Asian Soybean Asian Soybean RustRust

University of IllinoisState Soybean Rust Taskforce

Suzanne Bissonnette, IPM Educator

Soybean Rust PustulesUnderside Leaf

Weather-Based Assessment of Soybean Rust Threat to North America, Final Report to APHIS, 15 July 2004, Scott Isard, et al.

Predicted Spore Deposition by a

Hypothetical Hurricane

As presented in: US Soybean Rust Detection and Aerobiological Modeling, November, 2004,http://www.aphis.usda.gov/lpa/issues/sbr/sbr.html

Map

December 3, 2004

Hurricane “Ivan” the Terrible

Modeled Spore Deposition

Soybean Production Distribution and Rust detections

December 6, 2004

Action Plan for Soybean Rust

• Illinois state rust taskforce plan – http://www.agr.state.il.us/regulation/soybeanrustprogram.pdf

• Collaboration of state, federal, university, private, grower and applicator organizations

• Initial detection, diagnosis, and confirmation– Field DDDI plant clinic national

mycologist notification management

Soybean Rust Identification

Two species differentiated based on microscopic morphological differences in teliospore characteristics

Phakopsora meibomiae (mild)

Phakopsora pachyrhizi (Asian Soybean Rust, severe)

Ono, Buriticá and Hennen - 1992

Cross-section uredia

Cross section telia

Spread of Soybean Rust

Natural –windborne urediniospores produced in large quantities under moderate temperatures and high humidity. Life cycle ~7-10 days, infection to spore production.

Artificial – movement of infected live plants, leaf material, pods, and stems.

Soybean Rust is not seed borne.Soybean Rust will not over

winter on dead plants.

Hosts of Soybean Rust (>90)

Legumes (Papilionoideae) Cultivated Crops:• Soybean Glycine max • Lima & butter bean

Phaseolus lunatus• Green & kidney bean

Phaseolus vulgaris • Cowpea Vigna unguiculata • Pigeon pea Cajanus cajan • Yam bean, jicama

Pachyrhizus erosus

Ornamental plants:• Hyacinth bean,

lupine, • royal poincianaWild hosts: • Kudzu, sweet clover Kudzu infected with soybean rust

Kudzu : Pueraria montana var lobata (Willd.)

Maesen & S. Almeida

Kudzu population

Distribution and

Rust detections

December 6, 2004

Asian Soybean Rust on Kudzu

over wintering host, early inoculum source?

Yield Loss From Soybean Rust Is a

Result Of:• Premature defoliation• Increase in number of unfilled

pods/plant• Decrease in # of seeds/plant• Decrease in seed weight• Decrease in germinability of seed• Yield losses begin at approx. 3%

severity

Management of Soybean Rust, Illinois

Research program• Short-term solutions

– Fungicide evaluations

• Long-term solutions– Host resistance

• Specific resistance• Partial resistance

– Yield stability (tolerance)– Introduction of resistance from other

sources

• Combination of fungicides and resistance

Glen L. Hartman1, Monte Miles1, and Reid Frederick2, 1USDA-Agricultural Research Service,Department of Crop Sciences, National Soybean Research Center University of Illinois, Urbana, IL,2FDWSR, Fort Detrick, Frederick, MD

Breeding Programs Historical Screening of

Germplasm• Initial studies

– 1961 ≈ 2,800 accessions screened in Taiwan (U.S collection)

– 1970 ≈ 4,000 accessions screened in India (U.S. Collection)

– 1975 ≈ 1,675 accessions (MG V-X) screened in Taiwan (AVRDC)

• From these studies, sources of resistance were found and the inheritance of resistance was characterized

GeneOriginal Source

Resistant Susceptible

Year ID (ineffective)

Rpp1 PI200492 Komata

In 73-1*

Tw 72-1

Immune

Tw 80-1 1960-62(1966)

Rpp2 PI230970 In 73-1*

Tw 72-1 Pp 77-1*

Tw 80-1 1972-74 (1978)

Rpp3 PI462312 Ankur

In 73-1*

Tw 72-1Tw 80-1

1973-1975(1977)

Rpp4 PI459025 Bing Nan

Tw 80-2*

Tw 72-1*

In 73-1*

Major Genes for Resistance

& Year They Were Defeated

Evaluation of U.S. And Exotic Germplasm for Resistance to Soybean Rust & Disease Management Strategies

