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May 2025Archived

 

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Herbicide Symptoms: Page

Unknown Mode of Action

This category contains miscellaneous products for which the mode of action and family are unknown. These herbicides are used in field crops, orchards, aquatic settings, vegetation management, and general pest control.
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Protoporphyrinogen Oxidase (PPO) Inhibitors

Protoporphyrinogen oxidase (PPO) is an enzyme in the chloroplast cell that oxidizes protoporphyrinogen IX (PPGIX) to produce protoporphyrin IX (PPIX). PPIX is important because it is a precursor molecule for both chlorophyll (needed for photosynthesis) and heme (needed for electron transfer chains).
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Glutamine Synthesis Inhibitors

Glufosinate is the only commercialized glutamine synthetase herbicide in the United States. Glufosinate belongs to phosphinic acid chemistry. It is a broad-spectrum postemergent herbicide that controls most annual grasses and broadleaves.
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Lipid Synthesis Inhibitors

(not ACCase Inhibition) Herbicides in this mode of action are most effective on annual grasses and some broadleaf weeds. In general, these herbicides are applied preplanting or preemergence and incorporated into the soil.
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Long Chain Fatty Acid Inhibitors

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.
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Microtubule Assembly Inhibitors

Microtubule Inhibitors are generally applied preemergence to control annual grasses and some broadleaf weeds in many crops and turf grass. These herbicides are absorbed by both roots and shoots of emerging seedlings but are not readily translocated.
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Photosystem I (PSI) Electron Diverter

PSI Electron Diverters are primarily nontranslocated herbicides that are light activated. These are relatively nonselective chemicals used to control all existing vegetation and as preharvest desiccants. PSI Electron Diverters belong to bipyridylium chemistry.
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Photosystem II Inhibitors

Photosynthetic Inhibitors control many broadleaf and some grass weeds. In general, these herbicides inhibit photosynthesis by binding to D1 proteins of the photosystem II complex in chloroplast thylakoid membranes.
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Acetyl CoA Carboxylase (ACCase) Inhibitors

ACCase Inhibitors are primarily used for postemergence grass control in broadleaf crops. These herbicides are absorbed through the foliage and translocated in the phloem to the growing point, where they inhibit meristematic activity.
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