W. R. StevensonW. R. Stevenson
University of Wisconsin - Madison, University of Wisconsin - Madison, Department of Plant PathologyDepartment of Plant Pathology
W. R. Stevenson, UW-Madison
Why Do We Worry About Late Blight In A Seed Area ?
Why Do We Worry About Late Blight In A Seed Area ?
Seed potatoes are generally grown in cooler climates Seed potatoes are generally grown in cooler climates more favorable for late blight developmentmore favorable for late blight development
Late blight pathogen is wind borne, long distancesLate blight pathogen is wind borne, long distances
Late blight pathogen is tuber-borneLate blight pathogen is tuber-borne
Late blight is a community diseaseLate blight is a community disease
Seed potatoes are generally grown in cooler climates Seed potatoes are generally grown in cooler climates more favorable for late blight developmentmore favorable for late blight development
Late blight pathogen is wind borne, long distancesLate blight pathogen is wind borne, long distances
Late blight pathogen is tuber-borneLate blight pathogen is tuber-borne
Late blight is a community diseaseLate blight is a community disease
W. R. Stevenson, UW-Madison
Concerned customer baseConcerned customer base
Possible loss of crop certificationPossible loss of crop certification
Cost of disease controlCost of disease control
• $50 per acre $50 per acre $250 per acre $250 per acre
"Triple bottom line" "Triple bottom line"
• financial viability financial viability
• environmental responsibility environmental responsibility
• responsibility to society responsibility to society
Concerned customer baseConcerned customer base
Possible loss of crop certificationPossible loss of crop certification
Cost of disease controlCost of disease control
• $50 per acre $50 per acre $250 per acre $250 per acre
"Triple bottom line" "Triple bottom line"
• financial viability financial viability
• environmental responsibility environmental responsibility
• responsibility to society responsibility to society
Why Do We Worry About Late Blight In A Seed Area ?
Why Do We Worry About Late Blight In A Seed Area ?
W. R. Stevenson, UW-Madison
Pathogen arrives in seed area via wind or seedPathogen arrives in seed area via wind or seed Infection of susceptible, unprotected plantsInfection of susceptible, unprotected plants
• Before adequate fungicide programsBefore adequate fungicide programs
• Poor or no fungicide coveragePoor or no fungicide coverage Long wet and cool periodLong wet and cool period Disease spreads rapidlyDisease spreads rapidly Control costs escalateControl costs escalate Tuber infectionTuber infection Pathogen survives winter on tubersPathogen survives winter on tubers Repeat the cycleRepeat the cycle
Pathogen arrives in seed area via wind or seedPathogen arrives in seed area via wind or seed Infection of susceptible, unprotected plantsInfection of susceptible, unprotected plants
• Before adequate fungicide programsBefore adequate fungicide programs
• Poor or no fungicide coveragePoor or no fungicide coverage Long wet and cool periodLong wet and cool period Disease spreads rapidlyDisease spreads rapidly Control costs escalateControl costs escalate Tuber infectionTuber infection Pathogen survives winter on tubersPathogen survives winter on tubers Repeat the cycleRepeat the cycle
The Late Blight CycleThe Late Blight Cycle
W. R. Stevenson, UW-Madison
Tougher seed standardsTougher seed standardsCurrently allow 1% seed infection Currently allow 1% seed infection Some states force growers to plant only certified Some states force growers to plant only certified
seedseedRejection of seed lots when late blight on foliageRejection of seed lots when late blight on foliageWould a field be rejected for 1? 10? 100? 1000? Would a field be rejected for 1? 10? 100? 1000?
lesions per field??lesions per field??Can we predict tuber infection on basis of foliage Can we predict tuber infection on basis of foliage
infection??infection??
Tougher seed standardsTougher seed standardsCurrently allow 1% seed infection Currently allow 1% seed infection Some states force growers to plant only certified Some states force growers to plant only certified
seedseedRejection of seed lots when late blight on foliageRejection of seed lots when late blight on foliageWould a field be rejected for 1? 10? 100? 1000? Would a field be rejected for 1? 10? 100? 1000?
lesions per field??lesions per field??Can we predict tuber infection on basis of foliage Can we predict tuber infection on basis of foliage
infection??infection??
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
• 1% seedpiece infection1% seedpiece infection
• 10 ft-diameter area killed from 1 infected 10 ft-diameter area killed from 1 infected seedpieceseedpiece
10 foot diameter10 foot diameter
Potato Late BlightA Little Inoculum Goes a Long Way
Potato Late BlightA Little Inoculum Goes a Long Way
W. R. Stevenson, UW-Madison
Potato Late BlightA Little Inoculum Goes a Long Way
Potato Late BlightA Little Inoculum Goes a Long Way
• 1% seedpiece infection1% seedpiece infection• 10 ft-diameter area killed from 1 infected seedpiece10 ft-diameter area killed from 1 infected seedpiece• = 25% of the area of the field= 25% of the area of the field
W. R. Stevenson, UW-Madison
Tougher seed standardsTougher seed standardsCurrently allow 1% seed infection Currently allow 1% seed infection Some states force growers to plant only certified Some states force growers to plant only certified
seedseedRejection of seed lots when late blight on foliageRejection of seed lots when late blight on foliageWould a field be rejected for 1? 10? 100? 1000? Would a field be rejected for 1? 10? 100? 1000?
lesions per field??lesions per field??Can we predict tuber infection on basis of foliage Can we predict tuber infection on basis of foliage
infection??infection??
