WEED CONTROL IN PASTURE AND RANGELAND
Tim Prather 
Revised December 26, 2007
Controlling undesirable plants on rangeland is an important part of an overall range management program. Undesirable plants use space, moisture, and nutrients that could better be used to produce forage for grazing animals. Poisonous plants are an additional threat to animal health and productivity.
Weed and brush control are not in themselves range management but merely tools available to the manager. Controlling undesirable plants usually requires more intensive management. In most cases, it is futile to try to control undesirable plants without improving management.
Other methods  Methods that have a definite place in range management are: chemical, rotobeating, plowing, disking, railing, chaining, burning, reseeding, and changes in grazing schedules. There are specific sites and reasons for use of the controls listed. Each is effective if used properly. Obtain specific information locally from the county Extension agent or professional range manager.
Safety and toxic hazard  The toxicity of chemicals used in range weed control is low. No evidence is available of direct damage to animals as a result of these herbicides. However, take all precautions to prevent drift and damage to susceptible plants in the vicinity.
Methods of chemical application  Methods of application depend on the species, terrain, and size of the area. In most extensive range weed control projects, the herbicide is applied by aircraft, either fixed-wing or helicopter. However, ground equipment may be used successfully. On small areas, ground or hand equipment may be most economical.
Some pastures contain poisonous plants. Grazing livestock normally do not eat many poisonous plants, but sometimes the composition of plants changes after spraying which make some plants more palatable. Do not graze pastures known to have poisonous plants for at least 3 wk after spraying.
Spot-spray to control perennial weeds in pastures. Follow recommendations to control specific weeds.
Many crops are grazed or used for pasture. When areas not generally defined as pasture are to be grazed, examine the herbicide label to determine what grazing restrictions apply before using the herbicide.
Caution  This handbook is not intended as a complete guide to herbicide use. Before using any chemical, read the label on the container. Before a chemical can be recommended for a specific use, it must be thoroughly tested. The recommendation on the manufacturer’s label, when followed, can prevent many problems arising from the wrong use of a chemical.
 PASTURE AND RANGELAND
•  2,4-D (several products)
Rate  0.71 to 2 lb ae/A
Time  Spray when annual weeds are young, succulent, and actively growing. Treat perennial weeds at the specific growth stage(s) described on the label.
Remarks  Controls many annual, biennial, and perennial broadleaf weeds in rangeland and grass pastures. Also controls certain brushy species, including sagebrush, rabbitbrush, manzanita, and some chaparral species. Deep-rooted perennial weeds and woody plants usually require repeated applications for maximum control. See label for rates for various weed species and for proper application timing.
Caution  Do not apply if spray drift may contact nearby crops or desirable plants or contaminate water for irrigation or domestic use. Do not graze meat animals within 3 days of slaughter. Do not graze dairy animals within 7 days after application. Do not cut hay within 30 days after application. Do not use on bentgrass, alfalfa, clover or other legumes, or on newly seeded pasture. When grass seed production is desired do not apply after heading begins or when grass is in the boot to milk stage. Kills legumes.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  dicamba (Banvel, Vanquish, or Clarity)
Rate  0.25 to 2 lb ae/A
Time  Apply after weeds emerge. Treat annuals when small and actively growing. See label for proper timing and rates on perennials.
Remarks  Controls many annual, biennial, and perennial broadleaf weeds and many woody brush and vine species. Rate depends on weed species and growth stage at time of treatment. Can be applied using water, oil–water emulsions, or sprayable fluid fertilizer as the carrier. May also be applied as a cut-surface treatment to control unwanted trees or to prevent sprouts on cut trees.
Caution  No waiting period between treatment and grazing nonlactating animals (see label for timing restrictions on dairy animals). Meat animals must be removed from treated areas 30 days before slaughter. Rates over 2 lb ai/A may temporarily injure many grass species. Newly seeded grasses (see label) may be injured at rates exceeding 0.75 lb ae/A. Do not exceed 8 lb ae/A per season. Kills legumes.
