Asian Soybean Rust: Scouting & Sampling in Illinois

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

2. Brand New EditionsBe ready with effective scouting

3. 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

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 Rustnot 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 PustulesUnderside 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 email 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. 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