Grass Hay
Bob Parker
Revised October 24, 2008

GRASS HAY
•  2,4-D amine (several trade names)
Rate  0.7 to 2 lb ae/A
Time  Depends on weeds to be controlled. Apply to grass when annual and biennial broadleaf weeds are small and actively growing and established perennials are at bud stage, unless label indicates otherwise.
Remarks  Controls many broadleaf weeds. Application rate depends on weed species and size. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage and before flower stalks become apparent. Spray perennial weeds while they are still seedlings (coming from seed) or wait until bud stage of growth.
Caution  Do not allow drift to desirable vegetation. Do not apply to newly seeded areas until grass is well established. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not cut for hay within 30 days of application. Do not graze lactating dairy cattle in treated areas for 7 days after application. Do not permit animals being finished for slaughter to graze treated fields within 3 days of slaughter.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  MCPA (Clean Crop MCP Amine 4)
Rate  1 to 2 lb ae/A
Time  Apply to annual broadleaf weeds when small and actively growing. Spray perennials in early bud to full bloom stage and during regrowth in fall.
Remarks  Controls certain annual broadleaf and perennial weeds in grass pastures and grass hay.
Caution  Do not graze dairy animals for 7 days after treatment. Do not harvest for hay less than 21 days after application. Do not graze meat animals in treated areas within 7 days of slaughter. Do not use this treatment if alfalfa is present and desirable. Do not use if temporary injury to clovers cannot be tolerated. Do not use on newly seeded areas until grass is well established. Do not use from early boot to milk stage if grass seed production is desired.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  dicamba (Banvel, Rifle, or Clarity)
Rate  0.25 to 2 lb ae/A
Time  Depends on weeds to be controlled. Apply to grass when annual and biennial broadleaf weeds are small and actively growing and established perennials at bud stage of growth unless label indicates otherwise.
Remarks  Controls many broadleaf weeds. Application rate depends on weed species and size. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage and before flower stalks become apparent. Spray perennial weeds while they are still seedlings (coming from seed) or wait until bud stage of growth. There are no haying or grazing restrictions except for lactating dairy animals.
Caution  Do not allow drift onto desirable vegetation. Do not apply to newly seeded areas until grass is well established. Desirable vegetation (including broadleaf plants) can be seriously injured or killed. 
Restrictions on dicamba-treated hay for lactating dairy animals If up to 0.5 lb ae/A (1 pint) was used, delay harvest 37 days; if up to 1 lb ae/A (2 pints) was used, delay harvest 51 days; if up to 2 lb ae/A (4 pints) was used, delay harvest 70 days. Do not graze lactating dairy animals in treated areas for 7 to 40 days, depending on rate after treatment.
Site of action  Group 4: synthetic auxin
Chemical family  Benzoic acid
•  dicamba + 2,4-D (Weedmaster, Pasturemaster), Latigo)
Rate  0.5 to 4 pints/A Weedmaster or Pasturemaster, or 0.33 to 2.5 pints/A Latigo
Time  Depends on target weeds; consult label. In general, apply to grass when annual and biennial broadleaf weeds are small and actively growing and established perennials are at bud stage.
Remarks  Controls broadleaf weeds. Application rate depends on weed species and size. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage and before flower stalks become apparent. Unless label indicates otherwise, spray perennial weeds while they are still seedlings (coming from seed) or wait until bud stage of growth.
Caution  Do not allow spray to drift onto desirable vegetation. Do not apply to newly seeded areas until grass is well established. Many forbs (desirable broadleaf plants) can be seriously injured or killed.  Do not cut for hay for lactating dairy animals within 37 days of application. Do not graze lactating dairy cattle in treated areas for 7 days after application. Do not permit animals being finished for slaughter to graze treated fields within 30 days of slaughter. Note label restrictions on overseeding or reseeding.
Site of action  Group 4: synthetic auxin
Chemical family  (dicamba) nitrile; (2,4-D) phenoxy acetic acid
•  clopyralid (Stinger, Transline, Clopyr Ag)
Rate  0.125 to 0.5 lb ae/A (0.33 to 1.33 pints/A product)
Time  Depends on weeds to be controlled. Apply to grass when annual and biennial broadleaf weeds are small and actively growing and established perennials are at bud stage of growth unless label indicates otherwise.