Site of action  Group 4: synthetic auxin
Chemical family  Benzoic acid
•  fluroxypyr (Starane)
Rate  0.5 to 1.33 pints/A
Time  Apply after weeds emerge. In pastures, use the low rate for weeds less than 4 inches tall and 0.66 pint/A for weeds less than 8 inches tall. Rates up to 1.33 pints/A can be used on Conservation Reserve Program land.
Remarks  Apply to established grasses and to new plantings that are in the two-true-leaf to booting stage of growth.
Caution  No grazing restrictions for lactating dairy animals. Preharvest interval for forage is 7 days. Do not feed treated forage for 2 days before slaughter for meat. Do not exceed 1.33 pints/A of Starane in one growing season.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  fluroxypyr + picloram (Surmount)
Rate  1.5 to 2 pints/A
Time  Apply after weeds emerge. Apply low rate to actively growing, small weeds and up to 2 pints/A when weeds are dense or not growing well.
Remarks  If applying before seeding new grass, wait 3 wk before seeding. To new plantings, apply after grasses are tillering. 
Caution  Lactating dairy animals may not graze or be fed treated forage for 14 days after application. Do not feed treated forage for 3 days before slaughter for meat. No other livestock restrictions. Preharvest interval for hay is 7 days.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (both) pyridine
•  fluroxypyr + triclopyr (PastureGard)
Rate  1.5 to 3 pints/A
Time  Apply after weeds emerge and are still small, not after flower bud stage. Apply low rate to actively growing annual weeds and apply 2 to 3 pints/A to biennial or perennial weed species.
Remarks  Do not use on bentgrass. Wait at least 3 wk after application to reseed. Apply to new plantings after grasses are tillering.
Caution  Do not exceed 8 pints/A in one growing season. Do not feed treated forages to lactating animals during the season of application. Do not feed treated forages for 3 days before slaughter for meat. Preharvest interval for hay is 14 days.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (both) pyridine
• picloram (Tordon)
Rate  0.125 to 1 lb ae/A (0.5 pint to 2 quarts/A)
Time  Treat when weeds are growing actively, in the spring before full bloom, or in late summer or fall. Re-treat in subsequent years as needed.
Remarks  Controls many troublesome perennial and woody weed species including thistles, yellow starthistle, leafy spurge, knapweeds, field bindweed, rabbitbrush, rush skeletonweed, and poison-oak. Rates depend on weed species and plant density. Apply at rates over 0.5 lb ae/A as spot-treatments only and not to exceed 25% of landowner’s acreage in any particular watershed in a single season.
Caution  Most formulations are restricted-use herbicides. Do not apply on or near susceptible crops or desirable plants. Label includes buffer zone restrictions, air temperature limits, and grazing restrictions. Do not contaminate water or where surface water from treated areas can run off to adjacent cropland. Do not apply to inner bank or bottom of irrigation ditches. Do not apply to snow or frozen ground. Do not allow grazing in areas where poisonous plants were sprayed until plants have died, herbicide may increase palatability. Do not spray pastures if the forage legume component is desired. Do not move treated soil. Do not transfer livestock onto crop areas for at least 7 days after grazing on land treated with picloram. See label for other grazing restrictions.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  triclopyr + 2,4-D (Crossbow)
Rate  Spot treatment—use 1 to 1.5% mixture in water. Broadcast—up to 1.5 gal/A (3 lb ae of 2,4-D and 1.5 lb ae of triclopyr).
Time  Postemergence, to actively growing plants.
Remarks  Controls many woody plants as well as annual and perennial broadleaf weeds.
Caution  No forage may be sold for commercial purposes. 
Site of action  (both) Group 4: synthetic auxin
Chemical family  (triclopyr) pyridine; (2,4-D) phenoxy acetic acid
•  tebuthiuron (Spike)
Rate  0.5 to 4 lb ai/A
Time  May be applied any time.
Remarks  Do not exceed 2 lb ai/A if annual precipitation is less than 20 inches. Controls certain woody species including sagebrush. Treatments become effective after enough rain falls to move the chemical into the root zone where it is absorbed by plants. Applications just before seasonal rains will give the most rapid response. Brush will continue to die for several months after application. During this time woody plants may go through repeated defoliations. A single application is normally effective for several years. Areas treated may be overseeded with grass.
