NONCROPLAND AND RIGHT-OF-WAY VEGETATION CONTROL
Bob Parker and Tim Prather
Revised October 27, 2008 
Total vegetation control with soil-residual herbicides is a process in which the addition of chemicals renders the soil unfit for plant growth. Soil-residual herbicides do not kill all animal and microbiological life in the soil, as does a plant pathologist’s soil sterilization.
Keep the following in mind when using soil-residual herbicides:
1.  Know the weeds that are to be eradicated. This is important to determine which chemicals to use.
2.  Know the area where the chemicals are to be used. Adjacent vegetation and terrain are important.
3.  Plan a program. No single herbicide or other weed control practice will solve all weed problems.
Follow precautions when using soil-residual herbicides.
1.  People, animals, or equipment should not move soil from treated area.
2.  Avoid spray drift during application.
3.  Avoid applying residuals where wind or water might move the treated soil.
4.  Some herbicides vaporize easily. Reduce hazard by applying at lower temperatures and use low-volatile formulations.
5.  Do not apply where roots of desirable vegetation may extend into treated area.
6.  Some herbicides are poisonous to animals. Avoid applying these to vegetation, fruit, or seed that might be eaten.
7.  Apply soil-residual herbicides during late fall east of the Cascades to allow winter precipitation to move the herbicide into the soil. In the high-rainfall areas west of the Cascades, apply after the heavy winter rainy season but early enough to ensure adequate moisture to move the herbicide into the soil.
8.  Ensure that these herbicides do not enter sources of irrigation water; some crops are extremely sensitive to some of these herbicides. Severe crop losses have been due to irrigation water contamination. It is permissible to use these herbicides on banks, canals, and streams only if the label specifically permits that use.
Note  Information in this handbook is not intended to be a complete guide to herbicide use. Before using any chemical, you should read the label recommendations on the container. Before a chemical can be recommended for a specific use, it must be thoroughly tested. Following the recommendation on the manufacturer’s label can prevent many problems from the wrong use of a chemical. 
NONCROPLAND AND RIGHT-OF-WAY—Grass and Broadleaf Weed Control
•  asulam (Asulox)
grass and brackenfern control only
Rate  3.34 lb ai/A (1 gal/A) 
Time  Crabgrass, paragrass or Californiagrass—apply before seedheads form; Johnsongrass—apply when grass is 18 inches or taller; western brackenfern—apply when fern is in full frond
Remarks  A nonionic surfactant at 0.25% may be added to the spray solution
Caution  Do not graze treated areas. 
Site of action  Group 18: inhibits DHP synthase steps 
Chemical family  Carbamate
•  borate sodium chlorate or mixtures (several products)
Rate  Refer to specific labels.
Time  Apply either preemergence or postemergence.
Remarks  These two materials are combined in several different proprietary herbicides. Most can be applied either dry or as a spray, depending on the formulation. For rates, application times, use restrictions, and precautions, consult label of each proprietary mixture.
Caution  If used alone, sodium chlorate creates a fire hazard by increasing the flammability of any combustible material. The metallic salts of boron (borates) combined with sodium chlorate act as a fire retardant and overcome most of the fire hazards inherent in sodium chlorate. Sodium chlorate is toxic to livestock, which like its salty taste. Do not let livestock come in contact with treated areas.
Site of action  None generally accepted
Chemical family  Inorganic
•  bromacil + diuron (Krovar I DF)
Rate  4.8 to 9.6 lb ai/A (6 to 12 lb/A)
Time  Fall or late winter east of Cascades, in March or early April west of Cascades.
Remarks  Rain is needed after application for weed control. Use higher rate where deep-rooted, hard-to-kill perennial weeds are dominant. Reduced rates may be used for maintenance retreatment as needed.
Caution  This material has a long soil residual. Do not use in areas where roots of desirable vegetation may extend.
Site of action  (bromacil) Group 5: photosystem II inhibitor; (diuron) Group 7: photosystem II inhibitor
Chemical family  (bromacil) uracil; (diuron) substituted urea
•  dichlobenil (Casoron)
Rate  4 to 8 lb ai/A
Time  Apply during late fall through early spring when temperatures are cool. Thoroughly incorporate into the soil surface through watering-in.
