Scott Isard, Penn State Univ. An assessment of the risk of aerial transport of rust pathogens to the Western Hemisphere and within North America

1. An assessment of the risk of aerial transport
of rust pathogens to the Western Hemisphere
and within North America
Scott A. Isard
Departments of Plant Pathology and Meteorology
Pennsylvania State University
University Park, PA USA 16802
and
Joseph M. Russo
ZedX Inc. Bellefonte, PA 16853
2011 BGRI Technical Workshop, St. Paul, MN: 14 June 2011

2. Question
How frequently are there opportunities for rust
pathogens to be transported:
1. From locations in the Eastern Hemisphere to the
Western Hemisphere
2. From locations in subtropical regions to the
continental interior of North America

3. Aerobiota Transport Process Model
Horizontal Transport
Descent
Takeoff
Earth’s atmosphere and
and Ascent
Landing
Pre- Earth’s surface Impact
conditioning
SOURCE AREA DESTINATION AREA
“opportunities” – consideration of processes that occur in the atmosphere

4. Integrated Aerobiology Modeling System (IAMS)
Synoptic Scale Airflows
Govern Transport Ultraviolet Radiation
Direction and Speed Turbulent
Transport and Survival of Spores Temperature and
Turbulent Diffusion Dilution in the while Airborne Relative Humidity
and Wind Shear Atmosphere
Govern Dilution
Dry Deposition
Due to
Wind and
Vertical Distribution of
Spores in Canopy IAMS Turbulence
Modules
Wet
Canopy Density Deposition
& Structure Deposition of Due to
Escape of Spores Washout
Spores into a
Wind & from Canopy by
Turbulence Crop
Precipitation
Time of Spore Release
Plant Temperature &
Growth Leaf Wetness
Colonization of
Stage of Disease Spore Production
Crop Crop
Weather Growth Stage
Isard et al. 2005 BioScience 55: 851-862.

5. Potential Destination Regions Used in Analysis
Alaska
Aleutian Islands British Columbia Eastern
Canada
Washington & Oregon
U.S. Northeast Coast
California Gulf Coast
U.S. Southeast Coast
Florida
Greater Antilles
Hawaii
Lesser Antilles
Mexico & Central America
Northeastern
South America
Northern Chile
Southeastern
South America
Central Chile
Southern Chile

6. Potential Source Regions Used in Analysis
Alaska United Kingdom
British Columbia Eastern
Canada
Northern China
Washington & Oregon
California Gulf Coast Spain/Morocco
U.S. Southeast Coast
Florida Southern China
Greater Antilles
Hawaii
Lesser Antilles Nigeria Philippine Islands
Mexico & Central America Sierra Leone
Cameroon
Northeastern
South America
Angola
Northern Chile
Southeastern
South America
South Africa
Eastern
Central Chile Australia
Southern Chile

7. Parameters and Input Data for IAMS Simulations
- Grid spatial resolution was 0.083 degrees (~ 14 km),
- Vertical resolution was defined by the standard pressure levels (1000, 950, 900,
850, 800, 700, 600, 500 hPa)
- One hr time step.
- National Center for Environmental Prediction–Department of Energy Reanalysis 2
data set for the 1998-2007 period
- Each simulation was initiated for 1 January 1998 with the daily spore production
held constant for the duration of the 10-yr run.
- Nine grid cells (equivalent to about 125,000 ha at the Equator), distributed
throughout a source area, were assumed to have a healthy crop and rust
infection severity of 50%.
- Parameters for the spore release and escape, dispersion, mortality and deposition
modules were those used in a previous soybean rust study (Isard et al. 2007)