Remarks  Controls some broadleaf weeds. Application rate depends on weed species and size. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage and before flower stalks appear. Spray perennial weeds while they are still seedlings (coming from seed) or wait until bud stage of growth unless label indicates otherwise. There are no restrictions on haying or grazing after applying Stinger if used alone at labeled rates.
Caution  Do not allow drift to desirable vegetation. Do not apply to newly seeded areas until grass is well established. Do not use plant residues—including hay from treated areas and manure from animals that consumed forage from treated areas—for composting or mulching where susceptible plants may be grown the following season. Do not spread manure from animals that have grazed or consumed forage from treated areas on land for growing susceptible broadleaf crops. Do not exceed 4 pints/A per year.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  clopyralid + 2,4-D (Curtail)
Rate  2 to 4 quarts/A product
Time  Apply to grass when broadleaf weeds are actively growing.
Remarks  Controls many broadleaf weeds. Application rate depends on weeds to be controlled and density of the infestation. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage and before flower stalks become apparent.
Caution  Do not allow drift to desirable vegetation. Do not apply to newly seeded areas until grass is well established. Many forbs (desirable broadleaf plants, particularly legumes) can be seriously injured or killed. Do not cut for hay within 30 days of application. Do not graze lactating dairy cattle in treated areas for 14 days after application. Do not permit animals being finished for slaughter to graze freshly treated fields within 7 days of slaughter. Removal is not needed after 2 wk from application. Do not use hay or straw from treated areas for composting or mulching. Note label restrictions on overseeding or reseeding.
Site of action  Group 4: synthetic auxin
Chemical family  (clopyralid) pyridine; (2,4-D) phenoxy acetic acid
•  triclopyr (Garlon 3A) 
Rate  0.75 to 2 lb ae/A (1 quart to 0.66 gal/A product)
Time  Apply when woody plants and broadleaf weeds are actively growing.
Remarks  Adjust rate for type of vegetation to be controlled. Controls both emerged herbaceous and woody broadleaf plants. To control biennial thistles or other biennial species, apply before flower stalks appear. Add an approved nonionic surfactant to the spray mix.
Caution  Do not allow drift to desirable vegetation. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not allow grazing or harvest green forage for lactating dairy animals from treated areas during the same growing season after application, Withdraw livestock from grazing treated grass at least 3 days before slaughter during the season of application. Do not harvest for hay within 14 days of application.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine 
•  triclopyr + 2,4-D (Crossbow)
Rate  1 to 1.5% solution for spot treatments or up to 1 gal/A product
Time  Apply to grass when broadleaf weeds are actively growing.
Remarks  Do not apply to forage that is to be cut and sold for commercial purposes. Controls many broadleaf weeds and is very effective on a number of woody species. Rate depends on weeds to be controlled. The smaller the annual weeds, the easier they are to control. Spray biennial weeds in the seedling to rosette stage and before flower stalks appear.
Caution  Do not allow drift to desirable vegetation. Do not apply to newly seeded areas until grass is well established. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not harvest for hay 14 days after application. Note haying and grazing restrictions, particularly for lactating dairy cattle on the label. Note label restrictions on overseeding or reseeding.
Site of action  Group 4: synthetic auxin
Chemical family  (triclopyr) pyridine; (2,4-D) phenoxy acetic acid
•  triclopyr + clopyralid (Redeem R&P)
Rate  1.5 to 4 pints/A product
Time  Depends on weeds to be controlled. Apply to grass when annual and biennial broadleaf weeds are small and actively growing and established perennials are at bud stage, unless label indicates otherwise.
Remarks  Use a nonionic surfactant at the surfactant manufacturer’s recommended rate. Controls many broadleaf weeds. Application rate depends on weed species and size. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage and before flower stalks become apparent. Spray perennial weeds while they are still seedlings (coming from seed) or wait until bud stage of growth. Do not exceed 4 pints/A per year.
