A dynamic model fordowny mildew primary

infection on grape

Bugiani R. Brunelli A. Collina M.

Rossi V. Giosué S. Caffi T. Girometta B.

Spanna F.

Many forecasting models forP.viticola primary infection,

were developed

None of them proved to be precise and robust

Current warning systems are mainly based on “Three 10 Rule”

In spite of the fact it is often unreliable

A new approach:- Pathosystem analysis- data and information collection- mathematic relationships build-up- dynamic simulation

ValidationEmilia-Romagna 1995 – 2002, several localitiesPiemonte 1999 –2002, several localitiesOltrepò Pavese 1998 – 2002

In 2003Emilia-RomagnaPiemonte

Oosporelatency Temperature

Water presence

Germination

Infection

zoosporangiasurvival

Zoosporesurvival

TemperatureRelative humidity

Zoosporeliberation

TemperatureLeaf wetness

Spread

Rainfall

Symptomsoccurrence

Incubation

TemperatureRelative Humidity

Water presence

THE

MODEL

THE

MODEL

Start

Oosporemature

Spore germination

Presenceof rain

No

Y

Presence of sporangia

Presence ofzoospore

End

Wetness

Presenceof water

Presenceof Rain

SurvivedSporangia

Presence ofwetness Infection

Zoospore death

Zoospores on the leaves

No

Y

No

No

No

No

NoY

Y

Y

Y

Y

1.Oospore latency

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.51/

1

15/1

29/1

12/2

26/2

12/3

26/3 9/4

23/4

IMO

1999

2000

2001

2002

IMO = f (T, VPD)

Index of Oospore Maturation(IMO)

THE

MODEL

1.Oospore latency

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.51/

1

15/1

29/1

12/2

26/2

12/3

26/3 9/4

23/4 7/5

21/5

IMOmin

IMOmax

Period of oospore

maturation

IMO

THE

MODEL

2. Oospore germination

Coorts of matureoospores

Frequency of mature oospores

Start of germination

f (R)

IMOmaxIMOmin

THE

MODEL Period of

oosporematuration

2. Oospore germination

10/4

15/4

20/4

25/4

30/4 5/5

10/5

15/5

20/5

25/5

30/5

1

0.8

0.6

0.4

0.2

0

IGO

IGO = f (T, VPD)Index of Oosporegermination (IGO)

THE

MODEL

3.Sporangia survival

10/4

15/4

20/4

25/4

30/4 5/5

10/5

15/5

20/5

25/5

30/5

SURmax= f (T, RH)

THE

MODEL

4.Sporangia germination5.Zoospore survival

f (T, LW)10

/4

15/4

20/4

25/4

30/4 5/5

10/5

15/5

20/5

25/5

30/5

f (LW)

THE

MODEL

6.Zoospores dispertion

f (R)10

/4

15/4

20/4

25/4

30/4 5/5

10/5

15/5

20/5

25/5

30/5

THE

MODEL

7.Infection

f (T, LW)10

/4

15/4

20/4

25/4

30/4 5/5

10/5

15/5

20/5

25/5

30/5

THE

MODEL

8.Incubation and symptom occurrence

f (T, RH)10

/4

15/4

20/4

25/4

30/4 5/5

10/5

15/5

20/5

25/5

30/5

THE

MODEL

Date of oospore observationGermination observedGermination expected

Asti 2000

1

1

2

2

3

3

4

4

5

5

6

6

30/3 4/4

9/4

14/4

19/4

24/4

29/4 4/5

9/5

14/5

19/5

24/5

29/5

y = 1.07x - 3.3R2 = 0.94

0

10

20

30

40

50

60

0 10 20 30 40 50 60Observed (days from 30/3)

Stim

ati

Asti 1999-2003

THE

VALI

DATI

ONS

–Oos

pore

germ

inat

ion

Velocity of oosporegermination

Estimated values of the modelvs

Observed values for oosporesoverwintered in vineyard(floating disk method)

Asti 1999-2003

Date primaty symptoms occurrenceTH

E VA

LIDATI

ONS

–Sy

mpt

omoc

curr

ence

Model’s estimated date vs Observed date in vineyard1/

4

8/4

15/4

22/4

29/4 6/5

13/5

20/5

27/5 3/6

10/6

17/6

24/6 1/7

8/7

15/7

22/7

29/7

0

10

20

30

40

50

60

70R (mm)

