The Horsfall-Barratt scale [1]
is a system used in plant pathology to assess plant diseases where each plant is assigned a numerical value according to the percentage of leaf area showing disease symptoms. The Horsfall-Barratt scale was designed to compensate for human error in estimating the amount of disease present. The scale is as follows:
| Index |
Percent Affected
|
| 1 |
0
|
| 2 |
0 to 3
|
| 3 |
3 to 6
|
| 4 |
6 to 12
|
| 5 |
12 to 25
|
| 6 |
25 to 50
|
| 7 |
50 to 75
|
| 8 |
75 to 87
|
| 9 |
87 to 94
|
| 10 |
94 to 97
|
| 11 |
97 to 100
|
| 12 |
100
|
The scale is often used in modified form with index values from 0–11 or with different numbers of index points.
References
- ^ Horsfall, J. G.; Barratt, R. W. (1945), "An Improved Grading System for Measuring Plant Disease", Phytopathology