Remarks  For preemergent and early postemergent (less than 2 inches) control only. Use 4 to 6 lb ai/A for annual weeds, 6 to 8 lb ai/A for perennial weeds, and 10 lb ai/A (250 lb/A) for yellow nutsedge. Do not disturb treated areas after applying.
Caution  Do not apply on top of frozen soil.
Site of action  Group 20: inhibits cell wall synthesis Site A
Chemical family  Nitrile
•  diquat (Diquat or Reglone)
Rate  0.25 to 0.5 lb ai/A for broadcast treatments, 0.5 to 1 lb ai/A for spot treatment
Time  Apply when weeds are young.
Remarks  Diquat is a contact herbicide that kills only the tops of most perennial weeds. Use 8 to 16 oz of a nonionic surfactant per 100 gal water.
Caution  A moderately toxic herbicide that requires protective gear for handling and application. Do not let spray contact skin, eyes, or clothing. Do not breathe spray mist.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  diuron (Karmex DF)
Rate  4 to 12 lb ai/A
Time  Apply in fall or late winter east of Cascades and in spring west of Cascades.
Remarks  Use higher rates for perennial weed control, lower rates for annual weed control. (Make maintenance applications on areas previously treated at 6 to 8 lb ai/A.) Does not control certain tap-rooted perennial and biennial weeds such as buckhorn plantain, wild carrot, and dandelion.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  glyphosate
Rate  0.75 to 3.75 lb ae/A
Time  Apply to foliage of actively growing weeds and grasses at growth stage label recommends.
Remarks  Use lower rates for annual weed control, higher rates for perennial weeds. Use enough water carrier for complete coverage but not to the point of runoff. Established perennials may require retreating; glyphosate is highly translocated and has no soil activity. In wick or wiper equipment, mix 1 gal Roundup in 2 gal water to prepare a 33% solution. Operate equipment no faster than 5 mph. Performance may be improved by reducing speed in areas of heavy weed infestations to ensure adequate wiper saturation. Results may be better with two applications made in opposite directions.
Caution  Rain within 12 hr after application may reduce effectiveness. Do not mow or till before treatment. Do not use glyphosate in galvanized or mild steel tanks.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glyphosate + 2,4-D (Landmaster BW)
Rate  108 oz/A product or 1% solution for spot spraying
Time  Apply to foliage of actively growing weeds and grasses at growth stage label recommends.
Remarks  To control labeled annual weeds and suppress perennials on farmsteads, along fence rows, and in dry ditches. For spot spraying, thoroughly cover target weeds but not to point of runoff.
Caution  Do not let spray drift onto desirable vegetation. Control may be reduced if plants are stressed. Heavy dust on foliage or rain or irrigation within 6 hr after application may reduce effectiveness.
Site of action  (glyphosate) Group 9: inhibits EPSP synthase; (2,4-D) Group 4: synthetic auxin
Chemical family  (glyphosate) none generally accepted; (2,4-D) phenoxy acetic acid
•  hexazinone (Velpar L or Velpar DF)
Rate  1 to 3 lb ai/A
Time  Apply before rain to fully activate. Provides some foliar activity.
Remarks  Apply preemergence. Use low rates for annual weed control and high rates for perennial weeds. See label for susceptible weeds, use restrictions, and precautions.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazine
•  hexazinone + sulfometuron (Westar)
Rate  2 to 4 lb product/A
Time  Apply before rain to fully activate. 
Remarks  Apply before or shortly after weeds emerge. Provides some foliar activity. Use the lower rate on coarse soils. Do not tank-mix with bromacil (Hyvar). See label for susceptible weeds, use restrictions, and precautions.
Site of action  (hexazinone) Group 5: photosystem II inhibitor; (sulfometuron) Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  (hexazinone) triazine; (sulfometuron) sulfonylurea
•  imazapic (Plateau)
Rate  0.063 to 0.188 lb ai/A
Time  Apply before or shortly after annual weeds emerge. For perennial weeds, follow label directions.
Remarks  To control labeled annual and perennial weeds. See label for best time for perennial weeds.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
  imazapic + glyphosate (Journey)
Rate  10.7 to 32 oz/A
Time  Apply before or after weeds emerge; see label for specific recommendations.
Remarks  Controls many annual, biennial, and perennial weeds. Effective on downy brome and medusahead rye.
