Download Gray Leaf Spot Severity Diagram (from P. Paul)

Gray Leaf Spot Severity Diagram (from P. Paul)
Fusarium head blight—disease diagram (J.
Engle et al)
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Fusarium head blight—disease diagram (J.
Engle et al.)
Direct estimation of severity,
with aid of diagrams—
Soybean Rust
Pictorial or
graphic
representation
of selected
levels of
severity
Assign a severity value to a specimen based on
closeness of perceived severity of the specimen
to one of the values in the diagram
2
Direct estimation of severity, with aid
of diagrams—Soybean rust
0
1
2
3
4
5
6
7
8
Bayer Scale
0
0-2.5%
2.5-5%
5-10%
10-15%
15-25%
25-35%
35-67.5%
67.5-100%
Assign a
severity value
to a specimen
based on
closeness of
perceived
severity of the
specimen to
one of the
values in the
diagram
Typically, unequal disease class
intervals; major interpolation needed;
USE MID-POINT OF RANGES
Direct estimation of severity, with use of
a disease scale—Soybean rust
“Disease Scale”:
A partition of the continuous
severity values from 0-100%
into a finite number of classes—
a “diagram” without the diagram
A rater observes a
specimen and
assigns it a class
value (typically the
mid-point)
Kemerait et al. (IL)
0 No disease
1 Trace to 5% infection
2 5-15%
3 15 to 35%
4 35 to 67.5%
5 67.5 to 100%
Generic (see Sinclair, …)
0 No Disease (0%)
1 1-10%
2 11-20%
3 21-30%
…
3
Estimation of severity using ordinal
disease rating scales—Soybean rust
Vuong et al.
“Ordinal Rating Scale”:
Ordered categories (classes) of severity
“Classic (from 1923)”
0
No disease
0.75
Very slight disease
1
Slight
2
Moderate
3
Abundant
1 = No symptoms
2 = Isolated plants with very few symptoms (lesions) in the lower canopy
3 = 1 of 15 leaves with symptoms in the lower canopy
4 = Most or all plants with one or more leaves affected in the lower canopy
5 = Most or all plants with many leaves affected on plant, few leaves affected in the mid canopy
6 = Numerous lesions on most leaves in the mid canopy, limited defoliation in lower canopy
7 = Same as 6, but limited defoliation in mid canopy and severe defoliation in lower canopy
8 = Severe defoliation in mid canopy and limited defoliation in upper canopy
9 = Plants completely defoliated
4
Stagonospora nodorum leaf blotch of wheat.
Liu et al. 2004. Phytopathology 94: 1061-1067.
Stripe rust on wheat
Australian Cereal Rust Control Program
5