Tougher seed standardsTougher seed standardsCurrently allow 1% seed infection Currently allow 1% seed infection Some states force growers to plant only certified Some states force growers to plant only certified
seedseedRejection of seed lots when late blight on foliageRejection of seed lots when late blight on foliageWould a field be rejected for 1? 10? 100? 1000? Would a field be rejected for 1? 10? 100? 1000?
lesions per field??lesions per field??Can we predict tuber infection on basis of foliage Can we predict tuber infection on basis of foliage
infection??infection??
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Rules regarding cull pilesRules regarding cull piles
WI – mandatory cull pile destruction by May 20WI – mandatory cull pile destruction by May 20
• BuryBury
• Grind and spreadGrind and spread
• LandfillLandfill
• Feed to livestockFeed to livestock
Rules regarding cull pilesRules regarding cull piles
WI – mandatory cull pile destruction by May 20WI – mandatory cull pile destruction by May 20
• BuryBury
• Grind and spreadGrind and spread
• LandfillLandfill
• Feed to livestockFeed to livestock
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Volunteer potatoesVolunteer potatoes
Mild winters or heavy early fall snowsMild winters or heavy early fall snows
Early season planting of row crops – peas, beans, Early season planting of row crops – peas, beans,
corncorn
Lack of effective herbicidesLack of effective herbicides
Are volunteers a public nuisance?Are volunteers a public nuisance?
Volunteer potatoesVolunteer potatoes
Mild winters or heavy early fall snowsMild winters or heavy early fall snows
Early season planting of row crops – peas, beans, Early season planting of row crops – peas, beans,
corncorn
Lack of effective herbicidesLack of effective herbicides
Are volunteers a public nuisance?Are volunteers a public nuisance?
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Seed purchase and handlingSeed purchase and handling
Know the seed growerKnow the seed grower
• Visit the grower, walk the fields, view the Visit the grower, walk the fields, view the storagesstorages
Ask for field records – Ask for field records –
• IPM scoutsIPM scouts
• Certification inspectorsCertification inspectors
• Shipping point inspection Shipping point inspection
Seed purchase and handlingSeed purchase and handling
Know the seed growerKnow the seed grower
• Visit the grower, walk the fields, view the Visit the grower, walk the fields, view the storagesstorages
Ask for field records – Ask for field records –
• IPM scoutsIPM scouts
• Certification inspectorsCertification inspectors
• Shipping point inspection Shipping point inspection
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
If late blight If late blight riskrisk associated with seed - associated with seed - Consider treating seed with Tops/MZ/Curzate = Consider treating seed with Tops/MZ/Curzate =
EvolveEvolveConsider treating field with protectant fungicide at Consider treating field with protectant fungicide at
emergence emergence
If late blight pathogen If late blight pathogen confirmedconfirmed on seed - on seed - Consider the consequences of planting infected seedConsider the consequences of planting infected seed
• Increased management costsIncreased management costs
• Risk to crop in field and storageRisk to crop in field and storage
• Community source of late blightCommunity source of late blight
If late blight If late blight riskrisk associated with seed - associated with seed - Consider treating seed with Tops/MZ/Curzate = Consider treating seed with Tops/MZ/Curzate =
EvolveEvolveConsider treating field with protectant fungicide at Consider treating field with protectant fungicide at
emergence emergence
If late blight pathogen If late blight pathogen confirmedconfirmed on seed - on seed - Consider the consequences of planting infected seedConsider the consequences of planting infected seed
• Increased management costsIncreased management costs
• Risk to crop in field and storageRisk to crop in field and storage
• Community source of late blightCommunity source of late blight
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
At emergence (risk of late blight in seed, volunteers or cull At emergence (risk of late blight in seed, volunteers or cull pile)pile)
Consider treatment with protectant fungicideConsider treatment with protectant fungicide
At row close or at 18 severity valuesAt row close or at 18 severity values
If no late blight, but risk high (18 severity values)If no late blight, but risk high (18 severity values)
• Protectant spray with chlorothalonil, mancozeb, Protectant spray with chlorothalonil, mancozeb, metiram…metiram…
• Repeat at 5-7 day interval depending on crop Repeat at 5-7 day interval depending on crop growth and weathergrowth and weather
At emergence (risk of late blight in seed, volunteers or cull At emergence (risk of late blight in seed, volunteers or cull pile)pile)
Consider treatment with protectant fungicideConsider treatment with protectant fungicide
At row close or at 18 severity valuesAt row close or at 18 severity values
If no late blight, but risk high (18 severity values)If no late blight, but risk high (18 severity values)
• Protectant spray with chlorothalonil, mancozeb, Protectant spray with chlorothalonil, mancozeb, metiram…metiram…
