An Aerobiological Assessment of Soybean Rust
Threat to North America
Scott Isard (UI) & Roger Magarey, Bob Griffin (CPHST/APHIS)
Joe Russo (ZedX) & Stuart Gage (MSU)Glen Hartman & Monte Miles (ARS & NSRL)
World-Wide SBR DistributionFungicide treated field
José Tadashi Yorinori, Embrapa Soja 2003
Untreated field
• potential to be the most destructive foliar disease of soybean in the U.S.
• has caused significant yield losses worldwide. 2003 yield losses in Brazil exceeded 5% of the annual production (Miles et al. 2003)
• Soybean rust resistant / tolerant cultivars unavailable• Only a few fungicides that control the rust are registered for U.S. foliar application on soybean
• Foliar fungicides require frequent applications and thus can add significantly to production costs.
In 2002:• 355,000 U.S farms grew soybean• 72.1 M acres of soybean were harvested• 23% of harvested crops were soybean
USDA ERS
10% yield losses are possible in any U.S. soybean-growing region. In southeastern states where climatic conditions favor the spread, development, and over-seasoning of the disease, 50% losses are conceivable (Yang 1996).
Contributors
• Scott Isard (UI) & Roger Magarey, Bob Griffin (CPHST/APHIS)
• Joe Russo (ZedX) & Stuart Gage (MSU)
• Charlie Main, Thomas Keever (NCSU)
• Glen Hartman & Monte Miles (ARS & NSRL)
Phakospora pachyrhizi• Not seedborne• Moved easily by wind (short and long distance)• Characterized by local epidemics caused by
multi-cyclic foci and copious production of urediniospores
• Very aggressive and yield limiting
Pathways• Natural spread
– Prevailing winds– Land bridge– Extreme weather events
• Trade– Contaminated seed, grain, meal– Human movements
• Unauthorized imports or releases– Smuggled propagative material– Scientific material
Risk FactorsProbability
• Low for meal because of processing• Medium for grain and seed because of;
– projecting substantial increases in volume– difficulty of detection– likelihood of being able to establish
Assessment of relative likelihood that an epidemic will be initiated by SBR spores blown from the current
source region in South America (stratified by U.S. agriculture region and period of year)
Ecological and Environmental
FactorsImpact
Horizontal Transport
Descent and
Landing
Pre-conditioning
Takeoff and Ascent
Aerobiology Process ModelSource Destination
Created an index for each component
1. Spore production (source region)2. Transport (atmosphere)3. Host distribution4. Epidemic development
(destination region)
Created a composite index as product of component indexes
Turbulent Transport and Dilution in the
Atmosphere
Conceptual Model
of Soybean
Rust Transport Process
Synoptic Scale AirflowsGovern Transport
Direction and Speed
Turbulent Diffusion and Wind Shear Govern Dilution
Survival of Spores while Airborne
Deposition of Spores into a Soybean Crop
Dry Deposition Due to
Wind and Turbulence
Wet Deposition
Due to Washout
by Precipitation
Escape of Spores from Canopy
Spore Production Colonization of Soybean Crop
Ultraviolet Radiation
Temperature and Relative Humidity
Soybean Plant Growth
Stage of Disease
Weather
Vertical Distribution of Spores in Canopy
Canopy Density & Structure
Wind & Turbulence
Time of Spore Release
Soybean Crop Growth Stage
Temperature & Leaf Wetness
0 º
2 0 º
4 0 º 4 0 º
2 0 º
0 º
4 0 º6 0 º8 0 º
4 0 º6 0 º8 0 º
VenezuelaGuyana
SurinameFrench Guiana
Brazil
Argentina
Uruguay
Paraguay
Colombia
Equador
Peru
Chile
Bolivia
The Spread of Soybean Rust
in Latin America
Widespread soybean cultivation
Scattered soybean cultivation
0 º
2 0 º
4 0 º 4 0 º
2 0 º
0 º
4 0 º6 0 º8 0 º
4 0 º6 0 º8 0 º
2001
The Spread of Soybean Rust
in Latin America
Widespread soybean cultivation
