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Keeping Potatoes Healthy fromPlanting to Harvest

Jeff Miller

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Fusarium sambucinum symptoms

Fusarium coeruleum symptoms

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Fusarium Dry Rot Management

1. Purchase seed with as little dry rot as possible.

2. Sterilize seed cutting equipment.

3. Sharpen seed cutting knives.

4. Avoid pre-cutting, if possible.

5. Treat with an effective seed treatment.

6. Minimize wounding at harvest.

7. Post-harvest treatment with Stadium

Risk of Precut vs. Cut/Plant – F. sambucinum

Cut/Plant

Precut/Store

0

20

40

60

80

100

Check MZ dust Tops Polyram

0 0

18 16

89

44

73

100

%Se

edw

ith

F.sa

mb

uci

nu

m

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a

c

bc

b

bc

a

0 20 40 60 80 100

UTC

Maxim MZ (0.5)

Moncoat MZ (0.75)

Maxim 4 FS (0.04)

Maxim 4 FS (0.08)

Quadris IF (8.7)

% of Seed Pieces Decayed

In-furrow applications are not effective.

Effect of Seed Treatments on Fusarium Seed Piece Decay

Which seed treatment do I use?

• Mancozeb (EBDC)

• Fludioxonil/Difenoconazole

– CruiserMaxx Potato Extreme

• Prothioconazole

– Emesto Silver

Also effectiveagainst silver scurf

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Influence of Environment and Seed on Silver Scurf

PN-MMZ

PN-UTCG3-MMZG3-UTC0

10203040506070

Inci

dence

Seed source was more important than location (soil).

Seed treatment effectively reduced disease incidence.

Rhizoctonia on June 21

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Rhizoctonia Stolon Canker

Severe Stem Rhizoctonia

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Untreated Check Priaxor, 6.75 fl oz Quadris, 9.2 fl oz Elatus, 7.7 oz

(Sercadis) (Aprovia + Quadris)

Rhizoctonia Stem Canker - 2018June 13, 49 DAP

ab

ede

c

a

d

b

0

5

10

15

20

25

30

35

40

45

50

UTC Elatus CMPE +Elatus

Quadris Velum Prime Moncut Vertisan

%S

eve

rity

Elatus = benzovindiflupyr + azoxystrobin

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Rhizoctonia Stem Canker - 2018July 17, 83 DAP

a

bcc

c

a

b b

0

5

10

15

20

25

30

35

40

45

50

UTC Elatus CMPE +Elatus

Quadris Velum Prime Moncut Vertisan

%S

eve

rity

Elatus = benzovindiflupyr + azoxystrobin

Tuber Quality - 2018

0% 20% 40% 60% 80% 100%

UTC

Elatus

CMPE + Elatus

Quadris

Velum Prime

Moncut

Vertisan

US#1 US#2 < 4 oz Culls

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Tuber Black Scurf - 2018

a

cd d

bcd abc

abab

0

10

20

30

40

50

60

70

UTC Elatus CMPE +Elatus

Quadris Velum Prime Moncut Vertisan

Se

veri

tyIn

de

x

Elatus = benzovindiflupyr + azoxystrobin

Seed Treatments for Rhizoc Canker

0

2

4

6

8

10

12

UTC CMP Extreme Emesto Silver

%R

oo

tSy

stem

Aff

ecte

d

18-Jun 20-Jul

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1. EBDC, fludioxonil/difenoconazole, andpenflufen/prothioconazole effective against dry rot.

2. Fludi/difen and pen/prothio effective against silver scurf andRhizoctonia.

3. In-furrow fungicide applications do not control Fusarium dryrot but can suppress silver scurf and Rhizoc

Seed Treatment/In-Furrow Summary

Pink Rot

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Pink Rot Management

1. Field selection/crop rotation

2. Adjust soil pH by lime application in low pH soils

3. Plant less susceptible varieties

4. Proper irrigation management

5. Use appropriate fungicides

6. Avoid “disease-favorable” conditions at harvest

7. Apply post-harvest fungicides

8. Grade out infected tubers going into storage

9. Reduce tuber pulp temperatures to 55 F or lower

Effect of Fungicide Programs on Pink Rot

May 4In-furrow

July 5Dime-size (DS)

July 19DS + 14 days

Aug 2DS + 28

Aug 16DS + 42

(Untreated check)

