Post emergent herbicides are applied after weeds have emerged from the soil, targeting the leaves and stems of actively growing plants. They are the second half of most weed-control programs: pre-emergent products stop seeds from germinating, while post-emergent products kill the weeds that got through. Understanding the major post-emergent options helps growers and gardeners match the product to the weed.
Post-emergent herbicides fall into several modes of action, including ACCase inhibitors, ALS inhibitors, synthetic auxins, EPSPS inhibitors, photosystem II inhibitors, and PPO inhibitors. Each group controls a different spectrum of weeds and carries different resistance risks. Rotating groups is essential for long-term effectiveness.
Many post-emergent herbicides are selective, meaning they kill certain weed types without harming the crop or turf they are sprayed over. Others are non-selective and kill any plant they contact. The label determines which crops and sites a product can be used on and what weeds it controls.
In this guide, we list common post-emergent herbicides by mode of action and explain what each one controls, how it works, and where it is typically used in agriculture, turf, and home landscapes.
List of Post Emergent Herbicides: 15 Common Options Explained
1. Glyphosate – Non-Selective EPSPS Inhibitor
Glyphosate is a non-selective post-emergent herbicide that inhibits the EPSPS enzyme, blocking the shikimic acid pathway that plants use to produce aromatic amino acids. It is absorbed through foliage and translocated to growing points, killing both top growth and roots. Glyphosate controls grasses, broadleaf weeds, and sedges.
- Powerful Weed Control:Effectively kills over 130 types of weeds and grasses, reaching down to the roots to prevent regrowth. Perfect for driveways, sidewalks, fences, and garden areas.
- Covers Up To 26,000 Square Feet
Glyphosate is widely used for site preparation, fence-line clearing, driveway cracks, and burndown applications before planting. It has no soil residual activity, so it does not prevent new weeds from germinating. It is not selective, so it kills desirable plants on contact.
Resistance to glyphosate has developed in many weed species, including Palmer amaranth, waterhemp, and horseweed. Rotation to other modes of action and use of full labeled rates are important for preserving its effectiveness.
– Kills roots and top growth
– Broad-spectrum control
– No soil residual
– Works on many weed species
– Effective in burndown programs
– Affordable price
– Trusted by land managers
– Non-selective
– Kills desirable plants
– Widespread resistance
– Requires careful application
2. 2,4-D – Selective Synthetic Auxin
2,4-D is a selective post-emergent herbicide in the synthetic auxin group. It mimics natural plant hormones, causing uncontrolled cell division and twisting, which kills susceptible broadleaf weeds without harming most grasses. It is absorbed through leaves and translocated throughout the plant.
- Low, economical use rate of 1 to 4 pints per acre
- Controls many broadleaf weeds & woody plants
2,4-D controls broadleaf weeds like dandelion, plantain, thistle, and bindweed in lawns, pastures, and cereal crops. It is often tank-mixed with other herbicides for broader control. It does not control grasses or sedges.
Resistance to 2,4-D is less common than with some other groups but is increasing. It is a restricted-use product in some formulations, and drift to sensitive broadleaf crops can cause serious damage.
– Selective for broadleaf weeds
– Safe for most grasses
– Absorbed and translocated
– Affordable
– Widely available
– Works in lawns and pastures
– Trusted by land managers
– Drift risk to sensitive crops
– Restricted-use in some areas
– Does not control grasses
– Requires repeat applications
3. Dicamba – Selective Synthetic Auxin
Dicamba is a selective post-emergent herbicide in the synthetic auxin group, similar to 2,4-D but with a different chemical structure. It controls a broad range of broadleaf weeds, including kochia, pigweed, and Canada thistle. It is absorbed through leaves, roots, and stems.
