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Herbicide Residue Injury on Canola
Residue Symptoms on Cotyledons
RESIDUE SYMPTOMS ON COTYLEDONS
| Severe injury symptoms such as purpling or chlorosis, severe size reduction or thickening of cotyledon leaves and petioles often appear at the cotyledon stage. However, cotyledon symptoms must be verified by damage to true leaves and/or meristems to eliminate cold stress as a cause for symptoms. Plants with mild injury to true leaves do not show injury to cotyledons. Plants with this severity of cotyledon injury are unlikely to form true leaves, mature and flower. |  |
| A 2-leaf seedling with normal cotyledons (A) and a severely affected seedling (B) at the same age. |  |
| An unaffected (left) and severely affected cotyledon (right) (A). The affected plant had purpling on the back of the cotyledons, but no size reduction. Inspection of the true leaves of these same plants (B) reveals symptoms consistent with Group 2 herbicide injury. The injured plant (right) has reduced leaf area, is chlorotic and is more cupped than the check plant (left). While short term cold events produce cotyledon injury, they do not reduce true leaf area. |
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