Caution  May slightly and temporarily injure desirable grasses. Minimize injury by applying herbicide when grasses are dormant. Do not apply on field crops, near desirable trees or shrubs, or to areas into which their roots may extend. May seriously injure desirable forage legumes. Rate and annual rainfall affect haying and grazing restrictions; see label. Contact a Dow representative for more details.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  hexazinone (Velpar L)
Rate  Not to exceed 0.66 lb ai/A per season. See label about using “exact delivery handgun.”
Time  Just before or during period of active growth of brush species to be controlled.
Remarks  For control of brush in range and pastures. Not intended for broadcast application but for application to soil at base of plants to be controlled.
Caution  Do not apply to brush standing in water or where desirable trees or shrubs are growing immediately adjacent to weedy plants. Do not cut hay from treated areas. Do not use on marshy or poorly drained sites or on soils classified as clays. Do not apply to snow-covered or frozen ground.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazinone 
•  MCPA (several products)
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 pasture and rangeland, including hoary cress, Canada thistle, and buttercup (multiple applications may be required for buttercup control).
Caution  Do not graze for 7 days after treatment. Do not use this treatment on desirable alfalfa. 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 where grass seed production is desired.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  glyphosate (several products) 
Rate  0.1875 to 3.75 lb ae/A
Time  Annual weeds are best controlled when small and actively growing. Apply to actively growing perennial weeds at or beyond full flower. Results are best if applied in late summer or fall after fruit forms. Fall treatments must be before a killing frost.
Remarks  Controls many annual and perennial weed species before renovating pastures. Rates depend on weed species, stage of growth, and density. Repeat treatments may be necessary to control weeds regenerating from underground parts or seed. May also be applied as a spot treatment or by wiper application to established pastures, but do not treat more than 10% of any acre at one time. Further applications may be made to the same area at 30-day intervals.
Caution  A nonselective herbicide that kills forage plants contacted. Total treatments must not exceed 8 lb ai/A per year. Remove domestic livestock before application. Wait 8 wk after broadcast application and 14 days after spot or wiper application before grazing or harvesting.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  imazapic (Plateau)
Rate  0.0312 to 0.1874 lb ai/A (2 to 12 oz/A)
Time  Annual weeds are best controlled preemergence up to small, actively growing plants. Apply to actively growing perennial weeds at or beyond full flower. Results are best if applied in late summer or fall after fruit forms. Leafy spurge can be sprayed before the latex stops flowing in fall (test by breaking open a stem to see whether latex will ooze from the wound). Russian knapweed and Dalmatian toadflax can be controlled in late fall.
Remarks  Use lower rates (4 to 6 oz/A) for early-season downy brome control. Higher rates (8 to 12 oz/A) applied in late summer or fall are needed to control leafy spurge. Fall to early winter application at rates above 0.125 lb ai/A (8 oz/A) may injure establishing perennial grasses. New plantings of bluebunch wheatgrass (Pseudoroegneria spicata), intermediate wheatgrass (Thinopyrum intermedium), crested wheatgrass (Agropyron cristatum), Bozoiski Russian wildrye (Psathyrostachys juncea), Siberian wheatgrass (Agropyron fragile), and big squirreltail (Sitanion jubatum) have survived preemergent fall application of Plateau.
Caution  Do not cut hay for 7 days after application. Do not exceed 12 oz/A in a calendar year.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  paraquat (Gramoxone Extra or Cyclone)
Rate  0.25 to 0.5 lb ai/A west of Cascades
Time  Apply before or at time of seeding grasses. Apply when weeds are succulent and growth is 1 to 6 inches high. Apply October through December after first fall rains when weeds have emerged and sod has started new growth.
Remarks  Not registered for use in Idaho, eastern Washington, or eastern Oregon. Controls or suppresses emerged broadleaf and grass weeds to permit pasture and range reseeding; also suppresses existing sod. Apply as a band treatment when you want sprayed sod to recover. Apply as a broadcast treatment when existing grass species is undesirable. Add 16 to 32 oz of a nonionic surfactant per 100 gal spray. For best seeding results, apply on moderate to heavily grazed areas. Do not use in areas with heavy sod and weed growth.