- CROP-SAFE WEED KILLER: This herbicide weed killer targets broadleaf weeds in a variety of crops, including corn, soybean, cotton, sugarcane, and turf. Its fast-acting formula ensures long-lasting results, keeping your fields and pastures clean
- FLEXIBLE FIELD COVERAGE: Compatible with both ground and aerial application equipment, this broadleaf herbicide is easy to apply regardless of your farming setup. Whether treating dense vegetation or large-acreage fields, you can depend on consistent coverage
Dicamba is used in corn, small grains, pastures, and non-crop areas. It has some soil residual activity, which provides extended control of germinating broadleaf weeds. It is often tank-mixed with 2,4-D for broader spectrum control.
Dicamba is volatile and can drift long distances, damaging sensitive crops like soybeans and vegetables. Use of dicamba is regulated in many states, with restrictions on application timing and buffer zones.
– Broad-spectrum broadleaf control
– Some soil residual
– Works with 2,4-D
– Effective on tough weeds
– Trusted in corn and small grains
– Widely available
– Affordable
– Highly volatile
– Long-distance drift risk
– State-regulated use
– Can damage sensitive crops
4. Triclopyr – Selective Synthetic Auxin For Woody Plants
Triclopyr is a selective post-emergent herbicide in the synthetic auxin group that targets woody plants and broadleaf weeds while leaving grasses unharmed. It is absorbed through leaves, stems, and roots, depending on the formulation. It controls brush, vines, and tough broadleaf weeds.
- REVIVE FORESTS AND PASTURES: Triclopyr 4 Herbicide targets & controls woody plants, broadleaf weeds, & brush, making it ideal for restoring pastures and managing unwanted vegetation in forests, rangelands, and industrial sites without harming grasses
- YEAR-ROUND APPLICATION FLEXIBILITY: With flexible application options throughout the year, this broadleaf herbicide offers versatility for a wide range of conditions. Its ester formulation allows for effective absorption through leaves and roots
Triclopyr is used in pastures, rights-of-way, forestry, and non-crop areas. It is available in ester and amine formulations, with the ester form used for basal bark and cut-stump treatments. It is highly effective on invasive species like multiflora rose and Japanese knotweed.
Triclopyr has moderate soil residual activity in some formulations. It can injure desirable broadleaf plants if applied carelessly, so careful targeting is essential in mixed landscapes.
– Controls woody plants
– Safe for grasses
– Multiple formulations
– Effective on invasive species
– Basal bark and cut-stump options
– Widely used in forestry
– Trusted by land managers
– Can injure desirable broadleaf plants
– Some soil residual
– Careful targeting required
– Higher cost than 2,4-D
5. Clopyralid – Selective Synthetic Auxin For Asteraceae
Clopyralid is a selective post-emergent herbicide in the synthetic auxin group that targets weeds in the Asteraceae family, including thistles, knapweeds, and hawkweeds. It is absorbed through leaves and roots and translocated throughout the plant. It leaves most grasses unharmed.
- POST-EMERGENT CONTROL - Thistledown is a full-strength herbicide based on the active ingredient clopyralid and is designed to control actively growing broadleaf weeds and thistle in a range, pasture, and other non-crop areas.
- SELECTIVE WEED KILLER - Weeds controlled by Thistledown include Canada thistle, musk thistle, star thistle, and knapweed. It can also be used to control kudzu, dandelion, and Oxalis.
Clopyralid is used in pastures, rangeland, rights-of-way, and some crops. It is highly effective on Canada thistle, musk thistle, and spotted knapweed. It is often tank-mixed with 2,4-D or picloram for broader spectrum control.
Clopyralid has long soil residual activity that can affect sensitive broadleaf plants, including some legumes and vegetables. Compost made from treated grass clippings has caused damage to garden plants in some cases.
– Highly effective on thistles
– Safe for most grasses
– Absorbed and translocated
– Works in pastures and rangeland
– Long-lasting control
– Reduces repeat applications
– Trusted by land managers
– Long soil residual
– Can affect sensitive plants
– Compost contamination risk
– Restricted in some areas
6. Aminopyralid – Selective Synthetic Auxin For Pastures
Aminopyralid is a selective post-emergent herbicide in the synthetic auxin group that controls broadleaf weeds in pastures and rangeland. It is absorbed through leaves and roots and translocated throughout the plant. It is effective on thistles, knapweeds, and other Asteraceae species.