Scattered soybean cultivation
2001 Initial discovery of soybean rust
0 º
2 0 º
4 0 º 4 0 º
2 0 º
0 º
4 0 º6 0 º8 0 º
4 0 º6 0 º8 0 º
2002
The Spread of Soybean Rust
in Latin America
Widespread soybean cultivation
Scattered soybean cultivation
2001 Initial discovery of soybean rust2002 Confirmed soybean rust infestation area
0 º
2 0 º
4 0 º 4 0 º
2 0 º
0 º
4 0 º6 0 º8 0 º
4 0 º6 0 º8 0 º
2003
The Spread of Soybean Rust
in Latin America
Widespread soybean cultivation
Scattered soybean cultivation
2001 Initial discovery of soybean rust2002 Confirmed soybean rust infestation area2003 Confirmed soybean rust infestation area
0 º
2 0 º
4 0 º 4 0 º
2 0 º
0 º
4 0 º6 0 º8 0 º
4 0 º6 0 º8 0 º
2004
The Spread of Soybean Rust
in Latin America
Widespread soybean cultivation
Scattered soybean cultivation
2001 Initial discovery of soybean rust2002 Confirmed soybean rust infestation area2003 Confirmed soybean rust infestation area2004 Confirmed soybean rust infestation area
0 º
2 0 º
4 0 º 4 0 º
2 0 º
0 º
4 0 º6 0 º8 0 º
4 0 º6 0 º8 0 º
2004
The Spread of Soybean Rust
in Latin America
Widespread soybean cultivation
Scattered soybean cultivation
2001 Initial discovery of soybean rust2002 Confirmed soybean rust infestation area2003 Confirmed soybean rust infestation area2004 Confirmed soybean rust infestation area2004 Likely (unconfirmed) soybean rust infestation area
?
brazil
Perc_Area_planted_Estimate
0.000000
0.000001 - 0.500000
0.500001 - 1.000000
1.000001 - 2.000000
2.000001 - 4.000000
4.000001 - 5.092200
Percent of Brazilian State Area Planted to Soybean
0< 0.50.5 – 1.01.0 – 2.02.0 – 4.04.0 – 6.0
Equator
SBR Source
Strength and Timing
USDA Foreign Agricultural Servicewww.fas.usda.gov/pecad2/highlights/2003/01/Ag_expansion/index.htm
May-June planting dates
Late Nov-Dec planting dates with some double cropping
Calendar Showing Relative P. pachyrhizi Source Strength in South
America108
Divided year into 6 two-month periods based on spore production in South America and U.S. soybean growing
season
Month of YearF M A M J J A S O N DJ
0
106
102
104
Spore
Pro
du
ctio
n
Equatorial BrazilSouthern BrazilComposite
Low risk
Moderate risk
High risk
Very high risk
Release from
current source area
in South America
0
10
1
100
10,000
1,000
Spore
Conce
ntr
ati
on
Height of SBR spore production
(mid-March)
End of SBR major spore production(mid-May)
Start of second peak
of SBR spore
production(mid-July)
Second peak of SBR
spore production(mid-Aug)
(22 years)
Late-March
Mid-May
Mid-July
Late-Aug
Release from
current source area
0
10
1
100
10,000
1,000
Spore
Conce
ntr
ati
on
Distribution after first
week
Height of SBR spore production
(mid-March)
End of SBR major spore production(mid-May)
Start of second peak
of SBR spore
production(mid-July)
Second peak of SBR
spore production(mid-Aug)
Late-March
Mid-May
Mid-July
Late-Aug
Release from
current source area
Late-March
Mid-May
Mid-July
Late-Aug
Distribution after first
week
0
10
1
100
10,000
1,000
Spore
Conce
ntr
ati
on
Distribution after
second week
Height of SBR spore production
(mid-March)
End of SBR major spore production(mid-May)
Start of second peak
of SBR spore
production(mid-July)
Second peak of SBR
spore production(mid-Aug)
Late-March
Mid-May
Mid-July
Late-Aug
Release from
current source area
Late-March
Mid-May
Mid-July
Late-Aug
Distribution after first
week
Late-March
Mid-May
Mid-July
Late-Aug
Distribution after
second week
0
10
1
100
10,000
1,000
Spore
Conce
ntr
ati
on
Distribution after third
week
Height of SBR spore production
(mid-March)
End of SBR major spore production(mid-May)
Start of second peak
of SBR spore
production(mid-July)
Second peak of SBR
spore production(mid-Aug)
2004?