Caution  A restricted-use herbicide. Do not graze treated areas until new seedlings are 3 to 6 inches high. Do not combine with liquid fertilizer solutions.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium

breakhere •  clopyralid (Stinger or Transline)
Rate  0.5 to 1.33 pints/A
Time  Apply to young, actively growing weeds. Established grasses are tolerant. Apply to Canada thistle after most basal leaves have emerged but before bud stage.
Remarks  Apply only once in a 12-mo period. Do not allow drift to crops. May be tank-mixed with 2,4‑D. Grasses may be planted any time after application.
Caution  Do not spray pastures if forage legume component is desired. See label restrictions on planting crops into treated areas. Before moving livestock from treated site into sensitive crop areas, allow 7 days of grazing on an untreated pasture.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  clopyralid + 2,4‑D (Curtail)
Rate  2 to 4 quarts/A
Time  Apply when weeds are young and actively growing.
Remarks  Use 2 quarts/A on light to moderate infestations of Canada thistle and knapweeds (spotted and diffuse) in good growing conditions. Use 3 quarts/A for dense infestations or under poor growing conditions. On Russian knapweed, use 3 to 4 quarts/A.
Caution  Do not plant grasses for 30 days after application. Do not use on newly seeded grass areas until grass is well established. Do not use on bentgrass. Do not spray pastures containing desirable forbs, especially legumes, unless injury can be tolerated. Do not use hay or straw from treated area for composting or mulching on susceptible broadleaf crops. Do not graze dairy cattle in treated area for 14 days after application. Remove meat animals from area 7 days before slaughter if pasture was treated less than 2 wk earlier. Do not cut for hay within 30 days after application. Do not use straw or manure from treated areas for compost or mulch.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (clopyralid) pyridine; (2,4-D) phenoxy acetic acid
•  triclopyr ester (Remedy)
Rate  0.25 to 2 lb ae/A
Time  When plants are actively growing.
Remarks  Do not spray pastures containing desirable broadleaf forbs, especially legumes, unless injury to these plants can be tolerated.
Caution  Haying and grazing restrictions vary with application rate and livestock type; see label.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  triclopyr + clopyralid (Redeem R&P)
Rate  1.5 to 4 pints/A
Time  Apply to established grasses when broadleaf weeds are actively growing.
Remarks  Do not spray pastures containing desirable broadleaf forbs, especially legumes, unless injury to these plants can be tolerated. Avoid application when conditions indicate air inversion. Do not apply to newly seeded grasses.
Caution  Do not graze lactating dairy animals or harvest green hay for 14 days after application. Other animals may graze 7 days after application. Remove meat animals 3 days before slaughter.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (both) pyridine
•  aminopyralid (Milestone)
Rate  0.75 to 1.75 oz ae/A (3 to 7 oz/A)
Time  Apply postemergence to actively growing plants or in the fall over senesced Russian knapweed plants or preemergence or postemergence for marestail control.
Remarks  Controls a range of broadleaf weeds, including many in the sunflower and legume families. No restrictions on grazing or hay harvest. Surfactants have similar effects in combination with aminopyralid.
Caution  Do not exceed 7 oz/A of Milestone in 1 yr. Allow 3 days after grazing on aminopyralid-treated forage before moving grazing animals to areas with plants sensitive to aminopyralid. Do not use plant residues that were treated within 3 days before harvest for compost or mulch that will be applied to susceptible broadleaf plants.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  dicamba + 2,4‑D (Weedmaster or Pasturemaster) 
Rate  0.5 to 4 pints product/A
Time  When weeds are actively growing.
Remarks  For pasture, range, and noncropland. Spot spraying rates can go as high as 6 pints/A; see label for weeds controlled at higher rates.
Caution  Do not apply when grass is in boot stage. See label for grazing restrictions.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (dicamba) benzoic acid; (2,4-D) phenoxy acetic acid
•  chlorsulfuron (Telar)
Rate  0.25 to 1.33 oz/A
Time  For perennial weeds, apply at budding or flowering stage or in fall at rosette stage. Apply early in life cycle of annual weeds.