Oosporegermination

Zoosporerelease

Spread of zoospores

Infection

End of incubation

Occurrence

Symptomsoccurrence

05

10152025303540

%

28-1

/4

2-6/

4

7-11

/4

12-1

6/4

17-2

1/4

22-2

6/4

27-1

/5

2-6/

5

12-1

6/5

17-2

1/5

22-2

6/5

27-3

1/5

7-11

/5

1-5/

6

6-10

/6

11-1

5/6

16-2

0/6

21-2

5/6

26-3

0/6

1-5/

7

35

05

1015202530 % Infection

28-1

/4

2-6/

4

7-11

/4

12-1

6/4

17-2

1/4

22-2

6/4

27-1

/5

2-6/

5

12-1

6/5

17-2

1/5

22-2

6/5

27-3

1/5

7-11

/5

1-5/

6

6-10

/6

11-1

5/6

16-2

0/6

21-2

5/6

26-3

0/6

1-5/

7

28-1

/4

2-6/

4

7-11

/4

12-1

6/4

17-2

1/4

22-2

6/4

27-1

/5

2-6/

5

12-1

6/5

17-2

1/5

22-2

6/5

27-3

1/5

7-11

/5

1-5/

6

6-10

/6

11-1

5/6

16-2

0/6

21-2

5/6

26-3

0/6

1-5/

705

10152025303540

% 10 cm shoots

38 cases(locality x year)

THE

VALI

DATI

ONS

–Sy

mpt

omoc

curr

ence

THE

VALI

DTZ

IONS

–Sy

mpt

oms

occu

rren

ce308 simulations

no yes

232 075.3% 0%

17 59

5.5% 19.2%yes

no

Infe

ctio

nex

pect

edInfection observed

291 correct17 uncorrect

False alarms

Correct predictionsTH

E VA

LIDATI

ONS

–Sy

mpt

om o

ccur

renc

e

Oltrepò PV 2001

1/4

8/4

15/4

22/4

29/4 6/5

13/5 1/4

8/4

15/4

22/4

29/4 6/5

13/5

20/5

27/5

Carpineta (MO) 1996 Panocchia (PR) 1997

1/4

8/4

15/4

22/4

29/4 6/5

13/5

20/5

27/5 3/6

10/6

17/6

0

10

20

30

40

50

60

70

3/6

20/5

Correct predictionsTH

E VA

LIDATI

ONS

–Sy

mpt

om o

ccur

renc

eAlba (CN) 2002

0

20

40

60

80

100

0

20

40

60

80

100% of affected leaves

20/5

23/5

26/5

29/5 1/6

4/6

7/6

10/6

13/6

16/6

19/6

20/5

23/5

26/5

29/5 1/6

4/6

7/6

10/6

13/6

16/6

19/6

20/5

23/5

26/5

29/5 1/6

4/6

7/6

10/6

13/6

16/6

19/6

Ger

min

atio

nO

ospo

res

2/53/56/5

18/5

20/521/525/525/5

Infe

ctio

n2-3/54/5

8-9/5

18-19/5

23-25/523-26/525-29/527-29/5

End

of

incu

batio

n

13-16/514-16/515-18/5

24-27/5

29/5-1/629/5-1/631/5-3/6

1-4/6

12/415/419/4

7/5

10/512/516/518/5

Star

t of

Ger

min

atio

n

sporulations

THE

VALI

DATI

ONS

–Sy

mpt

om o

ccur

renc

eFalse alarms

28-1

/4

2-6/

4

7-11

/4

12-1

6/4

17-2

1/4

22-2

6/4

27-1

/5

2-6/

5

12-1

6/5

17-2

1/5

22-2

6/5

27-3

1/5

7-11

/5

1-5/

6

6-10

/6

11-1

5/6

16-2

0/6

21-2

5/6

26-3

0/6

1-5/

7

28-1

/4

2-6/

4

7-11

/4

12-1

6/4

17-2

1/4

22-2

6/4

27-1

/5

2-6/

5

12-1

6/5

17-2

1/5

22-2

6/5

27-3

1/5

7-11

/5

1-5/

6

6-10

/6

11-1

5/6

16-2

0/6

21-2

5/6

26-3

0/6

1-5/

705

10152025303540

% 10 cm shoots

01234567

N.

THE

VALI

DATI

ONS

–Sy

mpt

om o

ccur

renc

eFalse alarms

Lavezzola (RA) 1998

1/4

8/4

15/4

22/4

29/4 6/5

13/5

20/5

27/5 3/6

10/6

0

10

20

30

40

50

60

70S.Agata sul Santerno (RA) 1997

17/61/4

8/4

15/4

22/4

29/4 6/5

13/5

20/5

27/5 3/6

10/6

Castel Boglione

Asti

1/4

8/4

15/4

22/4

29/4 6/5

13/5

20/5

27/5 3/6

10/6

17/6

24/6 1/7

8/7

15/7

22/7

29/7

0

10

20

30

40

50

60

70Serralunga

THE

VALI

DATI

ONS

–Ye

ar20

03

0

10

20

30

40

50

60

70

Piacenza

Castelfranco Emilia1/

48/

415

/422

/429

/4 6/5

13/5

20/5

27/5 3/6

10/6

17/6

24/6 1/7

8/7

15/7

22/7

29/7

Altedo

THE

VALI

DATI

ONS

–Ye

ar20

03

The forecasting model proved to be: detailedIt followed, step by step, the whole infection processaccurateIt corretly estimated 94% of the cases It never provided wrong negative prognosisrobustIt estimate either early and late infectionsIt adapt itself with several epidemiological conditions

The model gave some false alarms

Conc

lusion

s and therefore it can be furtherly improved