| Scale | Description |
|---|---|
| 0 | No symptom spot on the leaf |
| 1 | 1-20% leaf area infected and covered by spot |
| 2 | 21-40% leaf area infected and covered by spot |
| 3 | 41-60% leaf area infected and covered by spot |
| 4 | 61-80% leaf area infected and covered by spot |
| 5 | 80% leaf area infected and covered by spot |