Remarks  Bluegrass, bromes, orchardgrass, and wheatgrasses tolerate rates of 0.25 to 1 oz/A. Fescue, bluestems, lovegrasses, and wildrye tolerate rates of 0.25 to 0.5 oz/A. Apply only to established grasses. Telar applied before flowering can reduce seed head development of cool-season grasses.
Caution  Stressed grasses may be injured. No grazing or harvest restrictions for applications up to 1.33 oz/A. Do not exceed 1.33 oz/A per year. 
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  metsulfuron (Escort  or Cimarron)
Rate  0.33 to 2 oz/A Escort; 0.1 to 1 oz/A Cimarron
Time  Apply postemergence to actively growing weeds.
Remarks  Controls a wide range of broadleaf weeds. For best results, use a nonionic or organosilicone surfactant.
Caution  Consult labels for each product; labels differ significantly. Note restrictions on label for use on fescue, timothy, and ryegrass pastures. After applying 3.33 oz/A, wait 3 days to graze. No grazing restriction at or below 1.66 oz/A. Note recropping restrictions on label. Note restrictions for Cimarron on timothy, fescue, and ryegrass. Grass may be planted 60 to 90 days after application.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  metsulfuron‑methyl + dicamba + 2,4‑D (Cimarron Max)
Rate  0.25 oz/A metsulfuron-methyl + 1 pint/A dicamba + 2,4-D to 1 oz/A metsulfuron methyl + 4 pints/A dicamba + 2,4-D. The label tells how to select the use rate, given weed spectrum and sizes.
Time  Apply pre- or postemergence. Results are best if applied to young, actively growing weeds.
Remarks  Cimarron Max is a co-pack with two components: (1) metsulfuron-methyl and (2) a combination of dicamba and 2,4‑D at 1 lb ai/gal dicamba and 2.87 lb ai/gal 2,4-D.
Caution  Weeds often are less susceptible after exposure to cold weather or drought. 
Site of action  (metsulfuron-methyl) Group 2: acetolactate synthase (ALS) inhibitor; (dicamba and 2,4-D) Group 4: synthetic auxin
Chemical family  (metsulfuron-methyl) sulfonylurea; (dicamba) benzoic acid; (2,4-D) phenoxy acetic acid
•  triasulfuron (Amber)
Rate  0.21 to 0.42 oz ai/A (0.28 to 0.56 oz/A)
Time  Apply postemergence to actively growing weeds. Apply preemergence to downy brome and cheat (see Remarks).
Remarks  Apply in a tank-mix with an appropriate herbicide having another mode of action to control a wide spectrum of broadleaf weeds. Add a nonionic surfactant to the spray mixture. Consult label for tolerant grasses. Apply high rate listed above for preemergent, partial control of downy brome and cheat. 
Caution  Orchardgrass, red fescue, and ryegrasses will likely be injured by triasulfuron. Preharvest interval is 30 days for hay. Note recropping restrictions on label.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  triasulfuron + dicamba (Rave)
Rate  2 to 4 oz/A
Time  Apply postemergence to actively growing weeds.
Remarks  Add a nonionic surfactant to the spray mixture. Consult label for tolerant grasses.
Caution  Wait 60 days after grasses emerge before applying Rave. Orchardgrass, red fescue, and ryegrasses will likely be injured. Clovers and alfalfa also may be injured. After applying, wait at least 30 days to cut for hay or to slaughter meat animals that were exposed, and wait at least 8 days to graze lactating cows.
Site of action  (triasulfuron) Group 2: acetolactate synthase (ALS) inhibitor; (dicamba) Group 4: synthetic auxin
Chemical family  (triasulfuron) sulfonylurea; (dicamba) benzoic acid
•  carfentrazone (Aim)
Rate  0.5 to 2 oz/A
Time  Apply postemergence to small (less than 4 inches tall) actively growing weeds. 
Remarks  Using a nonionic surfactant or crop oil concentrate enhances control. Controls corn spurry, a species not listed on many labels of herbicides used in pasture.
Caution  No preharvest interval required. Allow at least 7 days between applications. Do not exceed three applications or 5.9 oz/A per season.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Triazinone