2021-02 Powdery Scab and PMTV - Miller Research

2/23/2021

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Management of Powdery Scab andPotato Mop Top Virus

Jeff Miller, James Woodhall, and Nora Olsen

Photo from Ueli MerzPhoto from Ueli Merz

Photo from Ueli Merz

Photo from Ueli Merz

S pongosporasubterraneasubsp. subterranea(Protozoa)

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PMTV

• Foliar symptoms not associated with primary infection.

• Foliar = similar to calico.

• Symptoms favored by cool weather.

• Tuber = necrotic arcs (may require alternating storage temperatures todevelop).

– Can look like TRV, PVYntn, internal brown spot

• Symptoms increase with time in storage

• Can cause external symptoms

Photos courtesy of Jonathan Whitworth

Which one is PMTV? TRV?

PMTVTRV

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Photo courtesy of Jonathan Whitworth

PMTV Positive

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Powdery Scab Disease Cycle

• Environmental conditions which favor disease:

– Cool, wet soil

– 52-65°F

– Alternating wet/dry conditions

– Excessive soil moisture (especially 3-4 weeks after TI)

• Sandy soils and poor drainage more conducive for disease.

• Tuber infection typically occurs at tuber initiation.

• Very little inoculum required to cause disease.

Powdery Scab Management

• Longer crop rotation - > 5 years (12 year survival).

• Avoid planting in contaminated, poorly drained soils.

• Plant disease-free seed in disease-free areas.

• Avoid using manure if animals ingested infected tubers.

• Plant resistant cultivars.

• Carefully manage irrigation water.

• Use of fertility, pesticides?

Compendium of Potato Diseases, 2nd Ed.Falloon, AJPR (2008) 85:253-260

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Effect of Seed on Powdery Scab

0

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Diseased Visually disease free Mini-tubers

Trial 1 Trial 2

Tegg et al., 2016, AJPR 93:231-238

Effect of Seed/Soil Inoculum on Powdery Scab

Dr. Rob Davidson, Practical Management of Powdery Scab, Focus on Potato

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Use of Fertility/Fungicides

• Sulfur

• Manganese

• Zinc salts

• Mancozeb

• Metam fumigation

• Chloropicrin

• Fluazinam (Omega)

2002 Fungicide TrialRexburg, ID

05

1015202530354045

Ro

ot

gall

ind

ex

Shepody

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05

1015202530354045

Ro

ot

gall

ind

ex

Russet Burbank


05

1015202530354045

Tub

er

gall

ind

ex

Shepody

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2003 Fungicide TrialMinidoka, ID

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UTC Rid GoldMZ

Rid GoldMZ

Rid GoldMZ

Phostrol Phostrol Phostrol Omega Gavel Moncut

Tub

er

gall

ind

ex

Shepody

AirAir Chem Chem Irr Irr Irr IrrIrr


0

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UTC Evolve (12) Forum IF(6)

Forum Fol(6)

Headline IF(9)

HeadlineFol (9)

Rid GoldBravo +Phostrol

Bli-nix Fosphite

Tub

er

gall

ind

ex

Shepody

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Effect of Fluazinam (Omega) on Powdery ScabDr. Rob Davidson, Colorado State, cv. Cherry Red

aa

ab

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d

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UTC Maxim (0.08) Omega (1.5), 1nozzle

Omega (1.5), 2nozzles

Maxim(0.08) +Omega (1.5), 2

%In

fect

edTu

ber

s

2006 2007NSD in 2007


Effect of Fluazinam (Omega) on Tuber GradeDr. Rob Davidson, Colorado State, cv. Cherry Red

a

bc b

bcdcd

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UTC Maxim (0.08) Omega (1.5), 1nozzle

Omega (1.5), 2nozzles

Maxim(0.08) +Omega (1.5), 2

%U

nm

arke

tab

leTu

ber

s

2006 2007NSD in 2007


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Effect of Chemical Treatment on Scab and PMTV

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Tubers w/ Ps PMTV w/ PS PMTV w/o PS