• Determine the resistance/susceptibility of soybean varieties currently grown in the U.S. to soybean rust

• Identify resistance in the germplasm – Evaluate 16,000 accessions in the USDA

National Soybean Collection (Fort Detrick)– Evaluate reported sources of resistance

(Fort Detrick & international locations)– Evaluate yield stability (tolerance)

Frederick, Bonde, Yang & Hartman, UBS Supported)

Fort Detrick Maryland Containment Research

Facilities (secured greenhouse etc.)• Only location incontinental US where Soybean rust researchhas been allowed to

date

Identified Partial Resistance(epidemic is slowed due to fewer pustules

or spores)

EntryPustules

per plant

Pustules per leaf

Pustules at node 7

AGS 129 1,776 41 104

AGS 181 3,849 130 87

GC 82345-20-2

5,934 168 176

GC 82349-6-1

2,108 49 150

KS 8 2,715 76 107

SRE C-56A 803 23 25

SRE C-56E 709 19 29

SRE D-14C 2,159 58 17SRE D-14D 2,100 54 51

Rust Phenotypespustule types for evaluation in greenhouse

or field

• Tan pustule– A fully susceptible reaction

• Reddish brown pustule (RB)– Indicates some type of resistance

Tan Reddish Brown (RB)

Distribution of 174 soybean accessions when placed into six classes after evaluation of soybean rust severity at

four locations in 2002-2003

16

60

31 33

1711

19

42 45

500

25 24 25

36

54

0 05

37

98

33

0

20

40

60

80

100

120

Immune Resistant Moderatelyresistant

Moderatelysusceptible

Susceptible Highlysusceptible

Soybean rust rating class

Num

ber

of

indiv

iduals

ChinaParaguayBrazilMaryland

Significant Variation by Location

Preliminary Summary of Field Evaluations

• Not one soybean accession was found to be resistant at all locations

• Known single genes had less disease severity in some sites, but also TAN and RB lesions at other sites

B. US Commercial Variety Entries

• 940 cultivars were screened in a single plant screen

• 212 were screened an a second single plant screen, with two inoculation dates, 14 and 28 days after planting

• None were resistant

C Stone

Brand New EditionsBe ready with effective scouting

Disease Scouting for Soybean Rust**

• Typical disease patterns– Random spots in field with diffuse

borders **– Field edges– Whole field**– Patterned

•Headlands, historical, mechanical– Low / high spots

** Expect these patterns for rust

Assessment of Disease• Incidence:

– The number of plants (or units) affected by disease with in a population• ie 47 of 100 plants diseased= 47% incidence• ie 34 of 100 leaflets diseased= 34%

incidence

• Severity:– The measure of actual damage done by

disease•Some keys measure severity of the whole

plant•Some keys measure severity on infected

leaves

Assessment of Rust Severity

• Researchers generally assess rust disease as disease severity of key leaves.

• Rust pustules only occupy a maximum of 37% of the area on a leaf. This is equivalent to 100% infection of that leaf.

A= actual amount of tissue occupied by pustules (Cobb scale)

B= equivalent damage to leaf (Modified Cobb)

* If A=18.5% area occupied by pustules, this is equivalent to B=50% damage to the leaf

Rust Severity Assessment Key

*

Disease Scouting for Soybean Rust Incidence• U of I currently recommends

determining incidence rather than severity for scouting protocol.

• Examine 20 plants in 5 random locations in a field.– Note: one plant with any amount of

rust in 100 plants = 1% incidence

Soybean Rust Scouting Field Pattern

• Scout in a zig-zag pattern in the field making observations of 20 plants in 5 locations

Illinois Scouting –“Look Low As You Go”

• When scouting examine the lower quarter of soybean plants– Examine the undersides of leaves for

pustules.

• If you suspect rust– collect 20 leaflets exhibiting symptoms.– Place flat, dry leaflets between paper

towels.– Double bag suspect leaflets in zip lock

bags.– Clearly label sample.

IL Extension Distance Diagnostics

(DDDI Available in all Units in Illinois)

Sample Process• digital images

submitted for you by Unit

• Diagnosis email reply to Unit

• Samples may then require submission to U of I Plant Clinic.

IL Extension Distance Diagnostics

(DDDI Available in all Units in Illinois)

• No fee for DDDI samples.

• Plant Clinic fee ($12.50) paid by ISPOB if sample is pre-screened with DDDI

• Expect to pay overnight shipping prior to detection in state.

