Herbicide injury from ALS inhibitors including imidazolinones (such as imazapic, imazapyr and several others) and sulfonylureas (including sulfosulfuron, metsulfuron, sulmetron, and others).
- Yellow shoot tips and die-back.
- Yellow, pink or purple veins.
- Shorter internodes.
- “Bottle brushing” roots.
- In woody plants, ALS inhibitors may cause:
- foliar cupping.
- deformed foliage.
- witches brooms.
- general die-bac.
J. Neal CC BY-SA - 4.0
T. Bilderback CC BY-NC-ND - 2.0
Plant Entry and Symptom Expression
Foliar and soil absorbed and translocated. Some ALS herbicides have long residual and may affect nearby plants via root uptake or crops planted into previously treated soils. Selected ALS members provide very broad spectrum control while others are quite narrow. Growth cessation within a week of application, followed by chlorosis of the growing points, then tip necrosis, followed by a general decline and death over a period of 3 to 4 weeks. ALS-resistant crops are widely used.
ALS inhibitor injury may be confused with symptoms from:
- Desiccation – loss of cell turgor pressure; salt accumulation.
- General root decline due to poor soil conditions or soil diseases.
- In woody plants, witches brooms and deformed or cupped foliage may resemble glyphosate drift or auxin herbicide injury.
Herbicide Mode of Action Category
WSSA – 2
HRAC – B
Applied Weed Science: Including the Ecology and Management of Invasive Plants (3rd Edition), Merrill Ross & Carol Lembi, pages 166, 172-173, 175, 242, 246-248
Publication date: Dec. 14, 2015
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