Fire Blight: Disease Management for Kentucky Apple Orchards
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Transcript of Fire Blight: Disease Management for Kentucky Apple Orchards
N I C O L E W A R D G A U T H I E R , U K P L A N T P A T H O L O G Y
UNDERSTANDING AND MANAGINGFIRE BLIGHT
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
LIFE CYCLE
• Early spring
• Activity at 45 too 55ᵒ F
• 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
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
LIFE CYCLE
• Blossom Blight
• Infected blossoms serve as source of bacterium for subsequent
shoot infections
This is the first step in
eliminating inoculum
This is the first step in
eliminating inoculum
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
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
LIFE CYCLE
• Trauma, hail
• Under
moderate
temps, wet
conditions
• Damage increases
susceptibility
• Possible
bacterial
activity up to
90 ˚F
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
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
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!
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
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
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
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
Nicole Ward, Extension Specialist
Department of Plant Pathologywww.ca.uky.edu/agcollege/plantpathology/people/ward.htm
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