Transcript Document

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:
– 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 is collected according to protocol
Sample taken to DDDI Extension Unit
Does Sample require further testing?
Yes
No
Sample is sent to U of I Plant Clinic
Continue to submit suspicious samples
Sample Submission Flow Chart,
cont.
Sample is sent Overnight Delivery Until Confirmation in IL
University of Illinois Plant Clinic
1401 W. St. Mary's Road
Urbana IL 61802
Does sample require further testing?
Yes
Sample sent to
USDA/APHIS Beltsville MD
IF Sample positive for
P. pachyrhizi
Action taken by Federal and
State Agencies
Grower receives instructions
on further action
No
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