Site of action  (imazapic) Group 2: acetolactate synthase (ALS) inhibitor; (glyphosate) Group 9: inhibits EPSP synthase
Chemical family  (imazapic) imidazolinone; (glyphosate) none generally accepted
•  imazapyr (Arsenal, Contain, or Stalker)
Rate  0.25 to 1.5 lb ai/A
Time  Apply before or soon after weeds emerge.
Remarks  For postemergence control with residual control of many annual and perennial weed species. In most situations, best applied postemergence to vigorously growing weeds.
Caution  Do not apply where chemical may contact roots of desirable trees or plants.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone 
•  isoxaben + trifluralin (Snapshot 2.5TG)
Rate  Consult labels.
Time  Apply before weeds germinate.
Remarks  Controls both annual grass and broadleaf weeds. Areas treated should be free of established weeds. Overhead moisture required to move herbicide into soil.
Site of action  (isoxaben) Group 21: inhibits cell wall synthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor
Chemical family  (isoxaben) benzamide; (trifluralin) dinitroaniline
•  linuron (Lorox)
Rate  1 to 3 lb ai/A
Time  Apply shortly before weed growth begins or at early seedling stage.
Remarks  For established annual weeds, add surfactant at 2 quarts/100 gal spray mixture. Apply when daily temperatures exceed 70°F and before weeds are more than 8 inches high. Best results are with rain or irrigation within 2 wk of application. See label about soil types.
Caution  Do not enter treated area for 24 hr after applying unless wearing protective clothing.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  norflurazon (Solicam DF or Predict)
Rate  1.97 to 3.9 lb ai/A
Time  Apply in fall to early spring before weeds germinate.
Remarks  Adjust rates depending on soil texture and organic matter. Mechanically remove or control existing weeds with a suitable postemergent herbicide.
Site of action  Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family  Pyridazinone
•  organic arsenicals (MSMA or DSMA)
Rate  See labels
Time  See labels
Remarks  These are broad-spectrum contact herbicides with no soil-residual activity. Only the tops of most perennial weeds will be killed. Repeated retreatments are necessary. Use 0.25% of a nonionic adjuvant to enhance weed control.
Caution  Application at temperatures below 70°F usually results in poor weed control.
Site of action  Group 17: not well understood
Chemical family  Organoarsenical
•  oryzalin (Surflan Specialty Herbicide)
Rate  2 to 6 lb ai/A
Time  Apply before weeds germinate and when moisture can move herbicide into the soil.
Remarks  Length of control depends on rate applied. If weeds are present at time of treatment, tank-mix with an approved postemergence herbicide.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  paraquat (Gramoxone Max or Gramoxone Inteon)
Rate  0.6375 to 1 lb ai/A (1.7 to 2.7 pints/A Gramoxone Max) or 0.62 to 1 lb ai/A (2.5 to 4 pints/A Gramoxone Inteon)
Time  Apply when weeds are young and succulent.
Remarks  Paraquat is a contact herbicide that kills only the tops of most perennial weeds. Retreatments are necessary. Add a nonionic surfactant or crop oil concentrate as directed on the Gramoxone labels to spray. Use enough water to thoroughly cover weeds.
Caution  A restricted-use herbicide. Do not use around homes or other areas contacted by children or pets. Do not breathe spray mist. Do not let spray contact skin or clothing.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  pendimethalin (Pendulum)
Rate  2 to 4 lb ai/A
Time  Preemergence grass and broadleaf weed control.
Remarks  Will not control established weeds. Treatments are most effective when it rains within 30 days after application.
Caution  Toxic to fish. Do not apply directly to water or to wetlands.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  prometon (Pramitol)
Rate  10 to 15 lb ai/A
Time  Apply at weed emergence or within 2 to 3 mo after spring growth begins.
Remarks  Prometon has both foliage and root action and has been one of the most effective broad-spectrum herbicides for organic and alkaline soils. Prometon is formulated as a liquid for spray application and as a granular in combination with simazine, borate, and sodium chlorate for spot application.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazine
•  sulfometuron (Oust)
Rate  1 to 6 oz ai/A (1.33 to 8 oz/A)
Time  Apply before or soon after weeds emerge for nonselective control. Rain required to activate herbicide fully.
Remarks  Controls many annual broadleaf weeds, some grasses, and certain perennial broadleaf species. Rates depend on weed species and desired duration of weed control. The 1-oz ai/A rate selectively controls certain grasses. Add a nonionic surfactant at 1 quart/100 gal spray to improve activity.
