Chemical Fallow East of the Cascades

Judit Barroso
Revised: 
March 2022

2,4-D (several products) + glyphosate (several products)

Rate 0.16 to 0.32 lb ae/A 2,4-D + 0.19 to 0.38 lb ae/A glyphosate. Use the higher rate in no-till, or when plants are beyond seedling stage.

Time Apply in 3 to 10 gal/A water by ground or 3 to 5 gal/A by air. Apply on land to be fallowed before seeding crops, or before crop emerges, but before weeds are taller than 6 inches. Spray bindweed when runners are at least 10 inches long.

Remarks Use the higher rate to improve control of coast fiddleneck, corn gromwell, purple mustard, and other winter annuals. Adding 2% dry ammonium sulfate (AMS) by weight (or liquid equivalent) may improve performance on annual weeds. REI 12 hr for the low volatile ester (LVE) formulation and 48 hr for the amine formulation.

Caution Do not apply on frost-damaged or severely stressed weeds. Apply to green, vigorous seedlings and volunteer cereals.

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

carfentrazone (Aim EC, and other trade names)

Rate 0.008 to 0.031 lb ai/A (0.5 to 2 fl oz/A Aim EC)

Time Apply to actively growing weeds up to 4 inches tall, and to rosettes less than 3 inches across.

Remarks Adjust rate for weed species and density of weed stand. Optimum broad-spectrum control of annual and perennial weeds and grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat. The use of a nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil (MSO) is required. Add 0.25% (v/v) NIS or 1.5 to 2% (v/v) of a COC or MSO. After applying Aim EC, registered crops may be planted any time, subject to specific crop restrictions that may be found on the label. All other crops may be planted 12 months after application. Good spray coverage is essential. REI 12 hr.

Caution Do not exceed 0.031 lb ai/A Aim EC per season.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Triazolinone

clethodim (Shadow, SelectMax, and other trade names)

Rate 0.045 to 0.120 lb ai/A (6 to 16 fl oz/A Shadow that has 12.6% ai), 0.068 to 0.120 lb ai/A (9 to 16 fl oz/A SelectMax that has 26.4% ai). Rates will vary depending on product concentration. Consult the label for rate accuracy.

Time After grasses emerge. See label for details.

Remarks Controls annual and perennial grasses. Rate is dependent upon annual vs perennial grass weeds present. Use higher rates to control perennial weeds. Add nonionic surfactant at 0.25% v/v or COC or MSO at 1% v/v, ammonium sulfate can also be used at 2.5 to 4 lb/A. The minimum interval between clethodim applications is 14 days. Do not apply more than 64 fl oz/A per year. REI is 24 hr.

Caution Does not control rattail fescue.

Site of action Group 1: acetyl CoA Carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione

clopyralid + 2,4-D (Curtail, Commando)

Rate 0.095 to 0.19 lb ae/A clopyralid + 0.50 to 1.0 lb ae/A 2,4-D (2 to 4 pints/A Curtail or Commando)

Time Apply to actively growing, young weeds, either post-harvest or in the spring/fallow.

Remarks Extreme growing conditions (i.e., drought or near freezing temperatures) prior to, at, or following application may reduce weed control. Days to plant back varies from 30 days (wheat barley, field corn, oats, grasses) to 5 months (canola, rapeseed, flax sugar beets), and from 10.5 months to 18 months for other crops. Plantback restrictions are based on rainfall and soil types. Compatible with most non-pressurized liquid fertilizers, however, a compatibility test is recommended before mixing. Restricted entry interval (REI) for workers is 48 hours.

Caution Wear protective clothing when spraying and handling. Avoid contact, especially with eyes. Plant only labeled crops within 29 days following application.

Site of action (both) Group 4: synthetic auxin

Chemical family Pyridine carboxylic acid

dicamba (Clarity and others) + glyphosate (several products)

Rate 0.125 to 1 lb ae/A dicamba (4 to 32 oz/A Clarity) + 0.19 to 0.375 lb ae/A glyphosate

Time For best performance, apply when weeds are in 2-leaf or 3-leaf stage and rosettes are less than 2 inches across.

