Silver scurf, black scurf

and dry rot

Ragnhild Nærstad

Norwegian Institute for Agricultural and

Environmental Research

Bioforsk

Plant Health and Plant Protection Division

.

14 000 ha -> 350 000 tons = 25 t/ha (10 – 70 t/ha)

3000 growers, 1 – 80 ha of potatoes per grower

Silver scurf Helminthosporium solani

Silver scurf

• Potato is the only known host plant

• Survives as a saprophyte in soil, and multiplies

on senescent plants of many species

• Tubes can become infected in the growing

season, at harvest or during storage

• Needs humid conditions to infect, the infection

speed increases with temperature

• Under optimal conditions the fungus needs

9 hours to penetrate into the cells

Silver scurf

• Infected cells die, loose their pigments and

become filled with air –> silvery lesions

• Increased the water loss in infected tissue ->

shrinking

• Inoculum sources: Seed tubers (and soil)

• PCR results from 2008 - 2009: a lot of

inoculum in seed tubers and low levels in

soil

Control measures – Silver scurf

• Crop rotation + avoid cereals as the last crop before

potatoes

• Shorter growing seasons (presprout seed tubers)+

shorten the period between haulm killing and harvest

• Suppressive soils

• Low plant density

• Dry curing

• Cold storage and no condense

• Seed treatment: Fungazil (imazalil), Maxim

(fludioxonil), Emesto (penflufen), Emesto silver

(penflufen + protioconazol), Serenade (Basillus subtilis)

• In furrow fungicide application: Amistar (azoxystrobin)

Black scurf

Rhizoctonia solani

Sclerotia and

hypha

Black scurf Rhizoctonia solani

(Thanatephorus cucumeris)

• Sunken dark brown lesions on

sprouts, stems, stolons and roots

• Infections in stolons early in the

season -> tuber abortion, new

tubers is developed higher up ->

more small tubers and more green

tubers

Control measures – Black scurf

• Crop rotation, several years without potatoes

• Suppressive soils

• Shorter growing seasons + shorten the period between

haulm killing and harvest -> less sclerotia on tubers

• Dry curing

• Cold storage and no condense

• Seed treatment: Rizolex (tolclofosmethyl), Monceren

(pencycuron), Maxim (fludioxonil), Emesto

(penflufen), Emesto silver (penflufen + protioconazol)

Silver scurf

Silver scurf

Black dot

Plug test - incubation test

- distinguish between different types of scurfs

- visualize latent infection

Occurrence of skin blemish diseases in Norway

after 4 - 6 month of storage, 247 potato lots: Nærstad R, Dees MW, Le VH, Holgado R, Hermansen A

• Silver scurf (Helminthosporium solani) 11-13% (100%)

• Black dot (Colletotrichum coccodes) (80%)

• Common scab (Streptomyces spp.) 6-7% (50-70%)

• Powdery scab (Spongospora subterranean) 0.7-2% (70%)

• Skin spot (Polyscytalum pustulans) 0.2-1.7% (80%)

• Black scurf (Rhizoctonia solani) 0.8% (80%)

Root lesion nematodes

Paratylenchchus spp. in

60% of scabby lesions

Decision making in potato skin blemish

diseases control using real-time diagnostic

methods; Norwegian results from 2009 and

2010

R. Nærstad, A. Hermansen, V.H. Le,

G. Lund, M. Skogen, M.B. Brurberg

Sampling

• 40 locations each year in 2009 and 2010 + questionaries

• From each location:

– Samples of soil and seed tubers at planting

– Samples of soil in August

– Samples of progeny tubers at harvest

• Assessed for the presence of pathogens by real-time PCR

• Tubers were also assed for the presence of pathogens by plug tests

• Pathogens:

• Black dot (Colletotrichum coccodes)

• Skin spot (Polyscytalum pustulans)

• Common scab (Streptomyces spp.)

• Silver scurf (Helminthosporium solani)

• Powdery scab (Spongospora subterranean)

• Black scurf (Rhizoctonia solani)

Real-time PCR protocols

• SCRI protocols:

• Common scab (Cullen and Lees, 2007)

• Powdery scab (van de Graaf et al., 2003)

• Silver scurf (Cullen et al., 2001)

• Black scurf (Lees et al., 2002)

• Black dot (Cullen et al. 2002)

• Fungal pathogens based on ITS regions

• Streptomyces based on nec gene

18S gen 5.8S gen 26S gen

ITS Ribosomale RNA gener:

DNA-analysis

• Soil samples (SCRI protocol)

• Tuber samples

– Peel homogenized in Homex (SCRI protocol)

– Extraction robot (Molgene)