8. Frequency of Days with Deposition of Viable Rust Spores in Western
Hemisphere as Simulated by IAMS for 1998-2007
Averaged forforOctober
Averaged for forMarch
Averaged forSeptember
Averaged for February
Averaged for January
Averaged for June
Averaged November
Averaged December
August
April
Year
May
July
0.2/mo
1.3/mo
0.6/mo
0.9/mo
0.4/mo
0.1/mo
0.3/mo
5.0/mo
9.5/mo
1.1/mo
1.3/mo
2.2/mo
5.4/mo
1.2/mo
2.6/mo
0.4/mo
6.5/mo
1.2/mo
0.6/mo
1.5/mo
2.2/mo
1.1/mo
2.5/mo
14.4/mo
11.7/mo
7.0/mo
9.3/mo
9.6/mo
11.6/mo
10.1/mo
5.3/mo
8.7/mo
11.0/mo
6.1/mo
1.8/mo
3.9/mo
3.5/mo
0.6/mo
1.5/mo
1.0/mo
4.1/mo
2.0/mo
0.5/mo
30.8/mo
5.9/mo
13.0/mo
22.3/mo
27.2/mo
29.9/mo
28.1/mo
9.4/mo
0.7/mo
1.1/mo
18.4/mo
12.6/mo
16.6/mo
12.8/mo
0.1/mo
2.2/mo
9.5/mo
11.5/mo
2.7/mo
1.6/mo
3.4/mo
1.3/mo
0.4/mo
1.7/mo
4.1/mo
0.9/mo
0.7/mo
0.4/mo
0.8/mo
0.1/mo
3.6/mo
7.6/mo
6.3/mo
18.0/mo
16.7/mo
13.7/mo
9.4/mo
4.6/mo
2.1/mo
4.7/mo
10.4/mo
8.1/mo
3.3/mo
0.8/mo
0.4/mo
0.7/mo
0.1/mo
0.3/mo
0.2/mo

9. Frequency of Days with Deposition of Viable Rust Spores
from Eastern Hemisphere Source Regions in U.S. & Canadian Destination Regions
0.4/mo
0.1/mo
0.3/mo 0.3/mo
0.1/mo
0.4/mo
0.2/mo
0.1/mo
0.1/mo
0.1/mo
Averaged for All Months in Year 0.1/mo
0.2/mo
Averaged for entire year
Simulated by IAMS for 1998-2007

10. Frequency of Days with Deposition of Viable Rust Spores from
African Source Regions in the Caribbean Islands
Averaged for entire year
4.1/mo
2.4/mo
0.1/mo
4.7/mo
0.03/mo
0.4/mo
0.01/mo
0.01/mo
Simulated by IAMS for 1998-2007

11. Frequency of Days with Deposition of Viable Rust Spores
from African Source Regions in Eastern South America
Trade Winds
> 90% of days
70-90% of days 7.9/mo
70-50% of days
15.9/mo
January
3.2/mo
0.7/mo
0.4/mo
July 7.2/mo
5.5/mo
0.4/mo
0.03/mo
0.03/mo
Averaged for entire year 2.1/mo
> 90% of days
70-90% of days
70-50% of days
Simulated by IAMS for 1998-2007

12. IAMS Model Output
15
14
13
12
11 January 1998
24
23
22
21
20 May 1998

13. Summary of Insights from IAMS Simulations
The frequency of trans-oceanic transport and deposition of viable rust spores in the
Western Hemisphere :
• Africa, tropics – low
• Europe, north of Pyrenees/Alps – low
• Eastern Asia/Australia – low
• Africa, poleward of the tropics – high
relatively short distance
persistent trade winds
Regions in the Western Hemisphere that are influenced by the ITCZ have the highest
likelihood of receiving viable rust spores from the Eastern Hemisphere
• high frequency & high intensity deposition events
Risk of direct aerial transport of viable rust spores to U.S. and Canada - low

14. Question
How frequently are there opportunities for rust
pathogens to be transported:
1. From locations in the Eastern Hemisphere to the
Western Hemisphere
2. From locations in subtropical regions to the
continental interior of North America

15. 30 April 2010
Wind
Speed (m/s)
<5
5-10
>10
The wind speed and directions are averaged for the air layer between the ground
and the height at which air pressure decreases 30 hPa (typically 200 m near
mid-day).