Remarks Use lower rates on actively growing weeds less than 4 inches tall. Use higher rates when weeds are drought-stressed or 4 to 6 inches tall. Control of annual and perennial grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat. No rotational cropping restrictions apply at 120 days or more following application. REI 24 hr.

Caution A 45-day waiting period is required between a Clarity application and planting wheat. Do not graze for 8 weeks after application.

Site of action (dicamba) Group 4: synthetic auxin; (glyphosate) Group 9: inhibits EPSP synthase.

Chemical family (dicamba) Benzoic acid; (glyphosate) Glycine

diflufenzopyr + dicamba (Distinct)

Rate 0.025 to 0.1 lb ae/A diflufenzopyr + 0.063 to 0.1 lb ae/A dicamba (2.0 to 8.0 oz/A Distinct)

Time Apply when weeds are small and actively growing.

Remarks Thorough spray coverage of weeds is necessary. Make applications with an adjuvant as directed on the Distinct label. Avoid disturbing (e.g. with tillage) for at least 7 days following application to allow best weed control. REI 24 hr.

Caution Do not plant any crops within 120 days after last application of Distinct with some exceptions as specified on the Distinct label. Do not apply through any type of irrigation system.

Site of action (diflufenzopyr) Group 19: Inhibits indole acetic acid transport; (dicamba) Group 4: synthetic auxin

Chemical family (diflufenzopyr) Semicarbazone; (dicamba) Benzoic acid

flumioxazin (Valor EZ and other trade names)

Rate 0.032 to 0.128 lb ai/A (1 to 4 oz/A Valor EZ)

Time Apply in the fall or early spring in combination with a burndown herbicide such as glyphosate to control emerged weeds.

Remarks Weed species controlled by residual activity are listed on the label. Consult label for restrictions on planting rotational crops following Valor EZ application in fallow. Do not apply to frozen or snow covered soil. REI 12 hr.

Caution Do not perform any tillage operation after application or residual weed control will be reduced. Allow at least 4 months after application to plant wheat. Longer plant-back restrictions may apply.

Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor

Chemical family N-phenylphthalimide

flumioxazin + pyroxasulfone (Fierce, Fierce EZ and other trade names)

Rate 0.0628 to 0.094 lb ai/A flumioxazin + 0.080 to 0.119 lb ai/A pyroxasulfone (6 to 9 oz/A Fierce EZ). Rates will vary depending on the active ingredient concentration in the different products. Consult label for accurate rates.

Time Fall application to provide residual weed control in fields that will be planted the following spring. Refer to label for crop rotation interval and weed controlled or suppressed.

Remarks If weeds have emerged at time of application, use Fierce in combination with a labeled burndown herbicide and recommended adjuvants. Abnormally warm or wet winters will reduce the length of weed control observed in the spring. REI 12 hr.

Caution See Fierce label for crop rotation restrictions.

Site of Action (flumioxazin) Group 14: protoporphyrinogen oxidase (PPO) inhibitor; (pyroxasulfone) Group 15: inhibits very long chain fatty acid synthesis.

Chemical family (flumioxazin) N-phenylphthalimide; (pyroxasulfone) Pyrazole

glufosinate ammonium (Rely 280 SL and other trade names)

Rate 0.40 to 0.53 lb ai/A (22 to 29 fl oz/A Rely 280 SL)

Time Control is best on weeds 2 to 4 inches tall.

Remarks Small grains can be planted 70 days after Rely 280 SL application. See label for further crop rotation restrictions. Apply in a minimum of 15 gal/A water by ground application and 10 gal/A by aerial application. To improve total weed control, a tank-mix with 2,4-D, dicamba, or other labeled broadleaf herbicide product is recommended. Adding 2% dry ammonium sulfate (AMS) by weight is required. REI 12 hr.

Site of action Group 10: inhibits glutamine synthetase

Chemical family Phosphinic acid

glyphosate (several products)

Rate 0.375 to 2 lb ai/A (12 to 64 fl oz/A GlyStar Original that has 41% of ai) or 0.281 to 1.55 lb ai/A (8 to 44 fl oz/A Roundup PowerMAX that has 48.7% of ai). Rates will vary depending on product concentration.