Foliar Symptoms Soybean Rust

not distinguishing must look closer

Symptoms & Signs of Soybean Rust

• Look for pustules and chlorosis on undersides of lower leaves before flowering.

• Severity increases with time and rainfall – lesions can develop on all leaves followed by defoliation

Look at underside of leaves

Observe pustules with hand lens

Observe chlorosis

Soybean Rust PustulesUnderside leaves*, Stems, Petioles,

Cotyledons

Other Soybean Diseases that Can Be Confused with Soybean Rust

• Septoria Brown Spot

J. Pataky U of I

Other Soybean Diseases that Can Be Confused with Soybean Rust

• Bacterial Pustule

• Bacterial Blight

Other Soybean Diseases that Can Be Confused with Soybean Rust

• Downy Mildew

Un-treated Strip Between 2 Fields in

South America

What You Need to Know About

Rust Fungicide Types• Protectant

– +/- absorbed– +/- translocated– Prevent

infection or sporulation

– Use before infection

– Strobilurins, chlorothalonils

• Curative– Absorbed– Translocate– Kill fungal

tissue– Use after

infection– Triazoles

Fungicides Registered for Treatment of Soybean Rust or

With EPA Section 18

 

Fungicide ** Trade Name Family Action

       

Chlorothalonil

Bravo Weather Stik, Echo 720 & 90DF

Chloronitriles(Benzonitriles)

Protectant

Azoxystrobin Quadris Strobilurin Protectant

Pyraclostrobin

Headline Strobilurin Protectant

Myclobutanil Laredo EC & EW Triazole Curative

Propiconizole

Tilt, Propimax, Bumper

Triazole Curative

Tebuconazole

Folicur Triazole Curative

**Section 3 compounds in green, others Section 18 (1/19/05)

 

NOTE: only a total of 2 applications of Sec 18 products are allowed in 1 season

Additional Fungicides That Have or May Get EPA Section

18’sFungicide** Trade

NameFamily Action

Pyraclostrobin + Boscalid

Pristine, pending?

Strobilurin + Carboximide

Protectant

Tetraconazole Domark, pending

Triazole Curative

Propiconizole + Trifloxystrobin

Stratego, approved

Triazole + Strobilurin

Curative + Protectant

Azoxystrobin + Propiconizole

Quilt pending(6.2-12 oz) 0.5% COC

Triazole + Strobilurin

Curative + Protectant

NOTE: only a total of 2 applications of Sec 18 products are allowed in 1 season

Fungicides Strategy for Soybean Rust Management in S. America,

S. Africa• General Brazil (J. Yorinori): • Application at first detection • Second spray 15-20 days later for protective

fungicides • 20-25 days later for protective/curative

fungicides.• Timing of the first spray depends on when the first

infection is detected, weather conditions, and mode of action of the fungicide

• General Zimbabwe (C. Levy, M. Miles, G. Hartman):

• Apply first spray soon after flowering• Apply second application 14-20 days later• Third application only in a severe epidemic

Fungicide Spray Recommendations

(lessons from other countries)• Protectant

(strobilurins,chloronitriles): Apply prior to infection. Strobilurins loose effectiveness after 3-5% severity. Strobilurins no more than once /season

• Curative (triazoles): Apply when rust is present. After 10% severity triazoles may not provide full yield protection.

What Should We Do in Illinois?

• Scenario A: • Disease Expected

– Rust expected, not yet present•Apply Protectant Fungicide

(Benzonitriles, Strobilurins)

– Disease still expected now need 2nd spray•Apply Curative (Triazole)

What Should We Do in Illinois?

Scenario B• Disease expected & develops

after 1st application– Disease expected not yet present

•Strobilurin, Benzonitriles

– Disease expected or now present need 2nd spray•Triazole

– Disease still present need 3rd application•Benzonitriles (PHI), Triazole

Prepare Yourself for Soybean Rust Before It

Arrives• Equip sprayers with proper nozzles• Pre-plan fungicide spray program

– Who? How much acreage/day?• Plan to scout “Low as you go”

weekly• Take representative sample• Get it properly identified• Manage resistance to fungicides,

follow label

Acknowledgements:

Presentation by S. Bissonnette, D.

Bowman, D. Malvick, M. Montgomery

Acknowledge slides & jpg’s from G. Hartman, M. Miles, USDA-ARS, Oregon State Univ., R. Frederick, M. Palm, University of Illinois

Extension