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Herbicide Foliar and Residual Injury
Symptoms Similar to Herbicide Carryover Injury - Herbicides - Crop Production - Canola - Plant & Soil Sciences
SYMPTOMS SIMILAR TO HERBICIDE CARRYOVER INJURY
Mild symptoms of herbicide injury may be confused with symptoms caused by cold temperatures or nutrient-defi cient soil. Cold stress symptoms can arise only after a cold temperature event. Recovery will be rapid as temperatures increase. Nutrient stress symptoms are extremely unlikely to occur at the cotyledon stage as nutrient demands are low. A soil test can determine nutrient availability.
COLD TEMPERATURE SYMPTOMS
| Since the 1st and 2nd leaves are of normal size, the purpling observed is not herbicide injury. The purpling is a result of anthocynin production caused by cold temperatures. Purpling may be towards the base, on the leaf margins or may cover entire young leaves of the plant. This symptom will diminish as temperatures increase. |  |
| In this case, cupping was caused by cold temperatures and symptoms quickly diminished as temperatures increased. |  |
| Cupping was caused by a low level herbicide residue. Variation in herbicide carryover means uninjured (red arrow) and injured yellow arrow) plants may be found in close proximity.Cold stress generally causes more uniform damage. |  |
NUTRIENT DEFICIENCY SYMPTOMS
| These plants were grown under wet conditions from the 2-leaf stage and show classic purpling, cupping and chlorosis. Poor aeration to the roots has created nutrient deficiencies. |  |
| These plants were grown in severely sulphur deficient soil and have typical purpling and leaf cupping symptoms. Plants improved with the addition of magnesium sulphate. |  |
| These plants also exhibit symptoms of sulphur deficiency. Other symptoms include; interveinal chlorosis, purpling of the leaf margins, and necrosis. |  |
| Sulphur deficiency on older plants may result in purpling and cupping of axillary or sideshoot leaves. Herbicide carryover symptoms seldom appear at later leaf stages. |  |