Caution  If rain is limited, Oust may not satisfactorily control hard-to-kill perennials. Do not apply during periods of intense rain or to water-saturated soils. Do not treat powdery, dry soils and light, sandy soils if it’s unlikely to rain after treatment. Do not let spray drift to adjacent crops.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
NONCROPLAND AND RIGHT-OF-WAY—Broadleaf Weed Control
•  tebuthiuron (Spike 80)
Rate  1 to 4 lb ai/A
Time  Apply in fall east of Cascades and in spring west of Cascades.
Remarks  Use higher rates for perennial weed control, lower rates for annual weed control and maintenance treatments.
Caution  Spike will kill trees, shrubs, and other desirable vegetation if roots extend into the treated area.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  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 specific weeds.
Remarks  Effective on knapweeds, biennial thistles, Canada thistle, perennial sowthistle, horseweed (marestail) and hawkweed. A nonionic surfactant at 1 to 2 quarts/100 gal spray enhances control under adverse environmental conditions. Application rate depends on weed species and stage of growth.
Caution  Do not allow drift to desirable vegetation. Do not exceed 7 fl oz/A Milestone per year.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  bromoxynil (Buctril)
Rate  0.25 to 0.5 lb ai/A
Time  Postemergent, when weeds are actively growing.
Remarks  Apply to broadleaf weeds before four-leaf stage or less than 2 inches high or 1 inch across, whichever comes first. Adding surfactant or crop oil concentrate may improve broadleaf weed burndown under cool, dry conditions.
Caution  Do not allow grazing in treated areas. Do not apply through backpack or hand-held application equipment.
Site of action  Group 6: photosystem II inhibitor
Chemical family  Nitrile
•  chlorsulfuron (Telar)
Rate  0.75 to 2.25 oz ai/A (1 to 3 oz/A)
Time  Apply preemergence or postemergence to weeds. For best results, apply postemergence to young actively growing weeds any time except when ground is frozen.
Remarks  Adequate moisture (rain) is needed to activate herbicide. In postemergence applications, a nonionic surfactant must be added at 1 quart/100 gal spray.
Caution  Agitation is required. Do not apply to soils saturated with moisture or during periods of intense rain. Degree of control and duration of effect varies with amount of chemical applied, soil texture, soil pH, soil organic matter, weed size, rain, and other factors.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  clopyralid (Transline)
Rate  0.09 to 0.5 lb ae/A
Time  After weeds have emerged and, depending on species, up to bud stage.
Remarks  Effective on weeds in the Asteraceae (sunflower), Polygonaceae (knotweed), and legume families. Plants should be actively growing at time of treatment. Wet foliage at time of treatment may decrease control.
Caution  Do not contaminate irrigation ditches or water for irrigation or domestic use. Do not allow spray draft to contact potatoes, beans, or certain other crops.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  clopyralid + 2,4-D (Curtail)
Rate  2 to 4 quarts/A Curtail
Time  Apply after most knapweed rosettes have emerged but before flower stem elongates. Apply to Canada thistle before bud stage.
Remarks  Effective on diffuse and spotted knapweed and Canada thistle. Also controls many other weeds in the composite and legume families.
Caution  Do not contaminate irrigation ditches or water for irrigation or domestic use. Do not allow spray drift to contact potatoes, beans, or certain other crops.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (clopyralid) pyridine; (2,4-D) phenoxy acetic acid
•  dicamba (Banvel, Trooper, Vanquish, Rifle,or Clarity)
Rate  0.25 to 2 lb ai/A
Time  Apply to actively growing vegetation.
Remarks  Controls many annual and perennial broadleaf weed species as well as brush. Other herbicides often are combined and sold under a variety of trade names. Consult label for rates, times of application, use restrictions, and preparations for each of these proprietary mixtures.
Caution  Do not use in areas where roots of desirable vegetation may extend.
Site of action  Group 4: synthetic auxin
Chemical family  Benzoic acid
•  diflufenzopyr + dicamba (Overdrive)
Rate  0.175 to 0.35 lb ae/A (4 to 8 oz/A)
Time  Apply to actively growing broadleaf weeds.
Remarks  Controls many annual, biennial, and perennial broadleaf weeds and vine species, including biennial thistle, Canada thistle,  kochia, and marestail (horseweed). Rate depends on weed species and growth stage at time of treatment. For improved uptake, use a nonionic surfactant or a methylated seed oil on hard-to-control perennials and waxy-leaf species or when weeds are under moisture or temperature stress.