2004
4 0 º 2 0 º 0 º 2 0 º 4 0 º 6 0 º
4 0 º 4 0 º
2 0 º 2 0 º
0 º 0 º
2 0 º
2 0 º 0 º 2 0 º 4 0 º 6 0 º
2 0 º
Ben
i nB
urk
ina F
aso
Cam
ero
on
Cote
d’ Ivoir
eLi
beri
aN
igeri
aB
uru
ndi
Congo,
Dem
Rep
Gabon
Mad
ag
asc
aR
wand
aSouth
Afr
ica
Tan
zania
Ugand
aZ
am
ibia
Zim
babw
e
7
6
5
4
3
2
1
0Th
ousa
nds
of
Hect
are
Harv
est
ed
Soybean Production 2002
In 2003, Brazil harvested 16 Million ha of soybean while South America as a whole harvested 30 M ha.
Source: FAOSTAT Agricultural Data website
What is the likelihood that SBR spores will be blown from Africa to North
America?
South America SBR source strength is at least 1000 time
greater than that of Africa
SBR source region
0
10
1
Spore Concentration
Jan 4 Feb 2
Jun 1 Jul 14
100
1,000
10,000
Release from Current Source Areas in Africa
Spore production period in west Africa (June 1) Spore production period in west Africa (July 14)
Spore production period in southern Africa (Jan 4) Spore production period in southern Africa (Feb 2)
Jan 4 Feb 2
Jun 1 Jul 14
0
10
1
100
10,000
1,000
Distribution After First Week
Spore production period in west Africa (June 1) Spore production period in west Africa (July 14)
Spore production period in southern Africa (Jan 4) Spore production period in southern Africa (Feb 2)
Spore Concentration
0
10
1
100
10,000
1,000
Distribution After Second Week
Spore production period in west Africa (June 1) Spore production period in west Africa (July 14)
Spore production period in southern Africa (Jan 4) Spore production period in southern Africa (Feb 2)
Spore Concentration
0
10
1
100
10,000
1,000
Jan 4 Feb 2
Jun 1 Jul 14
Distribution After Second Week
0
10
1
100
10,000
1,000
Distribution After Third Week
Spore production period in west Africa (June 1) Spore production period in west Africa (July 14)
Spore production period in southern Africa (Jan 4) Spore production period in southern Africa (Feb 2)
Spore Concentration
Dec 1991 – Jan 1992
Estimating the Likelihood of Aerial Transportto U.S. Agricultural Regions
PacificMountain
NorthernPlains
SouthernPlains
DeltaSoutheast
Northeast
Appalachia
Great Lakes
Corn Belt
Counted dots to create a 3 dimensional data matrix:• Agricultural region (10)• Time of year (6 two-month periods)• Year (10 years from 1991-2001)
Spore Production
Calendar
Percentage of County Area Planted to Soybean
0
1 - 10
11 - 20
21 - 30
31 - 40
41 - 60
(average for 2001 & 2002)
U.S. Soybean Production
U.S. Department of AgricultureNational Agriculture Statistics Servicehttp://www.nass.usda.gov:81/ipedb/
NoAK&Hi
Dry_down
225 - 243
244 - 258
259 - 273
274 - 288
289 - 304
NoAK&Hi
Plant_date
130.000000 - 135.000000
135.000001 - 151.000000
151.000001 - 166.000000
166.000001 - 181.000000
May 27 – Jun 27
Planting Dates(most active period)
Harvesting Dates(beginning of harvest)
May 25 – Jun 25
May 25 – Jun 20
May 30–Jun 28
Jun 14-Jul 14May 20 –Jun 10
May 28–Jun 26
May 20–Jun 30
May 20–Jun 30May 30–Jun 25
May 15 – Jun 15
Apr 25 –May25
May 27 – Jun 27
May 15 – Jun
15
May 25 – Jul 1
May 25 – Jun 20
May 18 – Jun 22
May 3 – Jun 14
May 18 – Jun 4
May 20 – Jun 6
May 19 – May 29
May 16 –
Jun 3
May 14 – Jun 2
May 15 – Jun9
May15
– Jun5
May 10 – Jun 7
May18
– Jun3
