Chemical Fallow East of Cascades
Dan Ball
Revised November 26, 2008

CHEMICAL FALLOW EAST OF CASCADES
•  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 3 to 10 gal/A water by ground. To improve control of kochia, lambsquarters, prickly lettuce, pigweed, and Russian thistle, add 0.5 lb ae/A of 2,4-D amine or 0.25 lb ae/A dicamba. 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
•  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 is to be planted to wheat.
Remarks  Use lower rates on actively growing weeds less than 4 inches tall. Use high rates when weeds are drought stressed or 4 to 6 inches tall.
Caution  A 45-day waiting period is required between a Banvel or Clarity application and planting wheat. Do not graze for 8 wk 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
•  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  To improve control of coast fiddleneck, corn gromwell, purple mustard, and other winter annuals; use the higher rate. 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
•  metribuzin (several products)
Rate  0.38 to 0.62 lb ai/A
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) 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 mo after a fall application or 4 mo (120 days) after a spring application. Do not apply more than once per fallow period.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazinone
•  paraquat (Gramoxone Inteon)
Rate  0.5 to 1 lb ae/A paraquat (2 to 4 pints/A Gramoxone Inteon)
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 the activity. Do not apply if wheat has emerged already.
Site of action  Group 22: photosystem I inhibitor
Chemical family  Bipyridilium
•  carfentrazone (Aim EC)
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. 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. All other crops may be planted 12 mo 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  Triazinone
•  pyraflufen ethyl (ET) 
Rate  0.0008 to 0.0032 lb ai/A (0.5 to 2 fl oz/A ET)
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 ET, plant registered crops any time. Plant crops not listed on the label 30 days after application. Good spray coverage is essential.
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 inhibitor
Chemical family  Phenylpyrazole
 •  pyrasulfotole + bromoxynil (Huskie) 
Rate  11 to 15 fl oz/A)
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.
Caution  Follow crop rotation guidelines listed on label.  Do not allow livestock to graze in treated areas with 25 days of application, or harvest straw or grain within 60 days after application.
Site of action  6 and 27: Photosystem II inhibitor + HPPD Inhibitor
Chemical family  nitrile + isoxazole
•  triasulfuron + dicamba (Rave)
Rate  0.176 to 0.35 oz ai/A triasulfuron + 1.1 to 2.2 oz ai/A dicamba (2 to 4 oz/A Rave)
Time  Fall or spring. Fall applications must be 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/yr.
Caution  Wait at least 8 mo 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
•  pronamide (Kerb) 
grass weeds
Rate  0.25 to 0.5 lb ai/A (0.5 to 1 lb/A Kerb)
Time  Apply mid-October to mid-December before soil freezes.
Remarks  Controls downy brome (cheatgrass), volunteer wheat, volunteer barley, bulbous bluegrass, jointed goatgrass, and common rye. Kerb is a soil-active herbicide absorbed by weed roots. Moisture is required to move Kerb into the weed root zone. Broadleaf weeds are not controlled at these rates. Perennial grasses approved for the Conservation Reserve Program (CRP) may be planted 9 mo after applying pronamide. Do not use any tillage after application in the fall.
Caution  A restricted-use herbicide. A 12-mo wait is required after application before planting winter wheat, barley, or oats.
Site of action  Group 3: microtuble assembly inhibitor
Chemical family  Benzamide