Caution  Do not plant any crop within 30 days of application. Do not exceed 10 oz/A of Overdrive per season.
Site of action  (diflufenzopyr) Group 19: inhibits indole acetic acid transport; (dicamba) Group 4: synthetic auxin
Chemical family  (diflufenzopyr) semicarbazone; (dicamba) benzoic acid
•  flumioxazin (Payload)
Rate  0.25 to 0.38 lb ai/A (8 to 12 oz/A)
Time  Preemergence, to bare soil, or postemergence.
Remarks  Broadleaf weed control but weak on most grasses. Do not exceed 0.38 lb ai/A per application or 0.75 lb ai/A per year. Moisture is required to activate preemergence applications. Adding an adjuvant enhances postemergence applications; good spray coverage is required.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  N-phenylphthalimide
•  fluroxypyr (Vista)
Rate  0.125 to 0.5 lb ae/A
Time  Apply when weeds are small and/or actively growing.
Remarks  Apply in spray volume of 3 gal/A or more by air or 5 gal/A or more by ground. Do not exceed 40 gal/A total spray volume. Spot treatments may be applied with a calibrated boom or hand sprayer. Only weeds emerged at treatment are controlled. Control may decrease if foliage is wet at time of application. Grasses are tolerant of fluroxypyr, but larger kochia is effectively controlled.
Caution  Do not apply when weather conditions favor drift from treated areas. Do not exceed 0.5 lb ae/A (2.67 pints/A) per year.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  isoxaben (Gallery)
Rate  0.5 to 1 lb ai/A
Time  Apply before germination.
Remarks  Area should be free of established weeds before application.
Site of action  Group 21: inhibits cell wall synthesis Site B
Chemical family  Benzamide
•  MCPA (several products)
Rate  3 lb ai/A
Time  Spray to wet weeds thoroughly when in bud to early bloom and again on fall regrowth.
Remarks  Controls Canada thistle, whitetop, and meadow buttercup.
Caution  Do not cut forage or graze livestock on treated areas within 7 days of treatment.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  metsulfuron (Escort)
Rate  0.3 to 1.8 oz ai/A (0.5 to 3 oz/A)
Time  For best results, apply postemergence to young, actively growing weeds or brush. Selective to many grasses. May combine with other products to broaden weed-control spectrum.
Remarks  For postemergence applications, include a nonionic or silicone surfactant at 0.25% by volume. Good coverage is essential for control.
Caution  Agitation required. Do not let spray drift to crops or other valuable plants or trees.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  picloram (Tordon)
Rate  0.125 to 1 lb ae/A
Time  Apply to foliage of actively growing weeds and brush.
Remarks  Picloram has soil-residual activity. It is formulated in several mixtures including combinations with 2,4-D.
Caution  Most formulations are restricted. Follow all use restrictions and precautions on label.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  quinclorac (Paramount)
Rate  4 to 6 oz ai/A (5.3 to 8 oz/A)
Time  Apply to actively growing weeds.
Remarks  Timing and rate of application depends on target weeds. Has activity on field bindweed, leafy spurge, sowthistle, Canada thistle,and clovers. Must add methylated seed oil at 1 to 2 pints/A or crop oil concentrate at 2 pints/A. Plant uptake is through both the foliage and roots. Rain after application is important for soil uptake.
Caution  Do not exceed 12 oz ai/A per calendar year. Do not allow to drift to sensitive crops. Do not apply to water or to irrigation ditches or areas that channel water entering cropland.
Site of action  Group 4: synthetic auxin
Chemical family  Quinoline carboxylic acid
•  triclopyr (Garlon)
Rate  1 to 8 lb ae/A
Time  Apply when woody plants and weeds are actively growing. The ester formulation may be used in the dormant season. See label for instructions.
Remarks  Controls certain perennial broadleaf weeds and woody plants. Rates depend on weed species, stage of maturity, and environmental conditions. If using lower rates on hard-to-control species, they may resprout a year later.
Caution  See label for grazing restrictions.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  triclopyr + 2,4-D (Crossbow)
Rate  1 quart to 4 gal/A, depending on weed species
Time  Apply during warm weather when brush and weeds are actively growing.
Remarks  Controls most species of unwanted woody plants as well as annual and perennial broadleaf weeds.
