1. A spatial model for predicting Swiss needle cast distribution and severity Jeff Stone and Len Coop Depertment of Botany and Plant Pathology Oregon State University

2. 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

3. Average disease severity is related to total area affected

4. 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

5. 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 R 2 =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.

6. 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 %. 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

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

8. 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

9. Average needle retention for New Zealand sites

10. Abundance of pseudothecia on one- and two-year-old foliage

11. 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

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

13. 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.

14. 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

15. 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.

16. Using CALMET and MtnRTCon together to specify marine stratus precipitation in summer for Swiss Needle Cast Alan Fox Fox Weather, LLC 9/21/06

17. Sample Products from CALMET Map of Temperature Map of Wind Speed Map of Mixing Height (base of marine inversion)

18. Sample Products from CALMET Wind Direction/Speed (mph)Mixing Height (meters) 24hr forecast valid 08/29/2006 10am PST FIGURE 1.

19. Sample Products from CALMET 24hr Forecast Valid 10am 8/24/2006

20. 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.

21. 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

22. 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)

23. 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.

24. 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