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.