%In

cid

ence

Russet Norkotah Line 8

Omega RIDEZ Control

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%In

cid

ence

Canela Russet

Omega RIDEZ Control

Zeng et al., 2020, Plant Disease 104:2807-2816

Two-nozzle design – Dr. Rob Davidson, CSU

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Theory behind broadcast application

Theory behind in-furrow application

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Effect of Fumigation on Powdery Scab

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Chloropicrin (178 lb/a) Chloropicrin (356 lb/a) PIC 33% + DCP 66% (267 lb/a) PIC 33% + DCP 66% (445 lb/a)

%R

edu

ctio

nvs

Co

ntr

ol

Plastic Cover No Cover

Tsror (Lahkim) et al., 2019, Crop Protection 124:104836

Metam Sodium on Powdery Scab

• Water-applied Metamor (51% MS):

– 68% reduction at 46 gal/acre (=56 gal Vapam)

– 80% reduction at 66 gal/acre (=80 gal Vapam)

• Data for ground application

– Significant PS reported under metam-fumigated conditions

• More research needed in southern Idaho conditions

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Cultivar Susceptibility to Powdery Scab in Idaho

0 10 20 30 40

Ivory Crisp

Shepody

Chipeta

FL 1533

Atlantic

Defender

Umatilla

Ida Rose

Superior

Liberator

Alturas

Russet Burbank

Ranger Russet

Yukon Gold

Bannock Russet

Harley Blackwell

Russet Norkotah

Gem Russet

Summit Russet

Root gall index

0 5 10 15 20 25

Shepody

Chipeta

Ida Rose

Liberator

Ivory Crisp

Yukon Gold

FL1533

Atlantic

Superior

Defender

Harley Blackwell

Alturas

Ranger Russet

Summit Russet

Umatilla

Russet Norkotah

Bannock Russet

Gem Russet

Russet Burbank

Tuber scab index

Haynes et al., AJPR 82:73 and 83:113

Bittara and Robinson, Powdery Scab of Potatoes, PP1891, June 2018.

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Cultivar susceptibility to PMTV symptoms (NDSU)

Sensitive (>15%) Moderately Sensitive(10-15%)

Moderately Insensitive(5 -10%)

Insensitive (<5%)

Dark Red Norland Red Norland Alpine Russet Red Gold

Modoc Chieftain Ciklamen Red Tumb

Viking Snowden Dakota Ruby Colorado Rose

Dakota Crisp Red La Soda Bintje

Yukon Gold LaMoka

Alturas

Most russets

Powdery Scab - Variety% Incidence

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Burbank Ranger Norkotah 296 Alturas Umatilla Teton Clearwater Dakota

%P

lan

tsA

ffec

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Powdery Scab - VarietySeverity (0-5)

bc

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PMTV - Variety% Incidence of visible symptoms

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%Tu

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Interaction between variety and treatment was not significant.

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Effect of Chemical Treatment on Scab and PMTV

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%In

cid

ence

Russet Norkotah Line 8

Omega RIDEZ Control

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%In

cid

ence

Canela Russet

Omega RIDEZ Control

Zeng et al., 2020, Plant Disease 104:2807-2816

Soil Moisture – Powdery Scab and PMTV

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Wet Dry, wet Wet, dry Dry

%Tu

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Powdery scab

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Wet Dry, wet Wet, dry Dry

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PMTV Tuber Necrosis

Domfeh and Gudmestad, 2016

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Summary

• More research needed on the effects of fertility (e.g. zinc, manganese)

• Fungicide performance is inconsistent at best.

– Two nozzle application of Omega (1.5 pt) may offer some control.

– Research needed on broadcast vs in-furrow.

• Fumigation was effective if covered (chloropicrin) or water-run (metam).

• Russet cultivars generally more resistant varieties to tuber lesions.

• Link between PS symptoms and PMTV symptoms not solid.

• Keeping soil dry = lower PS on tubers and PMTV symptoms

Documents

2021-02 Powdery Scab and PMTV - Miller Research