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Classification of the severity of leaf blight disease in P. sylvestris var. mongolica seedlings
| Disease severity | Grading standards | Central value |
|---|---|---|
| I | Less than 10% of the lesion area | 0 |
| II | The lesion area accounts for 10%–20% | 1 |
| III | The lesion area accounts for 20%–30% | 2 |
| IV | The lesion area accounts for 30%–40% | 3 |
| V | The lesion area accounts for 40%–50% | 4 |