- Target Pests: . See Product label for all listed pests.
- For use In: Rangeland, permanent grass pastures, CRP Acres, non-cropland areas, non-irrigation ditch banks, natural areas, and grazed areas in and around these sites. See Product label for complete list.
Aminopyralid is labeled for use in pastures, rangeland, and non-crop areas. It controls a broad spectrum of broadleaf weeds without harming established grasses. Its long soil residual reduces the need for repeat applications.
Aminopyralid has significant soil residual activity and can affect sensitive broadleaf plants for months or years. It is not suitable for use where legumes or sensitive crops will be planted soon after application.
– Broad-spectrum broadleaf control
– Safe for established grasses
– Labeled for pastures
– Long soil residual
– Reduces repeat applications
– Trusted by land managers
– Works in rangeland
– Long soil residual
– Can affect legumes and sensitive crops
– Compost contamination risk
– Grazing and replanting restrictions
7. Atrazine – Selective Photosystem II Inhibitor
Atrazine is a selective post-emergent and pre-emergent herbicide that inhibits photosystem II in susceptible plants. It is absorbed through roots and leaves and translocated to growing points, where it disrupts photosynthesis. It controls many broadleaf weeds and some grasses in corn and sorghum.
- Kills many broadleaf weeds
- Also used in centipede grass
Atrazine is used primarily in corn and sorghum production, where it controls broadleaf weeds and grasses. It has both pre-emergent and post-emergent activity and is often tank-mixed with other herbicides. It is one of the most widely used herbicides in North America.
Atrazine is a restricted-use product and is regulated due to concerns about groundwater contamination. Resistance has developed in several weed species, including pigweed and kochia. It is not registered for use in many residential settings.
– Pre and post-emergent activity
– Effective on many broadleaf weeds
– Works in corn and sorghum
– Widely used and studied
– Affordable
– Trusted in crop production
– Broad-spectrum control
– Restricted-use product
– Groundwater contamination concerns
– Resistance in some weeds
– Not for residential use
8. Metribuzin – Selective Photosystem II Inhibitor
Metribuzin is a selective herbicide that inhibits photosystem II, disrupting photosynthesis in susceptible plants. It has both pre-emergent and post-emergent activity, making it useful for early-season weed control. It controls many broadleaf weeds and some grasses.
- Active Ingredient: Metribuzin 75%
- TARGET PESTS: Annual bluegrass (Poa annua), Bedstraw, Carpetweed, Chickweed, Corn speedwell, Goosegrass, Henbit, Littleseed canarygrass, Parsley-piert, Prostrate knotweed, Rabbitfootgrass, Red deadnettle, Shepherdspurse, Spotted spurge, Spur weed, White clover, Wild mustard and more
Metribuzin is used in soybeans, tomatoes, potatoes, and cereals, depending on the label. It provides post-emergent control of small weeds when applied early. It is often tank-mixed with other herbicides for broader spectrum control.
Metribuzin can cause crop injury if applied when crops are stressed or if rates are too high. It has moderate soil residual activity that contributes to its pre-emergent effect. Resistance has been reported in some weed species.
– Pre and post-emergent activity
– Works in multiple crops
– Effective on small weeds
– Tank-mix flexibility
– Affordable
– Trusted in vegetable production
– Broad-spectrum control
– Crop injury risk
– Requires proper timing
– Some soil residual
– Resistance in some weeds
9. Bentazon – Selective Photosystem II Inhibitor
Bentazon is a selective post-emergent herbicide that inhibits photosystem II in susceptible broadleaf weeds. It is absorbed through leaves and translocated to growing points, where it disrupts photosynthesis. It controls many broadleaf weeds without harming most grasses.