Caution  Application under drought conditions may provide less than desirable results. Use low spray pressures to minimize spray drift. Avoid contacting nearby susceptible crops or other desirable plants. Avoid contaminating water for irrigation or domestic use. Do not use or store near heat or open flame.
Site of action  (both) 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, depending on species and on target weed size and growth stage
Time  Apply when broadleaf weeds are actively growing.
Remarks  Controls many herbaceous broadleaf weeds. Add nonionic surfactant at surfactant manufacturer’s recommended rate. Apply in at least 10 gal/A water by ground. The smaller the annual weeds, the easier they are to control. Spray biennial species in the seedling to rosette stage, before flower stalks are apparent.
Caution  Do not exceed 4 pints/A per year. Do not allow drift to desirable vegetation. Avoid application under completely calm conditions which may be conducive to air inversions. Do not apply to newly seeded areas until grass is well established. Injures or kills forbs and other broadleaf  vegetation. Note label restrictions on overseeding or reseeding.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (both) pyridine
•  2,4-D (several products)
Rate  1 to 4 lb ae/A
Time  Apply when annual weeds are young and growing vigorously. Apply when perennial weeds are growing rapidly—generally, near the bud stage. Repeated applications may be necessary.
Remarks  Controls many annual, biennial, and perennial broadleaf weeds.
Caution  Do not apply when conditions favors drift from treated areas. Do not contaminate water for irrigation or domestic use.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid

NONCROPLAND AND RIGHT-OF-WAY—Brush Control
•  dicamba (Banvel, Trooper, Rifle, or Clarity)
Rate  0.25 to 2 lb ai/A
Time  Apply to actively growing vegetation.
Remarks  Controls many annual and perennial broadleaf weed species as well as brush. Other herbicides often are combined and sold under a variety of trade names. Consult label for rates, times of application, use restrictions, and preparations for each of these proprietary mixtures.
Caution  Do not use in areas where roots of desirable vegetation may extend.
Site of action  Group 4: synthetic auxin
Chemical family  Benzoic acid
•  fosamine (Krenite S)
Rate  6 to 24 lb ai/A
Time  Apply in late summer or early fall before fall coloration.
Remarks  Apply as a foliar spray to brush. Can be used in either air or ground equipment. Susceptible treated plants fail to refoliate the following spring. Total spray coverage is required.
Site of action  Not well understood
Chemical family  Organophosphorus
•  glyphosate
Rate  1.5 to 3.75 lb ae/A, depending on target species
Time  Apply to foliage of actively growing woody plants.
Remarks  Results are best if applied in late summer or fall after fruit forms. In arid areas, results are best if applied in spring to early summer when brush species have a high moisture content.
Caution  Control may be reduced if applied to stressed plants or after a fall frost.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  imazapyr (Arsenal, Arsenal Applicator Concentrate, or Chopper)
Rate  0.25 to 1.5 lb ai/A
Time  Apply postemergence to weeds or brush.
Remarks  Controls most annual and perennial grasses, broadleaf weeds, vines, brambles, and woody brush and tree species for forest management site preparation and release.
Caution  Do not apply where chemical may contact roots of desirable trees or other plants.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  metsulfuron (Escort)
Rate  0.6 to 1.2 oz ai/100 gal (1 to 2 oz/A)
Time  Apply to brush when brush is fully leafed out until the beginning of fall leaf color.
Remarks  Rate depends on species to be controlled. Adding a nonionic surfactant enhances activity. Complete coverage of all leaves and stems is required.
Caution  Do not allow spray to drift to adjacent crops or other valuable plants or trees.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  picloram (Tordon)
Rate  0.125 to 1 lb ae/A
Time  Apply to foliage of actively growing weeds and brush.
Remarks  Picloram has soil residual activity. It is formulated in several mixtures, including combinations with 2,4-D.
Caution  Most formulations are restricted. Follow all use restrictions and precautions on label.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  tebuthiuron (Spike)
Rate  1 to 4 lb ai/A
Time  East of Cascades, apply in fall; west of Cascades, apply in spring.
Remarks  Rate depends on species to be controlled. Requires rain to move into soil.
Caution  Kills desirable trees, shrubs, and other vegetation with roots in the treated area.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  triclopyr (Garlon)
Rate  1 to 8 lb ae/A, depending on weed species, maturity stage, and environmental conditions
Time  Apply when woody plants and weeds are actively growing. The ester formulation may be used in the dormant season. See label for instructions.
