Asian Soybean Asian Soybean Rust: Scouting Rust: Scouting & Sampling in & Sampling in

IllinoisIllinoisUniversity of IllinoisState Soybean Rust Taskforce

Suzanne Bissonnette, IPM Educator

Brand New EditionsBe ready with effective scouting

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

• 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 recommends determining incidence rather than severity for scouting protocol.– Note: one plant with any amount of

rust in 100 plants = 1% incidence

Illinois Scouting –“Look Low As You Go”

• When scouting examine the lower quarter of soybean plants– Examine 20 plants in 5 random

locations in a field.– Examine the undersides of leaves

for pustules.

Soybean Rust Scouting Field Pattern

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

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

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 population

Distribution and

Rust detections

December 6, 2004

Illinois Scouting –“Look Low As You Go”

• 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.

Sample Action Plan & Submission Flow Chart

Sam ple is sent to U of I P lant Clinic

Yes

Continue to subm it suspicious sam ples

No

Does Sam ple require further testing?

Sam ple taken to DDDI Extension Unit

Sam ple is collected according to protocol

Sample Submission Flow Chart, cont.

G row er receives instructionson further action

IF Sam ple positive forP . pachyrhizi

Action taken by Federal andState Agencies

Sam ple sent toUSDA/APHIS Beltsville MD

Yes No

Does sam ple require further testing?

Sam ple is sent Overnight Delivery Until Confirm ation in ILUniversity of Illinois P lant Clinic

1401 W . St. M ary's RoadUrbana IL 61802

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

Acknowledgements:

Presentation by S. Bissonnette, D.

Bowman, D. Malvick, M. Montgomery

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