A spatial model for predicting Swiss needle cast distribution and severity

Jeff Stone and Len CoopDepertment of Botany and Plant Pathology

Oregon State University

Acres of Douglas-fir forest with Swiss Needle Cast Symptoms Detected by Aerial Surveys, Coast Range, Oregon 1996-2006

131,088144,102

172,127

293,649 282,202

212,465

387,040

267,852

176,594

207,090

324,584

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Survey data, two types: area and symptom severity.

Both vary due to annual weather effects

Spatial distribution of disease occurrence and severity are neither random nor uniform

Both temporal and spatial occurrence of disease are affected by short (weather) and long (climate) term meteorological patterns

Average disease severity is related to total area affected

SNC Index = survey area x survey average severity

Annual area and severity of SNC is correlated with seasonally-grouped climate variables that have also been correlated with abundance of P.

gaeumannii

Predicting Swiss Needle Cast Severity

The best predictors of disease severity in permanent study sites are mean daily winter temperature and spring leaf wetness, because of their effects on infection and pathogen growth

Observed Infection Index

0.0 0.1 0.2 0.3 0.4

Pre

dic

ted

In

fectio

n In

de

x

0.0

0.1

0.2

0.3

0.4

one-yr needlestwo-yr needles

R2=0.794

Predicted vs. observed values for amount of infecton in Douglas-fir stands in the Coast Range, based on winter (Dec-Feb) average daily temperature, spring leaf wetness.

Year

0 5 10 15 20

Pseu

doth

ecia

den

sity

(%

)

0

5

10

15

20

Simulation of Phaeocryptopus gaeumannii pseudothecia density over time for one-year-old and two-year-old needles. Mean-daily winter temperature was held constant at 5.13 ºC and the initial infection index was set to 1.0 %.

Mean-daily winter temperature ( oC)

2 4 6 8 10

Pseu

doth

ecia

den

sity

(%

)

-10

0

10

20

30

40

50

Simulated final Phaeocryptopus gaeumannii infection index for one-year-old and two-year-old needles over a range of constant winter temperatures. Vertical lines represent the high (8.90 ºC) and low (3.77 ºC) mean-daily winter temperatures observed from coastal study sites.

2-yr-old

1-yr-old

2-yr-old

1-yr-old

Disease severity prediction for NW Oregon based on DAYMET climate model, 17-year average temperatures

New Zealand Plantations sampled in 2006

Distribution of SNC in New Zealand also is strongly correlated with climate factors affecting abundance of P. gaeumannii

45

Composite Needle Retention

0

5

10

15

20

25

30

35

Karioi

Hanmer

(all)

Gowan

Hills

SS

Golden

Dow

ns P

Gowan

Hills

P

Golden

Dow

ns S

S

Beaum

ont (a

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Skain

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a

Kainga

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(all)

Waipor

i (all

)

Tauhar

a (all)

Putor

ino

Waira

ngi

Puketitr

i

TeWaka

Nee

de

Ret

enti

on

Sco

reNeedle Retention by Age Class

0

1

2

3

4

5

6

7

8

9

10

Karioi

Hanmer

(all)

Gowan

Hills

SS

Golden

Dow

ns P

Gowan

Hills

P

Golden

Dow

ns S

S

Beaum

ont (

all)

Skaing

aroa

Kainga

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(all)

Waip

ori (

all)

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Putor

ino

Wair

angi

Puket

itri

TeWak

a

Ne

ed

le R

ete

nti

on

Sc

ore

2004 2003 2002 2001

Average needle retention for New

Zealand sites

2004 Infection Index

0.000

2.000

4.000

6.000

8.000

10.000

12.000

14.000

16.000

HS-900

GH-S

S-900

MNK-9

00

GH-P

-900

GD-P

-900

GD-S

S-900

BEAUMT-9

00SK

WAI-9

00TAK

PUKTW

A

KGA-9

00

TAU-900

WRI

PTO

2003 Infection Index

0.000

5.000

10.000

15.000

20.000

25.000

30.000

35.000

40.000

GH-S

S-900

MNK-9

00

HS-900

GH-P

-900

BEAUMT-9

00

WAI-9

00TAK

GD-P

-900

GD-S

S-900

PUKW

RIPTO

TAU-900 SK

TWA

KGA-9

00

Abundance of pseudothecia on one-

and two-year-old foliage

AC 2004 Vs Winter Min Temp

y = 0.3195x - 0.8817R2 = 0.8494

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000 16.000

Relationship between mean daily minimum winter temperature and P. gaeumannii abundance in New Zealand

Climate/weather factors are the major determinants of P. gaeumannii abundance and SNC severity, regardless

of location

But in western Coast Range, spatial distribution of disease over time is aggregated, does not strictly follow elevational gradients etc.

