1. Asian Soybean Rust: Scouting & Sampling in Illinois
University of Illinois
State Soybean Rust Taskforce
Suzanne Bissonnette,
IPM Educator

2. Brand New Editions Be ready with effective scouting

3. Assessment of Disease Incidence: Severity:
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

4. 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.

5. Rust Severity Assessment Key
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 *

6. 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

7. 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.

8. Soybean Rust Scouting Field Pattern
Scout in a zig-zag pattern in the field making observations of 20 plants in 5 locations

9. Foliar Symptoms Soybean Rust not distinguishing must look closer

10. 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

11. Soybean Rust Pustules Underside leaves*, Stems, Petioles, Cotyledons

12. Other Soybean Diseases that Can Be Confused with Soybean Rust
Septoria Brown Spot
J. Pataky U of I

13. Other Soybean Diseases that Can Be Confused with Soybean Rust
Bacterial Pustule
Bacterial Blight

14. Other Soybean Diseases that Can Be Confused with Soybean Rust
Downy Mildew

15. 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 poinciana
Wild hosts:
Kudzu, sweet clover
Kudzu infected with soybean rust

16. Kudzu population
Distribution and
Rust detections
December 6, 2004

17. 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.

18. IL Extension Distance Diagnostics (DDDI Available in all Units in Illinois)
Sample Process
digital images submitted for you by Unit
Diagnosis reply to Unit
Samples may then require submission to U of I Plant Clinic.

19. 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.

20. Sample Action Plan & Submission Flow Chart

21. Sample Submission Flow Chart, cont.

22. 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

23. Presentation by S. Bissonnette, D. Bowman, D. Malvick, M. Montgomery
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