May15
– Jun20
May 25 – Jun 25
Oct 20
Sep 28
Sep 25
Oct 5
Oct 1Oct 5
Oct 5Oct 5
Oct 10Oct 5
Sep 15
Aug 15 Oct 1
Oct 1
Sep 25Sep 20
Sep 17
Aug 13
Sep 19
Sep 21
Sep 16
Sep 25
Sep 21
Sep 23Sep25
Sep 21
Sep 30
Oct 1
Oct 1
Soybean: Usual Planting and
Harvesting DatesAgricultural Statistics Board
NASS USDA
Percentage of County Area Covered with Kudzu
No data
0
>0 - 2.5
>2.5 – 5.0
>5.0
U.S. Kudzu DistributionCORN SOYBEAN
KUDZU
U.S. Kudzu Distribution
Source: Reports by US extension agents compiled by Darryl Jewett. About 2 million
acres reported
Percentage of County Area Covered with Kudzu
No data
0
>0 - 2.5
>2.5 – 5.0
>5.0
Simple infection model (Wang and Engel 1998) based on a temperature response function scaled to the pathogen’s wetness duration requirements (Tmin = 13 oC, Tmax = 28 oC, Topt = 20 oC, Wmin = 8 hr, Wopt = 12 hr)
Hatched areas are major soybean growing regions
We estimated the number of days that might be expected to be favorable for soybean rust development during June - August from 30 years of daily temperature and leaf wetness data.
Number of years out of last 30 having >15 days with
conditions conducive to infestation
Hatched areas represent major soybean production regions
Calculated probability that a cohort of spores arriving at the beginning of each month would cause an epidemic that year. Average over past 10 years for each U.S. agricultural region.
Soybean Rust Epidemiology Model
Assessment of relative likelihood that an epidemic will be initiated by SBR spores blown from the current
source region in South America (stratified by U.S. agriculture region and period of year)
Ecological and Environmental
FactorsImpact
Horizontal Transport
Descent and
Landing
Pre-conditioning
Takeoff and Ascent
Aerobiology Process ModelSource Destination
Created an index for each component
1. Spore production (source region)2. Transport (atmosphere)3. Host distribution4. Epidemic development
(destination region)
Created a composite index as product of component indexes
Nort
heast
Lake
Sta
tes
Corn
Belt
Nort
hern
Pla
ins
Appala
chia
South
eas t
Delt
a S
tate
s
South
er n
Pla
ins
Mounta
ins
Paci
fic
Dec-Jan
Feb-Mar
Apr-May
Oct-Nov
Jun-Jul
Aug-Sep
Composite Index
0.5
1.0
0.0
Relative risk on a scale of 0 to 1
0
0.5
1.0
0
10
20
0
.2
.4
0
0.5
1.0
0
0.5
1.0
Soybean Rust Epidemic Index
Kudzu Area Sub-Index
Soybean Area Sub-Index
Host Distribution Index
Transport IndexSource Strength
Index
Dec-Jan
Feb-Mar
Apr-May Oct-Nov
Jun-Jul
Aug-Sep
Component Indexes
NE LS CB NP A SE DS GP M P
NE LS CB NP A SE DS GP M P NE LS CB NP A SE DS GP M P
NE = Northeast SE = SoutheastLS = Lake States DS = Delta StatesCB = Corn Belt GP = Great PlainsNP = Northern Plains M = Mountain StatesA = Appalachia P = Pacific States
D-J F-M A-M J-J A-S O-N
Perc
ent
Nort
heast
Lake
Sta
tes
Corn
Belt
Nort
hern
Pla
ins
Appala
chia
South
eas t
Delt
a S
tate
s
South
er n
Pla
ins
Mounta
ins
Paci
fic
Dec-Jan
Feb-Mar
Apr-May
Oct-Nov
Jun-Jul
Aug-Sep
Composite Index
0.5
1.0
0.0
Relative risk on a scale of 0 to 1
Relative likelihood that an epidemic will be initiated by SBR
spores blown from the current source region
in South America
Provides guidance on where and when to scout.