Herbicide Modes of Action and Applications
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2,4-D - Interfere with auxin function
Site of Action (2,4-D) - Synthetic auxin
Translocation (2,4-D) - Symplastic
Application type (2,4-D) - Foliar-applied
Chemical family (2,4-D) - Phenoxy
Effect on susceptible plants (2,4-D) - Unregulated growth in broadleaf plants, which
causes damage to vascular tissue
Use in weed management programs (2,4-D) - Control of broadleaf weeds in grass crops
Notable characteristics (2,4-D) - Prone to vapor drift, some formulations are especially
susceptible to vapor drift. Injury first appears as twisting of stems and leaf cupping
Atrazine - Inhibition of photosynthesis
Site of Action (Atrazine) - Inhibition of photosynthesis at Photosystem (PS) II site A
Translocation (Atrazine) - Apoplastic
Application type (Atrazine) - Foliar & soil-applied
Chemical family (Atrazine) - Triazine
Effect on susceptible plants (Atrazine) - Binds with Photosystem II to inhibit electron
transfer. This prevents production of ATP and NADPH used in carbon fixation (Calvin cycle). Also
leads to the production of Reactive Oxygen Species that damage cellular membranes.
Use in weed management programs (Atrazine) - If foliar-applied, surfactant must be
added to tank. Provides control of broadleaf and grass weeds in grass crops including corn,
sorghum and some turf scenarios.
, Notable characteristics (Atrazine) - Resistance to atrazine is prevalent in some cropping
systems/regions. Historically important herbicide because, prior to atrazine development, grass
weeds were becoming a significant problem in grass crops (over-reliance on 2,4-D)
Bentazon - Inhibition of photosynthesis
Site of Action (Bentazon) - Inhibition of photosynthesis at Photosystem (PS) II site B
Translocation (Bentazon) - Apoplastic
Application type (Bentazon) - Foliar-applied
Chemical family (Bentazon) - Benzothiadiazole
Effect on susceptible plants (Bentazon) - Binds with Photosystem II to inhibit electron
transfer. Binds at a site away from the site used by atrazine and tebuthiuron. Bentazon
eventually limits carbon fixation. Also, this leads to the production of Reactive Oxygen Species
that damage cellular membranes.
Use in weed management programs (Bentazon) - Foliar-applied herbicide with no soil
activity. Effective on tough broadleaf weeds and sedges. Used for weed control in crops
including in wheat, barley, corn, sorghum, turf, peanut & beans. These crops are able to
metabolize Bentazon.
Notable characteristics (Bentazon) - Fast acting on susceptible plants. Injury often
appears like contact herbicide.
Clomazone - Inhibition of pigment (carotenoid) biosynthesis
Site of Action (Clomazone) - Inhibition of 1-deoxy-D-xyulose-5-phosphate synthase (DXS)
Translocation (Clomazone) - Symplastic
Application type (Clomazone) - Soil-applied
Effect on susceptible plants (Clomazone) - Inhibits enzyme involved with the production
of carotenoids. Without carotenoids, plants have reduced capacity for dissipating energy from
excess light. This leads to the production of Reactive Oxygen Species that damage cellular
membranes. Affected plants appear 'bleached'.
Use in weed management programs (Clomazone) - Soil applied herbicide that can control
grass and broadleaf weeds in a variety of crops, many vegetable crops. Often applied just prior
to planting. Does not require mechanical incorporation.
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2,4-D - Interfere with auxin function
Site of Action (2,4-D) - Synthetic auxin
Translocation (2,4-D) - Symplastic
Application type (2,4-D) - Foliar-applied
Chemical family (2,4-D) - Phenoxy
Effect on susceptible plants (2,4-D) - Unregulated growth in broadleaf plants, which
causes damage to vascular tissue
Use in weed management programs (2,4-D) - Control of broadleaf weeds in grass crops
Notable characteristics (2,4-D) - Prone to vapor drift, some formulations are especially
susceptible to vapor drift. Injury first appears as twisting of stems and leaf cupping
Atrazine - Inhibition of photosynthesis
Site of Action (Atrazine) - Inhibition of photosynthesis at Photosystem (PS) II site A
Translocation (Atrazine) - Apoplastic
Application type (Atrazine) - Foliar & soil-applied
Chemical family (Atrazine) - Triazine
Effect on susceptible plants (Atrazine) - Binds with Photosystem II to inhibit electron
transfer. This prevents production of ATP and NADPH used in carbon fixation (Calvin cycle). Also
leads to the production of Reactive Oxygen Species that damage cellular membranes.
Use in weed management programs (Atrazine) - If foliar-applied, surfactant must be
added to tank. Provides control of broadleaf and grass weeds in grass crops including corn,
sorghum and some turf scenarios.
, Notable characteristics (Atrazine) - Resistance to atrazine is prevalent in some cropping
systems/regions. Historically important herbicide because, prior to atrazine development, grass
weeds were becoming a significant problem in grass crops (over-reliance on 2,4-D)
Bentazon - Inhibition of photosynthesis
Site of Action (Bentazon) - Inhibition of photosynthesis at Photosystem (PS) II site B
Translocation (Bentazon) - Apoplastic
Application type (Bentazon) - Foliar-applied
Chemical family (Bentazon) - Benzothiadiazole
Effect on susceptible plants (Bentazon) - Binds with Photosystem II to inhibit electron
transfer. Binds at a site away from the site used by atrazine and tebuthiuron. Bentazon
eventually limits carbon fixation. Also, this leads to the production of Reactive Oxygen Species
that damage cellular membranes.
Use in weed management programs (Bentazon) - Foliar-applied herbicide with no soil
activity. Effective on tough broadleaf weeds and sedges. Used for weed control in crops
including in wheat, barley, corn, sorghum, turf, peanut & beans. These crops are able to
metabolize Bentazon.
Notable characteristics (Bentazon) - Fast acting on susceptible plants. Injury often
appears like contact herbicide.
Clomazone - Inhibition of pigment (carotenoid) biosynthesis
Site of Action (Clomazone) - Inhibition of 1-deoxy-D-xyulose-5-phosphate synthase (DXS)
Translocation (Clomazone) - Symplastic
Application type (Clomazone) - Soil-applied
Effect on susceptible plants (Clomazone) - Inhibits enzyme involved with the production
of carotenoids. Without carotenoids, plants have reduced capacity for dissipating energy from
excess light. This leads to the production of Reactive Oxygen Species that damage cellular
membranes. Affected plants appear 'bleached'.
Use in weed management programs (Clomazone) - Soil applied herbicide that can control
grass and broadleaf weeds in a variety of crops, many vegetable crops. Often applied just prior
to planting. Does not require mechanical incorporation.