Time Apply on land to be fallowed before seeding crops or apply before crop emerges. Control is best on weeds 2 to 4 inches tall. Use low rates on weeds less than 4 inches tall and not moisture-stressed.

Remarks Apply in 3 to 5 gal/A water by air or 5 to 10 gal/A water by ground. To improve control of kochia, lambsquarters, prickly lettuce, pigweed, and Russian thistle, add a 2,4-D, dicamba, or other labeled broadleaf herbicide product. Use lower rate on downy brome, foxtails, mustards, and volunteer wheat. Some glyphosate products may require additional surfactant as specified on the individual product label. Adding 2% dry ammonium sulfate (AMS) by weight (or liquid equivalent) may improve performance on annual weeds. REI 4 hr.

Site of action Group 9: inhibits EPSP synthase

Chemical family Glycine

metribuzin (several products)

Rate 0.38 to 0.62 lb ai/A (12.2 to 19.8 oz/A Tricor 4F, 8.1 to 13.2 oz/A Metribuzin 75)

Time Results are best if applied before weeds emerge or during early stages of weed growth (less than 2 inches tall or across).

Remarks Rates up to 0.75 lb ai/A allowed if applied in the fall. Treat fields after small grains have been harvested in a wheat–fallow rotation. Moisture (0.5 inch or more) is needed to activate herbicide. Fall treatment controls weeds through winter until late spring. May apply with paraquat, glyphosate, and others (see label). REI 12 hr.

Caution Do not graze treated fields. Do not reseed to winter wheat within 10 months after a fall application or 4 months (120 days) after a spring application. Do not plant spring cereals following fall application for fallow. Do not apply more than once per fallow period.

Site of action Group 5: photosystem II inhibitor

Chemical family Triazinone

paraquat (Gramoxone SL 3.0 and other trade names)

Rate 0.671 to 1.395 lb ai/A paraquat (1.3 to 2.7 pints/A Gramoxone SL 3.0). Rates can vary depending on the product concentration. Consult label for accurate rates.

Time Apply to emerged weeds in fall or spring fallow land.

Remarks Results are best when a delay between tillage and planting allows weeds to emerge. Controls only annual weeds. Always use a nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil (MSO) with the application. REI 12 hr.

Caution A restricted-use herbicide. To be used by certified applicators only. Not to be used by uncertified persons working under the supervision of a certified applicator. May be fatal if swallowed or inhaled. See label for correct protective equipment. Applicators, mixers, and loaders must wear long-sleeve shirt and long pants, shoes plus socks, protective eyewear (applicator), face shield (mixers and loaders), Category A chemical resistant gloves, chemical resistant apron (mixers and loaders), and a dust mist NIOSH-approved respirator with an N, R, P, or HE filter. Avoid contact, especially with eyes. Do not graze treated fields. Dry, dusty conditions will decrease activity.

Site of action Group 22: photosystem I inhibitor

Chemical family Bipyridilium

pyraflufen ethyl (Vida)

Rate 0.0008 to 0.0033 lb ai/A (0.5 to 2 fl oz/A Vida)

Time Apply to actively growing weeds up to 4 inches tall, and to rosettes less than 3 inches across.

Remarks Adjust rate for weed species and density of weed stand. Adding a crop oil concentrate (COC) or nonionic surfactant (NIS) is recommended. After applying Vida, plant registered crops any time. Plant crops not listed on the label 30 days after application. Good spray coverage is essential. Use an approved agricultural buffering agent to pH 5.0 or less if using Vida in a water source of ≥ pH 5.0. Always buffer the water source BEFORE adding Vida herbicide to the spray tank. Control of annual and perennial grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat. REI 12 hr.

Caution Do not exceed three applications or 5.5 fl oz/A during the fallow period. Allow 30 days between applications. Do not allow livestock to graze in treated areas.

Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor

Chemical family Phenylpyrazole

pyrasulfotole + bromoxynil (Huskie)

Rate 0.026 to 0.036 lb ai/A pyrasulfotole + 0.15 to 0.21 lb ai/A bromoxynil (11 to 15 fl oz/A Huskie)

Time Apply to actively growing weeds at growth stages recommended on label.

Remarks Adjust rate for weed species and density of weed stand. Adding a nonionic surfactant (NIS) or ammonium sulfate (AMS) may improve weed control under stress conditions. Good spray coverage is essential. For broad-spectrum control of annual and perennial grasses, tank-mix Huskie with glyphosate or glufosinate. REI 24 hours.

Caution Follow crop rotation guidelines listed on label. Do not allow livestock to graze in treated areas with 25 days of application.

Site of action (bromoxynil) Group 6: Photosystem II inhibitor; (pyrasulfotole) Group 27: HPPD inhibitor

Chemical family (bromoxynil) Nitrile + (pyrasulfotole) Isoxazole

saflufenacil (Sharpen)

Rate 0.02 to 0.04 lb ai/A (1 to 2 fl oz/A Sharpen) + recommended adjuvants (see label)

Time Apply when weeds are small and actively growing.

Remarks Sharpen controls mainly broadleaf weeds. Control of annual and perennial grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat. A methylated seed oil (MSO) plus ammonium sulfate (AMS) or urea ammonium nitrate (UAN) is required for burndown activity. See label for more information on adjuvants and tank-mixes. REI 12 hr.

Caution Do not exceed 6 fl oz/A per year. Disease, extremely cold weather, drought, extensive frost heaving, low or high pH, salinity, and other environmental pressures may weaken grass stands and make the crop more susceptible to herbicidal injury.

Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor

Chemical family Pyrimidinedione

sulfentrazone + carfentrazone (Spartan Charge)

Rate 0.09 to 0.25 lb ai/A sulfentrazone + 0.01 to 0.03 lb ai/A carfentrazone (3.75 to 10.2 fl oz/A Spartan Charge)

Time Apply in fallow when weeds are small and actively growing. Sufficient precipitation must occur after application to insure herbicide activation.

Remarks Refer to label for rate information. For optimum control of emerged weeds, a nonionic surfactant (NIS), crop oil concentrate (COC), methylated seed oil (MSO), or equivalent adjuvant is required as specified on the label. Optimum broad-spectrum grass and broadleaf weed post-emergence control requires a tank-mix with a burndown herbicide such as glyphosate. Residual weed control requires adequate precipitation for herbicidal activation. Herbicide application rate and residual activity is dependent on several factors including precipitation after application, soil moisture at time of application, soil type, soil pH, and organic matter. Where irrigation is not available and rainfall has not provided adequate activation, a shallow incorporation (less than 2 inches) is recommended. REI 12 hr.

Caution Do not apply to frozen soils or existing snow cover. Do not use on course soils classified as sand which have less than 1% organic matter. Do not apply more than 10.2 fl oz/A per 12-month period. Follow label restrictions for crop rotational intervals.

Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor

Chemical family Triazinone

triasulfuron + dicamba (Rave)

Rate 0.11 to 0.22 lb ai/A triasulfuron + 0.07 to 0.14 lb ai/A dicamba (2 to 4 oz/A Rave)

Time Fall or spring. Fall applications must be made before weeds are exposed to extended freezing. Apply in 5 to 20 gal/A water by ground or 2 to 10 gal/A by air.

Remarks Include a nonionic surfactant (NIS) in spray mixture at 1 to 2 pints/100 gal. Do not apply through irrigation systems. Do not apply if rain is expected within 4 hr. Apply only once per year. REI 24 hr.

Caution Wait at least 8 months after application to plant durum wheat. Other winter and spring wheat varieties may be planted after 12 days. See label for other crop rotation restrictions. Do not exceed 5 oz/A per year.

Site of action (triasulfuron) Group 2: acetolactate synthase (ALS) inhibitor; (dicamba) Group 4: synthetic auxin

Chemical family (triasulfuron) Sulfonylurea; (dicamba) Benzoic acid