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

Brand New Editions Be ready with effective scouting

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

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.

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 *

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 Observe chlorosis Look at underside of leaves Observe pustules with hand lens

Soybean Rust Pustules Underside 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 poinciana Wild 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

Sample Submission Flow Chart, cont.

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

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