to 75ᵒ • Bacteria continue to multiply • Spread to other blossoms, especially rat tail blossoms
  7. 7. LIFE CYCLE • Shoot Blight - new, rapidly-growing shoots • Optimal conditions, humidity/wetness • More rain = more bacterial cells • Disseminated by rain and insects • Wilt from tip, develop crook • Risk highest with high numbers of bacterial cells
  8. 8. LIFE CYCLE • Trauma, hail • Under moderate temps, wet conditions • Damage increases susceptibility • Possible bacterial activity up to 90 ˚F
  9. 9. LIFE CYCLE • Fall infections • Cool, wet temps • Active growth (fall pruning, fertilization) • Overwinter • Dead wood • Cankers • Early spring, bacterial cells begin to multiply • Cycle continues
  10. 10. CULTURAL CONTROL • Sanitation – remove source of inoculum • Remove cankers and dead wood during dormant season • Prune cankers 6 to 12” below cankers or dead wood • Prune trees for air circulation to reduce humidity and promote rapid drying • Avoid rapid growth • Do not over-fertilize • Avoid aggressive pruning during growing season
  11. 11. CULTURAL CONTROL Pruning • Do not prune while pathogen is active • Remove dead and diseased wood during dormancy • Remove ALL sources of inoculum • Prune 6-8 inches below cankers • Remove and destroy pruned material • There are few circumstances that justify pruning during the growing season • Disinfest tools between cuts • Break versus cut, paint damaged wood for easy ID • Better yet, wait!
  12. 12. BACTERICIDES • Dormancy (late dormancy) • Copper sulfate/fixed copper • Bloom • Streptomycin, oxytetracycline • 4 to 5 day intervals, as risk increases • Regulaid activator if using captan, dodine, or sulfur in tank mix • Shoot growth • Apogee
  13. 13. CONSIDERATIONS • What is your Risk? • History – Is there history of fire blight? • Weather – Are conditions optimal? • Susceptibility – What cultivars are in your orchard? • Bactericides – they are required • Copper is a no-brainer • At least 2 applications required during bloom, every 4-5 days during high risk • Other considerations • Hail or storms • Rat-tail blooms
  14. 14. RISK MODELS http://wwwagwx.ca.uky.edu/plant_disease.html
  15. 15. RISK MODELS http://wwwagwx.ca.uky.edu/plant_disease.html
  16. 16. RISK MODELS
  17. 17. CONSIDERATIONS • What is your Risk? • History – Is there history of fire blight? • Weather – Are conditions optimal? • Susceptibility – What cultivars are in your orchard? • Bactericides – they are required • Copper is a no-brainer • At least 2 applications required during bloom, every 4-5 days during high risk • Other considerations • Hail or storms • Rat-tail blooms
  18. 18. QUESTIONS? WWW.SLIDESHARE.NET/NICOLEWARDUK
  19. 19. WE NEED YOUR HELP Testimonials – • Our funding (results in free services to growers) depends upon impact reports • 1 to 5 short sentences describing how our program (plant pathologist, diagnostic lab, educational program) helped you and/or your orchard • Use numbers whenever possible – acres, gallons, dollars, spray applications
  20. 20. Nicole Ward, Extension Specialist Department of Plant Pathology www.ca.uky.edu/agcollege/plantpathology/people/ward.htm nicole.ward@uky.edu 859-218-0720 office 859-797-3333 mobile/text Facebook: www.KYPlantDisease.com UK - Diseases of Fruit Crops, Ornamentals, & Forest Trees Twitter: @Nicole_WardUK Blogger: nicolewarduk.blogspot.com

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