Caution  Do not allow drift to desirable vegetation. Do not apply to newly seeded areas until grass is well established. Do not use plant residues—including hay from treated areas or manure from animals that consumed forage from treated areas—for composting or mulching where susceptible plants may be grown the following season. Do not spread manure from animals that have grazed or consumed forage from treated areas on land for growing susceptible broadleaf crops. Do not graze or harvest green forage for lactating dairy animals for 14 days after treatment. Do not harvest hay that will be fed to lactating dairy animals until the next growing season. Do not harvest hay for other livestock for 7 days after treatment. Withdraw slaughter animals from grazing or consuming treated hay at least 3 days before slaughter.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  fluroxypyr (Starane) 
Rate  0.09 to 0.125 lb ae/A (0.5 to 0.67 pint/A product)
Time  Apply in spring when broadleaf weeds are actively growing and are less than 8 inches tall.
Remarks  Only weeds emerged at the time of treatment will be controlled. May be applied to bluegrass, bromegrass, fescue, orchardgrass, ryegrass, timothy and sorghum, sorghum-sudan, sudan, and triticale. A second application may be made no less than 14 days after the first. There are no grazing restrictions.
Caution  Do not let spray drift onto desirable vegetation. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not harvest for hay or silage within 7 days of application. Meat animals must be withdrawn from treated forage at least 2 days before slaughter. Do not exceed 0.25 lb ae/A (1.33 pints/A) per growing season.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine 
•  triclopyr + fluroxypyr (PastureGard) 
Rate  0.56 to 1.5 lb ae triclopyr + 0.19 to 0.5 lb fluroxypyr/A (3 to 8 pints/A product)
Time  Apply when weeds are small and actively growing, before the bud stage of growth.
Remarks  Adjust rate for target vegetation. Controls both emerged herbaceous and woody broadleaf plants. To control biennial thistles or other biennial species, apply before flower stalks appear. An agricultural surfactant may be added to improve foliar wetting.
Caution  Do not let spray drift onto desirable vegetation. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not allow grazing or harvest green forage for lactating dairy animals from treated areas during the same growing season after application, Withdraw livestock from grazing treated grass or consuming treated hay at least 3 days before slaughter during the season of application. Do not harvest for hay within 14 days of application. Do not exceed 4 quarts/A of PastureGard per annual growing season.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  aminopyralid (Milestone)
Rate  0.75 to 1.75 oz ae/A (3 to 7 fl oz/A Milestone)
Time  Apply to actively growing weeds. Consult label for specifics.
Remarks  A nonionic surfactant at 1 to 2 quarts/100 gal spray will enhance control under adverse environmental conditions. Controls several broadleaf weeds. Application rate depends on weed species and stage of growth. There are no restrictions on grazing or hay harvest.
Caution  Do not allow drift to desirable vegetation. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Allow at least  3 days of grazing on an untreated pasture before transferring grazing animals from treated areas where sensitive broadleaf crops grow. Do not exceed 7 fl oz/A Milestone per year.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  aminopyralid + 2,4-D (ForeFront) 
Rate  0.06  to 0.11 lb ae aminopyralid + 0.5 to 0.87 lb ae 2,4-D/A (1.5 to 2.6 pints/A product)
Time  Apply to actively growing weeds under conditions favorable for plant growth.
Remarks  Rate depends on target broadleaf weed species. Use a higher rate when growing conditions are less than favorable, or weeds are mature, or weed foliage is tall and dense, or when residual control is important. Adding a high-quality nonionic surfactant, at 0.25 to 0.5 v/v, enhances control.
Caution  Do not let spray drift onto desirable vegetation. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not harvest for hay within 7 days. Allowing at least 14 days after application before harvest provides maximum herbicidal activity. Do not transfer grazing animals from treated areas to areas where sensitive broadleaf crops grow without first allowing 3 days of grazing on untreated pastures. Do not spread manure from animals that have grazed or consumed treated forage within the previous 3 days on land used for growing broadleaf crops.
Site of action  Group 4: synthetic auxin
Chemical family  (aminopyralid) pyridine; (2,4-D) phenoxy acetic acid
•  metsulfuron (Escort and others)
Rate  0.3 to 2 oz ai/A (0.5 to 3.3 oz/A Escort)
Time  Apply to actively growing weeds.
Remarks  Controls a wide range of broadleaf weeds. For best results, use a nonionic or silicone surfactant. No grazing restrictions for any livestock, including lactating animals, with application rates up to and including 1 oz ai/A (1.67 oz/A product). Note grazing restrictions with higher rates. Note restrictions on label for use on timothy, fescue, and ryegrass pastures. Note recropping intervals on the label.
