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





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

RISK MODELS

http://wwwagwx.ca.uky.edu/plant_disease.html

RISK MODELS

http://wwwagwx.ca.uky.edu/plant_disease.html

RISK MODELS

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

QUESTIONS?

WWW.SL IDESHARE.NET/NICOLEWARDUK

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

[email protected]

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

Education

Fire Blight: Disease Management for Kentucky Apple Orchards