- Powerful Weed Control: Fast-acting bentazon formula targets broadleaf weeds and sedges on contact; controls over 25 weed species including velvetleaf, pigweed, and nutsedge
- Active Ingredient: Contains sodium salt of bentazon 44.0% (equivalent to 4 pounds bentazon per gallon); selective post-emergence liquid concentrate
Bentazon is used in soybeans, corn, peanuts, and rice, depending on the label. It controls cocklebur, pigweed, and Canada thistle, among others. It is often tank-mixed with other herbicides for broader spectrum control.
Bentazon has limited soil residual activity, so it does not prevent new weeds from germinating. It requires good spray coverage for effective control. It is not effective on grasses or sedges.
– Selective for broadleaf weeds
– Safe for most grasses
– Works in multiple crops
– Limited soil residual
– Tank-mix flexibility
– Trusted in soybeans and rice
– Affordable
– Requires good spray coverage
– No grass control
– No pre-emergent activity
– Limited residual
10. Clethodim – Selective ACCase Inhibitor
Clethodim is a selective post-emergent herbicide in the ACCase inhibitor group (Group 1). It is absorbed through grass leaves and translocated to growing points, where it disrupts fatty acid synthesis. It controls annual and perennial grasses without harming broadleaf crops.
Clethodim is used in soybeans, canola, sugar beets, vegetables, and other broadleaf crops. It controls foxtail, barnyardgrass, Johnsongrass, and quackgrass, among others. It requires a crop oil concentrate or non-ionic surfactant for best absorption.
Clethodim does not control broadleaf weeds or sedges. Resistance to Group 1 herbicides has developed in many grass species, so rotation to other modes of action is essential.
– Selective grass control
– Works in broadleaf crops
– Absorbed and translocated
– Controls perennial grasses
– Widely used in soybeans and canola
– Trusted by growers
– Effective on tough grasses
– Group 1 resistance risk
– Requires adjuvant
– No broadleaf control
– Timing critical
11. Sethoxydim – Selective ACCase Inhibitor
Sethoxydim is a selective post-emergent herbicide in the ACCase inhibitor group (Group 1). It is absorbed through grass leaves and translocated to growing points, where it disrupts fatty acid synthesis. It controls annual and perennial grasses in broadleaf crops.
- This selective grass killer is designed to target both annual and perennial grass weeds.
- The product can be applied to around vegetables, gardens, trees, shrubs and ornamentals safely.
Sethoxydim is used in soybeans, canola, vegetables, and ornamental plantings. It controls foxtail, crabgrass, and Bermudagrass, among others. It requires a crop oil concentrate for best absorption and works best on small, actively growing grasses.
Sethoxydim does not control broadleaf weeds or sedges. Like other Group 1 herbicides, resistance is a concern where it is used repeatedly. Rotation with other modes of action is essential.
– Selective grass control
– Works in broadleaf crops
– Absorbed and translocated
– Effective on annual grasses
– Suitable for ornamentals
– Trusted by growers
– Affordable
– Group 1 resistance risk
– Requires adjuvant
– No broadleaf control
– Best on small weeds only
12. Quizalofop – Selective ACCase Inhibitor
Quizalofop is a selective post-emergent herbicide in the ACCase inhibitor group (Group 1). It is absorbed through grass leaves and translocated to growing points, where it disrupts fatty acid synthesis. It controls annual and perennial grasses in broadleaf crops.
Quizalofop is used in soybeans, canola, sugar beets, and vegetables, depending on the label. It controls foxtail, wild oats, and Johnsongrass, among others. It is often tank-mixed with other herbicides for broader spectrum control.
Quizalofop does not control broadleaf weeds or sedges. Group 1 resistance is a concern, so rotation with other modes of action is essential. It requires a crop oil concentrate or non-ionic surfactant for best absorption.