Caution  Do not allow drift to desirable vegetation. Injures or kills desirable forbs.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  triasulfuron (Amber)
Rate  0.21 to 0.35 oz ai/A (0.28 to 0.47 oz/A Amber)
Time  Apply postemergence to actively growing weeds. Apply preemergence for partial downy brome  and cheat control (see remarks).
Remarks  Check label for grasses that can be treated with triasulfuron. Weed control depends on weed species, size at application, growing conditions, and the level of competition from the crop. Weed control may be reduced if weeds are stressed due to drought, temperature extremes, or other factors. Add a nonionic surfactant to the spray mixture. Apply in a tank-mix with an appropriate herbicide having another mode of action to control a wide spectrum of broadleaf weeds and reduce likelihood of sulfonylurea-herbicide resistance. Apply high rate listed above for preemergent, partial control of downy brome and cheat.
Caution  Triasulfuron is likely to injure orchardgrass, red fescue, and ryegrasses. Do not cut for hay within 30 days after application. Do not exceed 0.84 oz/A Amber in a calendar year. Do not apply to irrigated land if tailwater is used on nontarget land. Note recropping restrictions.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  triasulfuron + dicamba (Rave)
Rate  2 to 4 oz/A product
Time  Apply postemergence to actively growing weeds.
Remarks  Add a nonionic surfactant or crop oil concentrate to the spray mixture. Consult label for tolerant grasses.
Caution  Wait 60 days after grasses emerge before applying. Orchardgrass, red fescue, and ryegrasses  will likely be injured. Do not cut for hay for 30 days after application. Do not graze lactating cows until 8 days after application. Note recropping restrictions.
Site of action  (triasulfuron) Group 2: acetolactate synthase (ALS) inhibitor; (dicamba) Group 4: synthetic auxin
Chemical family  (triasulfuron) sulfonylurea; (dicamba) phenoxy acetic acid
•  glyphosate (several trade names)
Rate  Consult label. Several formulations and concentrations are available.
Time  Depends on target weed or brush species. Annual weeds are best controlled when small and actively growing. Apply to perennial weeds at or beyond full flower or in late summer or in fall after seed forms but before a killing frost.
Remarks  Glyphosate controls susceptible grass and broadleaf plants including many desirable grasses and forbs. Use as a spot treatment, treating up to 10% of any acre. Repeat applications can be made in the same area at 30-day intervals. Glyphosate is nonselective and may control all the vegetation present, so consider reseeding treated areas.
Caution  Kills forage plants on contact. Do not allow drift to desirable vegetation. Remove livestock before applying and do not graze or harvest for 14 days after application. Do not exceed 6 lb ae/A or 8 lb ai/A per year.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  carfentrazone (Aim EC) 
Rate  0.008 to 0.031 lb ai/A (0.5 to 2 fl oz Aim EC)
Time  Apply to emerged and actively growing annual broadleaf weeds no more than 4 inches tall or across. May be applied before seeding and up to jointing stage of crop.
Remarks  Add surfactant; see label for mixing and application directions. Apply in at least 10 gal/A of spray solution. See label for control of specific weeds and adjuvant recommendations. There are no harvest or grazing restrictions.
Caution  Do not exceed 0.093 lb ai/A (5.9 fl oz/A Aim EC) or three applications per season.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Triazinone
•  carfentrazone + 2,4-D (Rage D-Tech) 
Rate  0.38 to 1.03 lb ai/A (8 to 32 fl oz/A Rage D-Tech) 
Time  Apply from leaf-leaf stage to boot stage in new plantings and up to the boot stage in established plantings and when weeds are up to 4 to 6 inches tall. 
Remarks  A nonionic surfactant or crop oil concentrate is required. See label for more information on adjuvants and tank-mixes.
Caution  Do not exceed 2.88 lb ai/A (91 fl oz/A Rage D-Tech) or three applications per season. Tank-mixes with EC or ester formulations of other herbicides may increase leaf speckling. Do not apply to foliage wet from dew, rain, or irrigation; crop injury may increase. Do not graze dairy animals for 7 days or cut for hay for 30 days after application. See label for additional restrictions.
Site of action  (carfentrazone) Group 14: protoporphyrinogen oxidase inhibitor; (2,4-D) Group 4: synthetic auxin
Chemical family  (carfentrazone) triazinone; (2,4-D) phenoxy acetic acid
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