RidomilGold

Ridomil Gold Cu, 0.9 kg

MetaStar, 378 ml

Crop-phite, 4.7 L

Crop-phite, 3.5 L

0 2 4 6 8 10

a

bc

bcd

cd

d

ab

Mixed population (mefenoxam sensitive and resistant)

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How important is the time between application and irrigation?

a

b bb

ab

0

1

2

3

4

5

6

7

8

9

10

UTC 48 24 12 6

% Pink Rot

Time between Resist 57 (4.7 L/acre) application and irrigation (center pivot)

Effect of Orondis Gold IF on Pink Rot

a

b

bcd cdd

bc

0

1

2

3

4

5

6

7

Check Orondis Gold(13.8 fl oz/a)

Orondis Gold(10.8 fl oz/a)

Orondis Gold(13.8 fl oz/a) +Ridomil Gold

Bravo (2.5 pt/a)

Orondis Gold(10.8 fl oz/a) +Ridomil Gold

Bravo (2.5 pt/a)

Ridomil GoldBravo (2.5 pt/a)

%P

ink

Ro

tTu

ber

s

In-furrow applications

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Fungicides – Late BlightActive Ingredient Trade Names Relative Activity (1-3) Other Diseases

Cyazofamid Ranman, Torrent 3 None

Zoxamide/mancozeb Gavel 3 Early blight

Cymoxanil Curzate 2 None

Fluazinam Allegro 2 White mold

Phosphonates Confine Extra, Phostrol,Rampart

Foliar = 1Tubers = 3

Pink rot

Dimethomorph Acrobat, Forum, Zampro 2 None

Mandipropamid Revus, Orondis Ultra 3 None

Oxathiapiprolin Orondis Ultra, Orondis Gold 3 Pink rot (OG)

Fluopicolide Presidio Pink rot?

Ametoctradin/dimethomorph Zampro 3 None

Coppers Kocide, Parasol, Coppercide,Cueva, Copper Spray, Copper

1 None

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Fungicides – Pink RotActive Ingredient Trade Names Relative Activity (1-3) Other Diseases

Metalaxyl-M Ridomil Gold 480 SLRidomil Gold MZRidomil Gold Bravo

3 Late blightLate and early blightLate and early blight

Phosphonates Phostrol 2-3 Late blight

Fluopicolide Presidio 1-2 Late blight

Oxathiapiprolin Orondis Ultra, Orondis Gold 3 Pink rot

11 Fungicide classes available.- Many are highly effective

4 Fungicide classes available.- 1 has resistance- 1 works moderately well

How bad does this bother you?

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Avoid Disease Favorable Conditions at Harvest

0

10

20

30

40

50

60

70

16 21

Effect of Wounding and Pulp Temperature on Pink Rot

Wounded

Non-Wounded

0

10

20

30

40

50

60

70

80

90

100

13 16 18 21

%In

cid

ence

Early Storage Temperature (°F)

Tubers Stored from 13 to 21°C After Inoculatedwith Harvest Pulp Temperatures of 16 and 21°C

16 21

Harvest PulpTemperatures

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13 16 18 21(°C)

Post-Harvest Fungicides: Pink Rot and Late Blight

• Phosphorous acid:

– 0.42 L/tonne tubers

– Apply in 2 L water

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Post-Harvest Treatment: Pink Rot

0

20

40

60

80

100

0 1 2 3 4 5 6

%P

ink

RotT

ubers Untreated

HPPA

PA

Post-inoculation Interval (Hours)HPPA = Hydrogen peroxide/peroxyacetic acid (Oxidate)PA = phosphorous acid (Phostrol)

Post-Harvest Treatment: Late Blight

0

20

40

60

80

100

0 1 2 3 4 5 6

%P

ink

RotT

ubers

Untreated

HPPA

PA

Post-inoculation Interval (Hours)HPPA = Hydrogen peroxide/peroxyacetic acid (Oxidate)PA = phosphorous acid (Phostrol)

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Post-Harvest Treatment: Silver Scurf

• Evaluated 2 products(Phostrol/Resist 57)

• 3 rates (325, 416, 499 ml/tonne)

• 3 volumes (1.0, 2.1, 4.2 L/tonne)

• No difference in products used(Phostrol and Resist 57)

0

10

20

30

40

50

60

70

80

% incidence

Phos acidNone

Dry and 0.25 gal/T

Dry and 1.0 gal/T

Dry and 2.0 gal/T

Dry and 0.50 gal/T

Post-harvest spray application volumes

1 L/tonne

2.1 L/tonne4.2 L/tonne

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Questions?