Grass and Broadleaf Weeds

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).

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, because they like its salty taste. Do not allow livestock to 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 the Cascades, in March or early April west of the 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 re-treatment 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

chlorsulfuron + sulfometuron + sulfentrazone (Throttle XP)

Rate 12.5 oz/a

Time Apply preemergence or early postemergence to weeds.

Remarks Not recommended for paved areas but for farmyards, fuel storage areas, fence rows and industrial sites.

Caution Do not apply to powdery, dry soil or sandy soil if there is little likelihood of rainfall soon after treatment because of dust particles that move the herbicide to sensitive plants. Do not tank mix with HYVAR X-L.

Site of action (chlorsulfuron, sulfometuron) Group 2: acetolactate synthase (ALS) inhibitor, (sulfentrazone) Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Sulfonylurea, Triazinone

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 by applying irrigation water.

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

dithiopyr (Dimension 2EW)

Rate 2 pints product/a

Time Apply preemergence to weeds, affects some grass and broadleaf species.

Remarks Activated by 1/2 inch or more of rainfall. Litter can reduce effectiveness. Forage cannot be used by livestock. Can be applied at 3 to 4 month intervals to extend preemergent control, but no more than 6 pints product/a per year should be applied.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Pyridine

diuron (Karmex DF)

Rate 4 to 12 lb ai/a

Time Apply in fall or late winter east of the Cascades and in spring west of the Cascades.

Remarks Use higher rates for perennial weed control, lower rates for annual weed control. Make maintenance applications on areas previously treated by applying 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 glyphosate 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 hours of 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 104 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 hours 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, Panoramic)

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. Effective on downy brome, African wiregrass, and medusahead wildrye. Effectiveness may be poor if dense litter is present.

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

Chemical family Imidazolinone

imazapyr (Arsenal, 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

indaziflam (Esplanade 200 SC)

Rate 3.5 to 7 oz/a

Time Apply preemergence to weeds.

Remarks Controls many annual grasses and broadleaf weeds.

Caution Do not apply more than 10 oz/a per year. Keep away from surface water, at least 25 feet, and areas below the mean watermark.

Site of action Group 29: cellulose biosynthesis inhibitor

Chemical family Alkylazine

isoxaben + trifluralin (Snapshot2.5TG)

Rate Consult labels.

Time Apply before weeds germinate.

Remarks Controls annual grass and broadleaf weeds. Areas treated should be free from 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 air temperatures exceed 70°F and before weeds are more than 8 inches high. Best results are with rain or irrigation within 2 weeks of application. See label about soil types.

Caution Do not enter treated area for 24 hours after applying unless wearing protective clothing.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

norflurazon (Solicam DF)

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)

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 re-treatments are necessary. Use 0.25% of a nonionic adjuvant to enhance weed control.

Caution Not registered for use in Oregon. 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 SL 2.0)

Rate 1.5 to 3 pints/a

Time Apply when weeds are young and succulent.

Remarks Paraquat is a contact herbicide that kills only the tops of most perennial weeds. Re-treatments are necessary. Add a nonionic surfactant or crop oil concentrate as directed on the label to spray. Use enough water (usually at least 20 gal/a) 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 3.3 EC, Prowl H2O)

Rate 2 to 4 lb ai/a (2.4 to 4.8 quarts/a product)

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 or incorporated 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

penoxsulam + oxyfluorfen (Cleantraxx)

Rate 3 to 4.5 pints/a

Time Apply prior to emergence of weeds.

Remarks Apply for pre- and postemergent control of weeds. High rate for preemergent application will increase duration of control. Grass and broadleaf weeds are controlled, see label for weeds that require more than 3 pints/a. Requires 0.5 inches of precipitation to activate within 21 days of application.. Apply in 10 to 30 gallons of spray per acre.

Caution Do not apply more than 4.5 pints/a in a crop season. Keep application at least 25 feet from any water body.

Site of action Group 2, 14: acetolactate synthase (ALS) inhibitor, protoporphyrinogen oxidase inhibitor

Chemical family Triazolopyrimidine, Diphenylether

prometon (Pramitol)

Rate 10 to 15 lb ai/a

Time Apply at weed emergence or within 2 to 3 months after spring growth begins.

Remarks Prometon has 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

rimsulfuron (Matrix, Laramie)

Rate 2 to 4 oz /a

Time Apply before or soon after weeds emerge.

Remarks Controls many annual grasses, and some annual broadleaf species. Add a nonionic surfactant at 1 quart/100 gal spray to improve activity.

Caution Consult label if there are plans to seed grasses after application.

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

Chemical family Sulfonylurea

sulfometuron (Oust)

Rate 1 to 6 oz ai/a (1.33 to 8 oz/a product)

Time Apply before or soon after weeds emerge for nonselective control. Rain required to fully activate herbicide.

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 when soils are water-saturated. Do not treat powdery, dry soils and light, sandy soils unless rain is likely after treatment. Do not let spray drift to adjacent crops.

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

Chemical family Sulfonylurea