Distribution and severity of Swiss needle cast 1996-2006, Tillamook area

Cumulative disease distribution appears to be strongly influenced by aspects of topography, wind direction and other meteorological variables in addition to temperature—need to allow for maritime influence in models.

Summer maritime influences cause wind convergence zones (outlined in red)

Convergence zones occur in the near-surface wind field below the marine inversion during onshore flow in marine stratus regimes. These convergence zones typically have the highest occurrence of drizzle and cloud.

Areas of highest disease severity appear to coincide with zones having an optimal mixture of marine drizzle and leafwetness with the warmer temperatures.

Effects of convergence/divergence

Elements are in place to develop a useful, predictive spatial model for Swiss needle cast:

Infection biology, epidemiology, mechanism of pathogenicity of the pathogen are well understood

Environmental variables affecting distribution and abundance of the pathogen are well understood, mechanistic, and strongly correlated with disease distribution.

Sufficiently detailed, high resolution GIS-based climate datasets are available, readily adaptable for SNC modeling.

Considerable data are available on disease distribution and P. gaeumannii abundance over the past ten years, both site specific and aerial survey.

The OSU Integrated Plant Protection Center is a nationally recognized center for plant disease modeling and forecasting.

The PIs combined expertise in GIS-modeling, climate modeling, disease forecasting, and epidemiology of SNC.

Using CALMET and MtnRTCon together to specify marine stratus precipitation in summer for Swiss

Needle Cast Alan Fox

Fox Weather, LLC9/21/06

Sample Products from CALMET

• Map of Temperature• Map of Wind Speed• Map of Mixing Height (base of marine

inversion)

Sample Products from CALMET

Wind Direction/Speed (mph) Mixing Height (meters)

24hr forecast valid 08/29/2006 10am PSTFIGURE 1.

Sample Products from CALMET

24hr Forecast Valid 10am 8/24/2006

Summary of CALMET Forecasts in Figures 1 and 2

• Mixing height = depth of the marine layer (existing below the inversion). The top of the mixing layer would normally correspond to the cloud top in marine stratus patterns.

• Wind direction/speed: shows areas of convergence and divergence around terrain barriers, which, in the marine layer, correspond to zones of relatively deeper or thinner clouds. Deeper clouds correspond to areas of drizzle.

• Temperature (K): the ‘free-air’ temperature at the height that follows the terrain. This is not the same as true surface temperature which has surface radiational heating included.

Background• Current Premise: Moisture and Temperature in winter

has the primary effect on SNC occurrence later in the following late spring.

• Current Premise: Moisture in preceding summer from marine stratus has secondary effect on SNC distribution.

• However: SNC distribution appears to follow the marine stratus regions of occurrence.

• Our Hypothesis: – Marine stratus distribution (drizzle and fog-related leafwetness

during the warm season (late June-early August) sets up the antecedent favorable conditions for SNC growth

– Winter rain distribution is secondary to summertime stratus distribution in specifying the area affected by SNC

Models for SNC Study• Mtnrtcon:

– Horizontal resolution to 2.5 km, but can decrease resolution to 0.2 km (untested).

– Temperature, Dew Point, RH– Wind Speed

• Slopes and peaks• Valleys (direction of wind vs. valley orientation.

– Inversion Base Height• CALMET:

– Resolution to 2 km– Temperature– Wind Speed to 2 km using boundary layer model (Note: cannot

change horizontal or vertical resolution)– Moisture and VV values are calculated but output not currently

available.– Mixing height (corresponds to inversion base height)

Strategy for Analysis

of 2005 Data

• Use Mtnrtcon to analyze specific cases from late June – early August 2005.

– Calculate rain (drizzle) from marine stratus.

– Calculate Tmin and Tmax for the sample days.

What CALMET and Mtnrtcon show about conditions relevant to growth of SNC

• Use CALMET and Mtnrtcon on the 10am LST forecast valid time.

• Marine stratus flag:– Where mixing height<= 1200 m– Where 10am temps are relatively cool, e.g. 283-293K

• Marine drizzle flag:– Where marine stratus flag=yes– Where Wspd<=7 mph– Where mtnrtcon shows 3hr rain>.005.

• 10am Temperature from either CALMET or Mtnrtcon during periods of mtnrtcon rain>.005