– Selective grass control
– Works in broadleaf crops
– Absorbed and translocated
– Effective on annual grasses
– Tank-mix flexibility
– Trusted by growers
– Widely available
– Group 1 resistance risk
– Requires adjuvant
– No broadleaf control
– Timing critical
13. Fluazifop – Selective ACCase Inhibitor
Fluazifop is a selective post-emergent herbicide in the ACCase inhibitor group (Group 1). It is absorbed through grass leaves and translocated to growing points, where it disrupts fatty acid synthesis. It controls annual and perennial grasses in broadleaf crops.
- TARGET GRASSY WEEDS WITH FAST-ACTING VENDRA II: Vendra II herbicide is formulated with 24.5% fluazifop-p-butyl to selectively target grassy weeds without damaging desirable grass and ornamental plants.
- POWER OVER PROBLEMATIC GRASSY WEEDS: Vendra II acts quickly on many annual and perennial grassy weeds including bermudagrass, barnyardgrass, crabgrass, foxtail, quackgrass, and more. See the product label for complete control list.
Fluazifop is used in soybeans, vegetables, and ornamental plantings. It controls foxtail, crabgrass, and Bermudagrass, among others. It requires a crop oil concentrate for best absorption and works best on small, actively growing grasses.
Fluazifop does not control broadleaf weeds or sedges. Like other Group 1 herbicides, resistance is a concern where it is used repeatedly. Rotation with other modes of action is essential.
– Selective grass control
– Works in broadleaf crops
– Absorbed and translocated
– Suitable for ornamentals
– Effective on annual grasses
– Trusted by growers
– Widely available
– Group 1 resistance risk
– Requires adjuvant
– No broadleaf control
– Best on small weeds only
14. Carfentrazone – Selective PPO Inhibitor
Carfentrazone is a selective post-emergent herbicide in the PPO inhibitor group that causes rapid cell membrane disruption and desiccation in susceptible weeds. It is absorbed through leaves and acts quickly, often within hours of application. It controls many small broadleaf weeds.
- Provides ultra-fast weed control
- Visible results in just 24 hours
Carfentrazone is used in turf, cereals, and non-crop areas. It is often tank-mixed with other herbicides for broader spectrum control. It is particularly effective on small broadleaf weeds like pigweed and lambsquarters.
Carfentrazone has limited soil residual activity and does not control grasses. It requires good spray coverage for effective control and works best on small weeds. It is often used as a burndown partner.
– Fast contact action
– Effective on small broadleaf weeds
– Tank-mix flexibility
– Works in turf and cereals
– Limited soil residual
– Trusted by turf managers
– Burndown partner
– Requires good spray coverage
– No grass control
– Best on small weeds only
– Limited residual
15. Glufosinate – Non-Selective Glutamine Synthetase Inhibitor
Glufosinate is a non-selective post-emergent herbicide that inhibits the enzyme glutamine synthetase, causing ammonia accumulation and rapid cell death. It is absorbed through leaves and acts on contact, with symptoms appearing within hours. It controls grasses, broadleaf weeds, and sedges.
- NON-SELECTIVE BROAD-SPECTRUM CONTROL Provides post-emergence control of a wide range of broadleaf and grassy weeds, including tough and resistant species such as marestail (horseweed).
- EFFECTIVE ON RESISTANT WEEDS Ideal for managing weeds resistant to glyphosate and multiple herbicide modes of action, making it a powerful rotational or rescue treatment.
Glufosinate is used in burndown programs, glufosinate-resistant crops, and non-crop areas. It has no soil residual activity, so it does not prevent new weeds from germinating. It is often used as an alternative to glyphosate for resistant weeds.
Glufosinate requires good spray coverage and works best on small, actively growing weeds. It is less effective on large or stressed weeds than systemic herbicides. Resistance has been reported in a few weed species.