Example of amplification plot

Silver scurf Helminthosporium solani

543210

90

80

70

60

50

40

30

20

10

0

PCR-Silver scurf-progeny tubers

%S

-Silv

er

scu

rf-p

rog

en

y t

ub

ers

2009

2010

year

Scatterplot of %S-Silver scurf-progeny vs PCR-Silver scurf-progeny

• Good correlation between plug-test and PCR results

• High level of inoculum in seed tubers

• Low level of inoculum in soil

• Low correlation between inoculum in seed tubers and progeny tubers

543210

5,6

5,2

4,8

4,4

4,0

PCR-Silver scurf-progeny tubers

PC

R-S

ilve

r scu

rf-s

ee

d t

ub

ers

2009

2010

year

Scatterplot of PCR-Silver scurf-seed tu vs PCR-Silver scurf-progeny

5,65,24,84,44,0

100

80

60

40

20

0

PCR-Silver scurf-seed tubers

%S

-Silv

er

scu

rf-s

ee

d t

ub

ers

Scatterplot of %S-Silver scurf-seed tub vs PCR-Silver scurf-seed tu

Black scurf Rhizoctonia solani

6543210

2,5

2,0

1,5

1,0

0,5

0,0

PCR-black scurf- seed tubers

Scle

roti

a-

Se

ed

tu

be

rs

Scatterplot of Sclerotia- Seed tubers vs PCR-black scurf- seed tubers

• Good correlation between: sclerotia plug-test plug-test PCR results

• Low level of inoculum in soil in spring, a slight increase in the autumn, but did not correlate with the black scurf in the progeny

• Low correlation between inoculum in seed and progeny tubers

6543210

50

40

30

20

10

0

PCR-black scurf- seed tubers

%R

-Bla

ck s

cu

rf-s

ee

d t

ub

ers

Scatterplot of %R-Black scurf-seed tube vs PCR-black scurf- seed tu

9080706050403020100

5

4

3

2

1

0

%R-black scurf-progeny tubers

Scle

roti

a-p

rog

en

y t

ub

ers

2009

2010

Year

Scatterplot of Sclerotia-progeny tubers vs %R-black scurf-progeny t

Conclusion from quantitative PCR

diagnostics of soil and tubers

• Skin spot, powdery scab and black dot:

disease increased with inoculums on the seed

tubers.

• For black dot and powdery scab it also

increased with soil inoculums

• Common scab, silver surf and black scurf:

other factors than inoculums level were more

important for disease incidence in the progeny

tubers

Harvest, curing and storage strategies

3 trials

• 0, 11 and 22 days from haulm killing to

harvest

• 4 harvest dates

• Curing: 70% RH and 90% RH

• Storage: Directly to 4oC and slowly to 4oC

Seed treatment at planting (6 trials/year)

0

10

20

30

40

50

60

% progeny tubers with sclerotia (2005 and 2006)

% plugs with black scurf hyfae (2007)

% plugs with silver scurf (2007)

Control

Rizolex

Maxim

• Both Maxim (fludioxonil) and Rizolex

(tolclofosmethyl) reduces black scurf in the progeny

tubers (sclerotia og hypha)

• Maxim reduces silver scurf in the progeny

0

10

20

30

40

50

60

% plugs with silver scurf % plugs with black scurf hyfae

% plugs with skin spot

Effect of humidity during curing and Amistar in furrow

Control Humid curing

Control Dry curing

Amistar Humid curing

Amistar Dry curing

• All treatments reduced the

amount of R. solani sclerotia

and hypha on the progeny

tubers

• Amistar and Emesto also

reduced the frequency of

silver scurf latent infections

(plug test)

• In 2008 and 2010 there were

attack of black dot at one

location and in these trials

there were less black dot in

the Amistar treatment.

0

10

20

30

40

50

60

70

80

90

100

2008 2009 2010

% reduction of black scurf hyfae

Rizolex

Emesto

Amistar

Emesto dust

Emesto silver

Prestige

-100

-80

-60

-40

-20

0

20

40

60

80

100

2008 2009 2010

% reduction of silver scurf

Rizolex

Emesto

Amistar

Emesto dust

Emesto silver

Prestige

-40

-20

0

20

40

60

80

100

2008 2010

% reduction of black dot

Rizolex

Emesto

Amistar

Emesto dust

Emesto silver

Prestige

Fusarium dry rot

• Important disease of potato affecting tubers in

storage

• Caused by several fungal species in the genus

Fusarium

• Fusarium dry rot of seed tubers can reduce crop

establishment by killing developing potato sprouts

• Crop losses can be up to 25%

Symptoms

• Originate in wounds created by mechanical damages or

desprouting during handling

• Surface lesions appears as dark depressions and wrinkled

areas of skin

• Concentric rings can be observed in case of heavy infection

• Fusarium dry rot can be recognized based on white, pink or

orange colored mycelium proliferation on the tuber surface

Photos: J. Gomez

Fusarium dry rot in Norway

P.H. Jensen, M.B. Brurberg & A. Hermansen • Main goal: Find out which

Fusarium spp. currently causes

dry rot problems in Norway

• How: Potato samples collected

from different regions in Norway

over 3 seasons (2010-2013)

