Management to Reduce Weed Problems

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

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 year. 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. Hay cannot be moved off farm if treated with Milestone in the preceding 18 months, unless allowed by supplemental labels; see label for details.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

aminopyralid + 2,4-D (Forefront R&P)

Rate 1.5 to 2.6 pints/a

Time Apply when weeds are young and actively growing.

Remarks Use 1.5 to 2 pints/a on common vetch, yellow woodsorrel, and absinth wormwood. Most susceptible species can be controlled with 2 to 2.6 pints/a.

Caution Do not plant grasses for 30 days after application. Do not use on newly seeded grass areas until grass is well established. May suppress smooth bromegrass. Do not spray pastures containing desirable forbs, especially legumes, unless injury can be tolerated. Allow 3 days after grazing before moving animals to areas with desirable sensitive broadleaf plants. 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 weeks earlier. Do not cut for hay within 14 days after application. Do not use straw or manure from treated areas for compost or mulch. Wait one year after application to rotate to cropland.

Site of action (both) Group 4: synthetic auxin

Chemical family (aminopyralid) pyridine; (2,4-D) phenoxy acetic acid

aminopyralid + metsulfuron (Chaparral)

Rate 1 to 3.3 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. In general, 2 oz/a controls most pasture weeds with lower rates (< 2 oz/a) effective on annual weeds and higher rates (>2 oz/a) effective on woody weeds. No restrictions on grazing or hay harvest. Surfactants have similar effects in combination with aminopyralid.

Caution Do not exceed 3.3 oz/a of Chaparral in 1 year. Allow 3 days after grazing on Chaparral-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 aminopyralid Group 4: synthetic auxin; metsulfuron-methyl Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Pyridine

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

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 wild rye 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

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 weeks 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

dicamba (Banvel, Vanquish, or Clarity)

Rate 0.25 to 1 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 non-lactating 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

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 non-cropland. 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

dicamba + diflufenzopyr (Overdrive)

Rate 4 to 8 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 with lower rates used on annual weeds and higher rates on perennial weeds. Will injure desirable legumes. Use a nonionic surfactant or methylated seed oil.

Caution Do not exceed 8 oz/a of Overdrive in a season. Do not plant any crop for 30 days after application. Grazing is possible immediately after application.

Site of action (dicamba) Group 4: synthetic auxin; (diflufenzopyr) Group 19; auxin transport

Chemical family (dicamba) benzoic acid; (diflufenzopyr) semicarbazone

fluroxypyr (Starane Ultra)

Rate 0.4 to 0.7 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 0.7 pints/a can be used on Conservation Reserve Program (CRP) 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 0.7 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 2.5 pints/a (herbaceous) or 3 to 4 pints/a (woody)

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 weeks before seeding. To new plantings, apply after grasses are tillering.

Caution Not registered for use in Oregon. 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 (herbaceous) or 3 to 8 pints/a (woody)

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 weeks 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

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 on contact. Total treatments must not exceed 8 lb ai/a per year. Remove domestic livestock before application. Wait 8 weeks 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

halosulfuron (Sandea)

Rate 0.33 to 1.33 oz/a.

Time Postemergence.

Remarks For control of sedges in range and pastures.

Caution Do not apply more than 1.33 oz/a in a 12 month period.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

hexazinone (Velpar L)

Rate 2.75 to 4.5 pints/a per season.

Time Just before or during period of active growth of brush species to be controlled.

Remarks For control of herbaceous and woody weeds in range and pastures.

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

imazapic (Plateau, Panoramic)

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 imazapic.

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

MCPA (several products)

Rate 0.46 to 0.7 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 re-growth 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

metsulfuron (Escort XP)

Rate 0.33 to 2 oz/a Escort

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. 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 post-emergence. 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

pendimethalin (Prowl H2O)

Rate 1 to 4 lb ai/a (1.1 to 4.2 quarts/a )

Time Apply prior to emergence of weeds.

Remarks Controls annual grasses and some broadleaf weeds as they germinate.

Caution Application rate depends on soil texture; coarse soils require less herbicide. Do not apply more than 4.2 quarts/a in a crop season. Grazing restrictions apply; do not graze before 45 days after application.

Site of action Group 3: microtubule assembly

Chemical family Dinitroaniline

picloram (Tordon 22K)

Rate 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

sulfosulfuron (Outrider)

Rate 0.035 to 0.062 lb ai/a (0.75 to 1.33 oz/a product)

Time Apply in fall after late-summer and early-fall rains.

Remarks Use higher rates if weeds are larger. Controls annual grasses and some annual forbs. Effective when applied to emerged plants. Apply in a solution of 10 to 50 gal/a of water. Add a surfactant at 0.25% by volume.

Caution Outrider controls meadow foxtail. If meadow foxtail is an important forage grass, do not apply Outrider to areas where meadow foxtail is present. Perennial bromes can be reduced in the first season after application. Addition of spring nitrogen can reduce injury.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

tebuthiuron (Spike 20P)

Rate 0.5 to 4 lb ai/a (2.5 to 20 lb/a product)

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

triasulfuron (Amber)

Rate 0.013 to 0.026 lb 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

triclopyr ester (Remedy Ultra)

Rate 1 to 2 pints/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. Can be used for woody weed control; see label for basal, thinline basal and cut stump application instructions.

Caution Haying and grazing restrictions vary with application rate and livestock type; see label. Do not apply more than 2 quarts in one growing season.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

Chemical family Pyridine

triclopyr choline (Vastlan)

Rate 1 to 2 quarts/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 and use at least a spray volume of 10 gal/a.

Caution Do not allow drift to desirable vegetation. Do not apply more than 2 qt/a Vastlan in a growing season. Many forbs (desirable broadleaf plants) can be seriously injured or killed.

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