– Fast contact action
– Broad-spectrum control
– Alternative to glyphosate
– No soil residual
– Works in burndown programs
– Effective on resistant weeds
– Trusted by growers
– Non-selective
– Requires good coverage
– Weak on large or stressed weeds
– Some resistance reported
Tips for Using Post Emergent Herbicides Effectively
- Identify the weed first: Confirm the target species before choosing a product. Post-emergent herbicides vary widely in the weeds they control, and applying the wrong product wastes time and money.
- Spray weeds when small and actively growing: Most post-emergent herbicides work best on young, rapidly growing weeds. Delaying application allows weeds to harden off and reduces control.
- Use the right adjuvant: Many post-emergent herbicides require a crop oil concentrate, non-ionic surfactant, or other adjuvant for proper absorption. Check the label for specific recommendations.
- Rotate modes of action: Using the same group repeatedly selects for resistant weeds. Rotate between ACCase inhibitors, ALS inhibitors, synthetic auxins, and other groups across seasons.
- Check crop and site restrictions: Some products are labeled only for specific crops, turf, or non-crop areas. Always confirm the product is registered for your use site.
- Watch weather conditions: Temperature, humidity, and rainfall affect herbicide uptake and effectiveness. Avoid spraying before rain or during temperature extremes.
- Clean sprayers between products: Residues of some post-emergent herbicides can injure sensitive crops. Rinse tanks thoroughly between products and crops.
Frequently Asked Questions
1. What is a post emergent herbicide?
A post emergent herbicide is applied after weeds have emerged from the soil, targeting the leaves and stems of actively growing plants. This contrasts with pre-emergent herbicides, which are applied before weeds germinate.
2. What is the difference between pre-emergent and post-emergent herbicides?
Pre-emergent herbicides form a barrier in the soil that stops weed seeds from germinating. Post-emergent herbicides are applied to weeds that have already emerged and kill them on contact or systemically.
3. What are the most common post emergent herbicides?
Common post-emergent herbicides include glyphosate, 2,4-D, dicamba, triclopyr, clopyralid, clethodim, sethoxydim, quizalofop, fluazifop, carfentrazone, and glufosinate. Each targets a different spectrum of weeds.
4. Are post emergent herbicides safe for lawns?
Some post-emergent herbicides are labeled for use on lawns, including 2,4-D, dicamba, and certain ACCase inhibitors. Always check the label to confirm the product is safe for your turf species and the weeds you are targeting.
5. How long does it take for post emergent herbicides to work?
Contact herbicides like glufosinate and carfentrazone can show symptoms within hours. Systemic herbicides like glyphosate and 2,4-D may take one to three weeks to fully kill the plant. Speed depends on the product, weed species, and conditions.
6. Do post emergent herbicides prevent new weeds from growing?
Most post-emergent herbicides have no soil residual activity and do not prevent new weeds from germinating. Some products, including atrazine and dicamba, have residual activity and provide extended control.
7. Can I mix post emergent herbicides with other products?
Many post-emergent herbicides can be tank-mixed with other herbicides for broader spectrum control, but compatibility varies by product. Always check labels for tank-mix restrictions and follow the label directions.
Conclusion
Post-emergent herbicides are applied after weeds have emerged and target actively growing plants through leaves, stems, or roots. They fall into several modes of action, including ACCase inhibitors, ALS inhibitors, synthetic auxins, EPSPS inhibitors, photosystem II inhibitors, and PPO inhibitors, each with a different weed spectrum and resistance profile.
Selective products like 2,4-D, dicamba, and clethodim kill specific weed types without harming the crop or turf they are sprayed over. Non-selective products like glyphosate and glufosinate kill any plant they contact and are used for site preparation and burndown applications.
Effective use depends on correct weed identification, proper timing, adequate spray coverage, and appropriate adjuvants. Product labels remain the primary source for crop, site, rate, and application restrictions, and local recommendations should be consulted where resistance is a concern.
The most sustainable approach combines post-emergent herbicides with pre-emergent products, crop rotation, cultural practices, and mechanical control. Rotating modes of action and preventing weed seed production help preserve the effectiveness of these important tools for years to come.