Chemical Fallow East of the Cascades

Sandy Macnab
Revised: 
March 2016

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 by weight (or liquid equivalent) may improve performance on annual weeds.

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)

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

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, crop oil concentrate, or methylated seed oil is required. Add 0.25% (v/v) nonionic surfactant or 1.5 to 2% (v/v) of a crop oil concentrate or methylated seed oil. After applying Aim, 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.

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

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family triazolinone

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

Rate 0.095 to 0.126 lb ae/A clopyralid + 0.50 to 0.67 lb ae/A 2,4-D (2 to 2.66 pints/A Curtail)

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 may be based on rainfall and soil types. Compatible with most non-pressurized liquid fertilizers, however, compatibility test recommended before mixing.

Caution A restricted use herbicide. Wear protective clothing when spraying and handling. Avoid contact, especially with eyes. Seven day pre-harvest for forage cut for hay. Plant only labeled crops within 29 days following application. Re-entry interval for workers is 48 hours.

Site of action Group 4 synthetic auxin

Chemical family pyridine carboxylic acid

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

Rate 0.25 to 0.5 lb ae/A dicamba + 0.19 to 0.375 lb ae/A glyphosate

Time Apply on fallow land that will be planted to wheat.

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.

Caution A 45-day waiting period is required between a Banvel or 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) none generally accepted

diflufenzopyr + dicamba (Distinct)

Rate 0.25 to 0.5 lb ae/A diflufenzopyr + 0.063 to 0.125 lb ae/A dicamba (2.0 to 4.0 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. A reduced rate of Distinct (2 to 4 oz/A) can be combined with glyphosate or another herbicide effective on the target weed species. Control of annual and perennial grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat.

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. Do not graze or harvest hay from treated areas.

Site of action Group 19: Inhibits indole acetic acid transport; Group 4: synthetic auxin

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

flumioxazin (Valor SX)

Rate 0.064 to 0.128 lb ai/A (2 to 4 oz/A Valor SX)

Time Apply in the fall or early spring in combination with a burndown herbicide such as glyphosate to control emerged weeds. Weed species controlled by residual activity are listed on the label.

Remarks Consult label for restrictions on planting rotational crops following Valor application in fallow. Do not apply to frozen or snow covered soil.

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

glufosinate ammonium (Rely 280)

Rate 0.40 to 0.53 lb ai/A (22 to 29 fl oz/A plus ammonium sulfate)

Time Apply on land to be fallowed before seeding crops. Control is best on weeds 2 to 4 inches tall.

Remarks Small grains can be planted 70 days after Rely 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 by weight is required.

Site of action Group 10: inhibits glutamine synthetase.

Chemical family Phosphinic acid.

glyphosate (several products)

Rate 0.28 to 0.38 lb ae/A + 0.5% nonionic surfactant, or 0.47 to 0.56 lb ae/A for grass in boot stage or for broadleaf weeds that have bolted.

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 by weight (or liquid equivalent) may improve performance on annual weeds.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

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 Can be used up to 0.75 lb ai/A 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. Tillage maintains weed control in summer. May apply with paraquat or glyphosate (see label).

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 (various product names)

Rate 0.5 to 1 lb ae/A paraquat (2 to 4 pints/A Gramoxone Inteon, 1.3 to 2.6 pints/A Firestorm)

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, crop oil concentrate, or methylated seed oil with the application.

Caution A restricted-use herbicide. Wear protective clothing when spraying and handling. Avoid contact, especially with eyes. Do not graze treated fields. Dry, dusty conditions will decrease activity. Do not apply if wheat has emerged.

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 or nonionic surfactant 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. Control of annual and perennial grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat.

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 0.20 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 or ammonium sulfate may improve weed control under stress conditions. Good spray coverage is essential. Control of annual and perennial grasses requires a tank-mix with a burndown herbicide such as glyphosate, glufosinate, or paraquat.

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 6 and 27: Photosystem II inhibitor + 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)

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 plus ammonium sulfate or urea ammonium nitrate is required for burndown activity. See label for more information on adjuvants and tank-mixes.

Caution Do not exceed 6 fl oz/A per year. Sharpen may cause transitory injury to cool-season grasses under certain conditions. 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 Use rate depends on soil texture and percent soil organic matter. Refer to label for rate information. For control of emerged weeds a nonionic surfactant, crop oil concentrate, methylated seed oil, or equivalent adjuvant is required as specified on the label. Optimum broad-spectrum grass and broadleaf weed 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, this product requires shallow incorporation.

Caution Do not apply to frozen soils or existing snow cover. Do not apply to soils classified as sand with 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 in spray mixture at 1 to 2 pints/A. Do not apply through irrigation systems. Do not apply if rain is expected within 4 hours. Apply only once per year. Do not exceed 5 oz/A per year. Optimum broad-spectrum grass and broadleaf weed control requires a tank-mix with a burndown herbicide such as glyphosate.

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.

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

Chemical family (triasulfuron) sulfonylurea; (dicamba) benzoic acid