Asian Soybean Rust: Scouting

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Asian Soybean Rust Scouting Sampling in
Illinois

• University of Illinois
• State Soybean Rust Taskforce
• Suzanne Bissonnette,
• IPM Educator

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Brand New EditionsBe ready with effective
scouting
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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

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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.

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Rust Severity Assessment Key
A actual amount of tissue occupied by pustules
(Cobb scale) B equivalent damage to leaf
(Modified Cobb) If A18.5 area occupied by
pustules, this is equivalent to B50 damage to
the leaf

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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

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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.

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Soybean Rust Scouting Field Pattern

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

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Foliar Symptoms Soybean Rustnot distinguishing
must look closer
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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

Observe chlorosis
Look at underside of leaves
Observe pustules with hand lens
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Soybean Rust PustulesUnderside leaves, Stems,
Petioles, Cotyledons
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Other Soybean Diseases that Can Be Confused with
Soybean Rust

• Septoria Brown Spot

J. Pataky U of I
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Other Soybean Diseases that Can Be Confused with
Soybean Rust

• Bacterial Pustule
• Bacterial Blight

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Other Soybean Diseases that Can Be Confused with
Soybean Rust

• Downy Mildew

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Hosts of Soybean Rust (gt90)

• 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 poinciana
• Wild hosts
• Kudzu, sweet clover

Kudzu infected with soybean rust
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Kudzu population Distribution and Rust
detections December 6, 2004
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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.

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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.

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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.

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Sample Action Plan Submission Flow Chart
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Sample Submission Flow Chart, cont.
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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

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Acknowledgements

• Presentation by S. Bissonnette, D. Bowman, D.
  Malvick, M. Montgomery
• Acknowledge slides jpgs from G. Hartman, M.
  Miles, USDA-ARS, R. Frederick, M. Palm and
  University of Illinois Extension