– artificial wounding +

incubation

– isolation

Photo: P. H. Jensen

Results from the growing season 2010 -2011

5 % of the tubers developed rots

Fusarium

Boeremia (Phoma)

Penicillium

Mucor

Cylindrocarbon

49 % of rots were caused by Fusarium

–F. coeruleum (64%)

–F. avenaceum (31%)

–F. culmorum (4%)

–F. cerealis (1%)

–F. sambucinum (1%)

Photo: P. H. Jensen

Fusarium sambucinum Fusarium culmorum

Fusarium coeruleum Fusarium cerealis

Goal

• Develop multiplex real time PCR for

Norwegian dry rots caused by Fusarium

species and gangrene (Boremia foveata)

Monceren FS 250(Pencycuron) Inhibition of cell division, phenylureas,

FRAC Code B4

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Monceren FS250 (Pencycuron in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Monceren FS250 (Pencycuron in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Monceren FS250 (Pencycuron in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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Monceren FS250 (Pencycuron in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Rizolex 50FW (Tolclofosmethyl) Lipid peroxidation, Aromatic Hydrocarbons,

FRAC Code F3

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Rizolex 50 FW(Tolclophosmethyl in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Rizolex 50 FW(Tolclophosmethyl in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Rizolex 50 FW(Tolclophosmethyl in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Rizolex 50 FW(Tolclophosmethyl in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Maxim 100 FS(fludioxonil) Inhibition of osmotic signal transduction, phenylpyrroles,

FRAC Code E2

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Maxim 100 FS (fludioxonil in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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Maxim 100 FS (Fludioxonil in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Maxim 100 FS (Fludioxonil in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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Maxim 100 FS (Fludioxonil in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Emesto(Penflufen) Inhibition of respiration complex II, Succinate DeHydrogenase Inhibitors,

FRAC Code C2

0

20

40

60

80

100

120

140

160

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

BYF14182 (Penflufen in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

20

40

60

80

100

120

140

160

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

BYF14182 (Penflufen in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

20

40

60

80

100

120

140

160

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

BYF14182 (Penflufen in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

20

40

60

80

100

120

140

160

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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BYF14182 (Penflufen in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Fungazil(Imazalil) Inhibition of sterol biosynthesis in membranes, DeMethylation Inhibitors,

FRAC Code G1

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Fungazil 100SL (Imazalil in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Fungazil 100SL (Imazalil in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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Fungazil 100SL (Imazalil in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

20

40

60

80

100

120

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

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Fungazil (Imazalil in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Proline EC250 (Protiokonazol) Inhibition of sterol biosynthesis in membranes, DeMethylation Inhibitors,

FRAC Code G1

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Proline EC250 (Protiokonazol in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Proline EC250 (Protiokonazol in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Proline EC250 (Protiokonazol in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

20

40

60

80

100

120

140

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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l

Proline EC250 (Protiokonazol in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Amistar (azoxystrobin) + Salicylhydroxamic acid Inhibition of respiration complex III, Quinone outside inhibitors

FRAC Code C3,

0

25

50

75

100

125

150

175

200

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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Amistar (Azoxystrobin in ppm )

Colletotrichum coccodes

No08-Cc-016

No08-Cc-037

No08-Cc-057

No08-Cc-10

No08-Cc-13

No08-Cc-19

No08-Cc-42

No08-Cc-43

No08-Cc-47

No08-Cc-50

0

25

50

75

100

125

150

175

200

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

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Amistar (Azoxystrobin in ppm )

Helminthosporium solani

No08-Hs-059

No08-Hs-060

No08-Hs-062

No08-Hs-067

No08-Hs-020

No08-Hs-021

No08-Hs-027

No08-Hs-029

No08-Hs-035

No08-Hs-041

0

25

50

75

100

125

150

175

200

0,01 0,10 1,00 10,00 100,00

Gro

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in %

of

con

tro

l

Amistar (Azoxystrobin in ppm )

Polyscytalum pustulans

No08-Pp-034

No08-Pp-043

No08-Pp-048

No08-Pp-053

No08-Pp-001

No08-Pp-005

No08-Pp-009

No08-Pp-011

No08-Pp-012

No08-Pp-015

0

25

50

75

100

125

150

175

200

0,01 0,10 1,00 10,00 100,00

Gro

wth

in %

of

con

tro

l

Amistar (Azoxystrobin in ppm )

Rhizoctonia solani

No08-Rs-020

No08-Rs-025

No08-Rs-027

No08-Rs-130

No08-Rs-004

No08-Rs-011

No08-Rs-013

No08-Rs-014

No08-Rs-016

No08-Rs-019

Application of seed treatment in

autumn or spring ?

The control had silver scurf on 50% of the plugs

and black scurf on 12 % of the plugs =>no

significant differenses between treatments for

black scurf.

0

10

20

30

40

50

60

70

80

90

100

Autumn Spring Autumn + spring

% control of silvers curf in progeny tubers

Imazalil sulfat

Fludioxonil

Copperoxide

Penflufen