University of California
Herbicide Symptoms

Long Chain Fatty Acid Inhibitors

HRAC Group: K3

WSSA Group: 15

Long Chain Fatty Acid Inhibitors are preemergent herbicides that are used to control annual grasses and some small-seeded broadleaf weeds in a variety of crops. They do not control or seriously damage emerging plants. The primary site of absorption and action of these herbicides on broadleaf species is the roots, while the primary site of absorption and action on grass species is the emerging shoot. Long Chain Fatty Acid Inhibitors are not readily translocated in the plant. Long Chain Fatty Acid Inhibitors include acetamide, chloroacetamide, oxyacetamide, and tetrazolinone herbicides that are currently thought to inhibit very long chain fatty acid (VLCFA) synthesis. These compounds typically affect susceptible weeds before emergence but do not inhibit seed germination.

Injury symptoms: Symptoms on grass plants include failure of the shoot to emerge from the coleoptile or whorl of the plant, giving the plant a buggy-whip appearance. Susceptible grass seedlings often fail to emerge from the soil. Injury symptoms on broadleaf plants include enlarged cotyledons, restricted growth of the true leaves, dark green color, and stunting. Other symptoms on broadleaf plants include leaf crinkling, leaf red coloring, chlorosis, necrosis, and leaf distortion.

Chemistry Group and Common Names of LCFA Inhibitors
Used in the United States

ChemistryCommon Name
Acetamides Napropamide
Chloroacetamides Acetochlor
  Alachlor
  Dimethenamid
  Metolachlor
  S-metolachlor
  Propachlor
Oxyacetamides Flufenacet
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