16. Frequency of strong low-level airflows:
South Texas and Delta Regions to designated continental interior regions
1
2
3 0.19 5
Destination Regions
4
1. South Dakota/North
Dakota/southern
Manitoba/southeastern
0.40 Saskatchewan
Wheat Acres 0.33 0.25
2. Minnesota/Iowa/Wisconsin/
0.19
southwestern Ontario
0.23
D 3. Kansas/Nebraska
4. Missouri
T
5. Illinois/Indiana
Source Regions
T. South Texas
D. Mississippi River Delta Region
USDA, National Agricultural Statistics Service
April 2006-2010

17. Frequency of strong low-level airflows:
South Texas and Delta Regions to designated continental interior regions
1
2
3 0.10 5
Destination Regions
4
1. South Dakota/North
Dakota/southern
Manitoba/southeastern
0.28 Saskatchewan
Wheat Acres 0.19 0.18
2. Minnesota/Iowa/Wisconsin/
0.11
southwestern Ontario
0.13
D 3. Kansas/Nebraska
4. Missouri
T
5. Illinois/Indiana
Source Regions
T. South Texas
D. Mississippi River Delta Region
USDA, National Agricultural Statistics Service
May 2006-2010

18. Frequency of strong low-level airflows:
South Texas and Delta Regions to designated continental interior regions
1
2
3 0.06 5
Destination Regions
4
1. South Dakota/North
Dakota/southern
Manitoba/southeastern
0.31 Saskatchewan
Wheat Acres 0.11 0.10
2. Minnesota/Iowa/Wisconsin/
0.10
southwestern Ontario
0.18
D 3. Kansas/Nebraska
4. Missouri
T
5. Illinois/Indiana
Source Regions
T. South Texas
D. Mississippi River Delta Region
USDA, National Agricultural Statistics Service
June 2006-2010

19. Frequency of strong low-level airflows:
South Texas and Delta Regions to designated continental interior regions
1
2
3 0.01 5
Destination Regions
4
1. South Dakota/North
Dakota/southern
Manitoba/southeastern
0.10 Saskatchewan
Wheat Acres 0.04 0.03
2. Minnesota/Iowa/Wisconsin/
0.04
southwestern Ontario
0.07
D 3. Kansas/Nebraska
4. Missouri
T
5. Illinois/Indiana
Source Regions
T. South Texas
D. Mississippi River Delta Region
USDA, National Agricultural Statistics Service
July 2006-2010

20. Frequency of strong low-level airflows:
South Texas and Delta Regions to designated continental interior regions
1
2
3 0.01 5
Destination Regions
4
1. South Dakota/North
Dakota/southern
Manitoba/southeastern
0.12 Saskatchewan
Wheat Acres 0.03 0.02
2. Minnesota/Iowa/Wisconsin/
0.01
southwestern Ontario
0.05
D 3. Kansas/Nebraska
4. Missouri
T
5. Illinois/Indiana
Source Regions
T. South Texas
D. Mississippi River Delta Region
USDA, National Agricultural Statistics Service
August 2006-2010

21. Frequency of strong low-level airflows:
South Texas and Delta Regions to designated continental interior regions
1
2
3 0.03 5
Destination Regions
4
1. South Dakota/North
Dakota/southern
Manitoba/southeastern
0.04 Saskatchewan
Wheat Acres 0.06 0.06
2. Minnesota/Iowa/Wisconsin/
0.04
southwestern Ontario
0.04
D 3. Kansas/Nebraska
4. Missouri
T
5. Illinois/Indiana
Source Regions
T. South Texas
D. Mississippi River Delta Region
USDA, National Agricultural Statistics Service
September 2006-2010

22. Summary of Insights from Airstream Analysis
Strong low-level advection of air northward from the subtropics is
prevalent in North America east of the Rocky Mountains from early April
to mid June providing opportunities for long-distance transport of rust
pathogens into the continental interior.
After mid-June, the number of days with strong low-level advection of
air from south to north across these regions decreases dramatically.

23. Winter Wheat 2010 Soybean 2010
Harvested Acres by U.S. County Harvested Acres by U.S. County
Winter Wheat Crop Calendar for Texas Soybean Crop Calendar for Delta Region
Plant Plant
Head
Harvest Harvest
J F M A M J J A S O N D J F M A M J J A S O N D
Risk of long-distance aerial spread of soybean rust less than wheat rust during the
periods when they could potentially cause crop losses in major North American
production regions