• Repeat at 5-7 day interval depending on crop Repeat at 5-7 day interval depending on crop growth and weathergrowth and weather
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
If late blight present in area, but not in fieldIf late blight present in area, but not in field
• Treat with cymoxanil plus chlorothalonil, Treat with cymoxanil plus chlorothalonil,
mancozeb, metiram immediatelymancozeb, metiram immediately
• Continue at tight interval for three sprays then Continue at tight interval for three sprays then
protectant aloneprotectant alone
If late blight present in area, but not in fieldIf late blight present in area, but not in field
• Treat with cymoxanil plus chlorothalonil, Treat with cymoxanil plus chlorothalonil,
mancozeb, metiram immediatelymancozeb, metiram immediately
• Continue at tight interval for three sprays then Continue at tight interval for three sprays then
protectant aloneprotectant alone
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
If late blight present in field in pocketsIf late blight present in field in pockets
• Disk hot spots with perimeterDisk hot spots with perimeter
• Treat rest of field and adjacent fields with Treat rest of field and adjacent fields with
cymoxanil immediately, and again in 5 dayscymoxanil immediately, and again in 5 days
• Then continue with protectant programThen continue with protectant program
If late blight present in field in pocketsIf late blight present in field in pockets
• Disk hot spots with perimeterDisk hot spots with perimeter
• Treat rest of field and adjacent fields with Treat rest of field and adjacent fields with
cymoxanil immediately, and again in 5 dayscymoxanil immediately, and again in 5 days
• Then continue with protectant programThen continue with protectant program
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Late blight throughout fieldLate blight throughout field
• Destroy field immediately and treat adjacent Destroy field immediately and treat adjacent
fields with famoxate/cymoxanil immediately and fields with famoxate/cymoxanil immediately and
again in 5 daysagain in 5 days
• Continue with protectant programContinue with protectant program
Late blight throughout fieldLate blight throughout field
• Destroy field immediately and treat adjacent Destroy field immediately and treat adjacent
fields with famoxate/cymoxanil immediately and fields with famoxate/cymoxanil immediately and
again in 5 daysagain in 5 days
• Continue with protectant programContinue with protectant program
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Mid SeasonMid Season
Focus on protectant program that may include Focus on protectant program that may include
Curzate, Acrobat or TattooCurzate, Acrobat or Tattoo
Scout fields weekly or even more oftenScout fields weekly or even more often
Careful irrigation to avoid excessCareful irrigation to avoid excess
Mid SeasonMid Season
Focus on protectant program that may include Focus on protectant program that may include
Curzate, Acrobat or TattooCurzate, Acrobat or Tattoo
Scout fields weekly or even more oftenScout fields weekly or even more often
Careful irrigation to avoid excessCareful irrigation to avoid excess
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Late SeasonLate Season
Focus on protectant program that may include Focus on protectant program that may include
Acrobat, TattooAcrobat, Tattoo
Apply vine desiccant to protect size of seed potatoes Apply vine desiccant to protect size of seed potatoes
and to allow at least 3 weeks of dead vines before and to allow at least 3 weeks of dead vines before
harvestharvest
Careful irrigation to avoid excessCareful irrigation to avoid excess
Late SeasonLate Season
Focus on protectant program that may include Focus on protectant program that may include
Acrobat, TattooAcrobat, Tattoo
Apply vine desiccant to protect size of seed potatoes Apply vine desiccant to protect size of seed potatoes
and to allow at least 3 weeks of dead vines before and to allow at least 3 weeks of dead vines before
harvestharvest
Careful irrigation to avoid excessCareful irrigation to avoid excess
Breaking The CycleBreaking The Cycle
W. R. Stevenson, UW-Madison
Effective late blight strategy focuses on:Effective late blight strategy focuses on:
Keeping the fungal pathogen out of the planting areaKeeping the fungal pathogen out of the planting area
Intensive monitoring of every fieldIntensive monitoring of every field
Careful monitoring of weather conditionsCareful monitoring of weather conditions
Careful application of fungicideCareful application of fungicide
Partnership between each and every growerPartnership between each and every grower
Prompt response to local outbreaksPrompt response to local outbreaks
Effective late blight strategy focuses on:Effective late blight strategy focuses on:
Keeping the fungal pathogen out of the planting areaKeeping the fungal pathogen out of the planting area
Intensive monitoring of every fieldIntensive monitoring of every field
Careful monitoring of weather conditionsCareful monitoring of weather conditions
Careful application of fungicideCareful application of fungicide
Partnership between each and every growerPartnership between each and every grower
Prompt response to local outbreaksPrompt response to local outbreaks
Summary