Remarks  Controls certain perennial broadleaf weeds and woody plants. If lower rates are used on hard-to-control species, they may resprout a year later.
Caution  See label for grazing restrictions.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  triclopyr + 2,4-D (Crossbow)
Rate  1 quart to 4 gal/A
Time  Apply during warm weather when brush and weeds are actively growing.
Remarks  Controls most species of unwanted woody plants as well as annual and perennial broadleaf weeds. Rates depend on weed species.
Caution  Application during drought may have less-than-desired results. Use low spray pressure to minimize spray drift. Avoid contacting nearby susceptible crops or other desirable plants. Avoid contaminating water for irrigation or domestic use. Do not use or store near heat or open flame.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (triclopyr) pyridine; (2,4-D) phenoxy acetic acid
•  2,4-D LV ester (several products)
Rate  1.9 to 7.6 lb ae/A, depending on target species.
Time  Apply when woody plants are in full leaf and actively growing.
Remarks  Use higher rates if plants are stressed. Adding oil or wetting agents and/or using high carrier volumes may enhance control.
Caution  Applications to stressed plants may reduce control. Do not let spray drift off target.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
NONCROPLAND AND RIGHT-OF-WAY—Under Asphalt
•  dichlobenil (Casoron or Barrier)
Rate  10 to 12 lb ai/A
Time  Apply after final grade is established.
Remarks  Do not move soils after applying. Pave as soon as possible after applying. Forms a vapor barrier, preventing roots and shoots from penetrating. Reportedly safe to use near desirable vegetation. For resurfacing work, control existing weeds before applying dichlobenil.
Caution  Herbicide will volatilize and be lost if not immediately covered by asphalt.
Site of action  Group 20: inhibits cell wall synthesis Site A.
Chemical family  Nitrile
•  trifluralin (Treflan)
Rate  12 to 16 lb ai/A
Time  Apply after final grade is established or after additions of base rock.
Remarks  Remove rhizomes, tubers, stolons, or other vegetative plant parts by scalping with a grader blade deep enough to ensure their complete removal before application. After applying, do not move soils, and pave as soon as possible. Forms a vapor barrier, preventing roots and shoots from penetrating. Safe to use near desirable vegetation.
Caution  Herbicide is volatile and will be lost if not immediately covered by paving. Do not apply to areas where asphalt will be laid directly on soil.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  pendimethalin (Pendulum 3.3EC)
Rate  2 to 4 lb ai/A (2.4 to 4.8 quarts/A)
Time  Apply after final grade is established.
Remarks  Remove rhizomes, tubers, and other vegetative plant parts by scalping with a grader blade before application.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  prometon (Pramitol 25E)
Rate  7.5 to 10 gal/A
Time  Apply after final grade is established.
Remarks  Remove rhizomes, tubers, and other vegetative plant parts by scalping with a grader blade before application. Apply in at least 100 gal/A water. Pave as soon as possible after applying.
Caution  Do not allow treated soil to wash or move into untreated area. Do not apply under asphalt coatings less than 2 inches thick. Desirable plants may be killed or injured if herbicide is applied where roots are or may extend.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazine
•  imazapic (Plateau, Imazapic E 2SL) 
Rate  0.1875 lb ai/A (12 oz/A product)
Time  Apply to soil surface after final grade is established.
Remarks  Incorporation improves control if soil is not moist at treatment. Either incorporate 2 inches into soil, using a rototiller or disc, or with 1 inch of rain or irrigation.
Caution  Do not let treated soil wash or move into untreated area. Desirable plants may be injured if their roots extend into treated areas or if planted in treated areas.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  imazapyr (Arsenal)
Rate  1.5 lb ae/A
Time  Apply after final grade is established.
Remarks  Before applying, use a grader blade to scalp and remove rhizomes, tubers, and other vegetative plant parts. Apply in at least 100 gal/A water. Pave as soon as possible after application. If soil is not moist at application, use a rototiller or disc to incorporate 4 to 6 inches deep. Rain or 1 inch of irrigation also provides uniform incorporation. Use only in industrial sites or where the pavement has a suitable barrier along the perimeter to prevent root encroachment of desirable plants.
Caution  Do not let treated soil wash or move into untreated areas. Desirable plants may be killed or injured if herbicide is applied where roots are or may extend. See label for areas where this product can be used.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  imazapyr + diuron (Sahara)
Rate  10 lb/A
Time  Apply immediately before paving to avoid lateral movement of the herbicide as a result of soil movement due to rain or mechanical activity.
Remarks Before applying, use a grader blade to scalp and remove rhizomes, tubers, and other vegetative plant parts. If soil is not moist at application, incorporate herbicide mechanically. Use only in industrial sites or where pavement has a suitable barrier along the perimeter to prevent root encroachment of desirable plants.
Caution  Do not use under pavement in residential or recreational areas. Desirable plants may be injured if their roots extend into treated areas or if planted in treated areas.
Site of action  (imazapyr) Group 2: acetolactate synthase (ALS) inhibitor; (diuron) Group 7: photosystem II inhibitor
Chemical family  (imazapyr) imidazolinone; (diuron) substituted urea
•  sodium chlorate + sodium  metaborate tetrahydrate (Monobor-chlorate)
Rate  0.9 lb of Monobor-chlorate per 100 sq ft
Time  After subgrade is finished and before asphalt paving.
Remarks  Do not apply where tree roots extend into treated area. Do not let runoff water wash the herbicide away from treated area. Granules may be dissolved in water and sprayed on or may be applied dry and followed with at least 2 gal water/100 sq ft. Reentry interval is 12 hr.
Site of action  None generally accepted
Chemical family  Inorganic
•  sulfometuron (Oust)
Rate  3 to 6 oz ai/A (4 to 8 oz/A)
Time  Apply just before the asphalt or concrete coating to avoid possible lateral movement of the herbicide by rain or mechanical activity.
Remarks  Use on parking lots, highway shoulders, median strips, roadways, and other industrial sites. Remove rhizomes, tubers, or other vegetative parts in the site. Will not control woody vegetation such as small trees, brush, or woody vines; their roots must be removed from the site before application.
Caution  Do not use under pavement in residential areas such as driveways, or in recreational areas, jogging or bike paths, tennis courts, or golf cart paths. Avoid drift of spray into planters or ornamental bedding areas or near the treated area, as injury may result. Desirable plants may be injured if their roots extend into treated area.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  bromacil (Hyvar X)
Rate  4.8 to 12 lb ai/A
Time  Apply immediately before paving to avoid lateral movement of the herbicide as a result of soil movement due to rain or mechanical activity.
Remarks  Remove rhizomes, tubers, and other vegetative plant parts by scalping with a grader blade before application.
Caution  Do not use under pavement in residential or recreational areas. Desirable plants may be injured if their roots extend into treated areas or if planted in treated areas.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Uracil
•  bromacil + diuron (Krovar IDF)
Rate  17 to 31 lb/A
Time  Apply immediately before paving to avoid lateral movement of the herbicide as a result of soil movement due to rain or mechanical activity.
Remarks  Before applying, use a grader blade to scalp and remove rhizomes, tubers, and other vegetative plant parts. 
Caution  Do not use under pavement in residential or recreational areas. Desirable plants may be injured if their roots extend into treated areas or if planted in treated areas.
Site of action  (bromacil) Group 5: photosystem II inhibitor; (diuron) Group 7: photosystem II inhibitor
Chemical family  (bromacil) uracil; (diuron) substituted urea
•  sulfometuron + chlorsulfuron (Landmark MP, Landmark XP, or Landmark II MP)
Rate  Consult label; each formulation has a different use rate
Time  Apply immediately before paving to avoid lateral movement of the herbicide as a result of soil movement due to rain or mechanical activity.
Remarks  Before applying, use a grader blade to scalp and remove rhizomes, tubers, and other vegetative plant parts. 
Caution  Do not use under pavement in residential or recreational areas. Desirable plants may be injured if their roots extend into treated areas or if planted in treated areas.
Site of action  (both) Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  (both) sulfonylurea
•  tebuthiuron (Spike 80DF)
Rate  1.6 to 4 lb ai/A
Time  Apply immediately before paving to avoid lateral movement of the herbicide as a result of soil movement due to rain or mechanical activity.
Remarks  Before applying, use a grader blade to scalp and remove rhizomes, tubers, and other vegetative plant parts.
Caution  Do not use under pavement in residential or recreational areas. Desirable plants may be injured if their roots extend into treated areas or if planted in treated areas.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea