Alfalfa Seed
Bob Parker
Revised October 31, 2008

Note: Several herbicides labeled for alfalfa grown for seed are not registered for alfalfa grown for forage.
ALFALFA SEED—Annual Grass and Broadleaf Weeds in New Seedings
•  benefin (Balan DF)
Rate  1.2 to 1.5 lb ai/A
Time  Apply before planting to a clean, clod-free soil surface and incorporate 2 to 3 inches deep within 4 hr after application.
Remarks  Use lower rates on coarse and medium soils, higher rates on fine soil. Avoid overlapping spray.
Caution  Do not plant wheat, barley, rye, other domestic grasses, or onions for 10 mo after application. Do not plant milo (grain sorghum), corn, oats, sugar beets, other root crops, or spinach for 12 mo after application.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  EPTC (Eptam)
Rate  2 to 4 lb ai/A
Time  Apply before planting and incorporate immediately and thoroughly into soil.
Remarks  Use lower rate on sandy soils, higher rate on silty and clay soils, quackgrass, and nutsedge. Incorporate 2 to 3 inches deep with power-drive rotary tiller for band or broadcast application, or set tandem disk 4 to 6 inches deep and use twice at right angles for broadcast application.
Caution  Crop may be injured temporarily. Do not use if a grass or grain companion crop is to be planted with the alfalfa.
Site of action  Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family  Thiocarbamate
•  trifluralin (Treflan HFP)
Rate  0.5 to 0.75 lb ai/A
Time  Before planting, apply and thoroughly incorporate into the top 2 to 3 inches of soil.
Remarks  Use lower rates on coarse and medium soils, higher rates on fine soils.
Caution  Some crop stand reduction and stunting may occur with this use. Do not plant sugar beets, red beets, spinach, proso millet, corn, sorghum, oats, or annual or perennial grass crops or grass mixtures for 12 mo after a spring application or 14 mo after a fall application. Moldboard plowing 12 inches deep before planting reduces the possibility of crop injury. If land has not been irrigated, do not plant these crops for 18 mo after a spring application or 20 mo after a fall application.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  pendimethalin (Prowl) 
Rate  0.475 to 0.95 lb ai/A (1 to 2 pints/A of Prowl H2O)
Time  Apply to alfalfa with two trifoliate leaves but before it is 6 inches tall between January 15 and April 30 and before weeds emerge.
Remarks  Controls most annual grasses and certain broadleaf weeds, in addition to dodder, as they germinate. Processed seed must be labeled “Not for human or animal consumption” at the processing plant, and all seed screenings must be disposed so that they cannot be distributed or used for food or feed. For optimum dodder control, use 3 to 4 quarts/A of Prowl H2O. 
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  imazethapyr (Pursuit)
Rate  0.047 to 0.094 lb ai/A (1.08 to 2.16 oz/A Pursuit DG)
Time  Apply after seedling alfalfa has reached second trifoliate growth stage and when most weeds are actively growing and 1 to 3 inches tall or across.
Remarks  Adding an adjuvant (nonionic surfactant or crop oil concentrate) and a liquid fertilizer solution is required. Temporary height reduction or slight leaf yellowing may occur soon after application. Weeds under stress are less susceptible to control. Apply at least 1 hr before rain or overhead irrigation.
Caution  Do not feed, graze or harvest alfalfa for 30 days after application. Consult recropping restrictions before using. Some rotation crops cannot be planted within 40 mo of application. Only rotational crops harvested at maturity may be used for feed or food.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  imazamox (Raptor)
Rate  0.03125 to 0.047 lb ai/A (4 to 6 oz/A Raptor)
Time  Apply after seedling alfalfa has at least two fully expanded trifoliate leaves and when the most weeds are 1 to 3 inches tall or across and before alfalfa buds form.
Remarks  Adding an adjuvant (nonionic surfactant or crop oil concentrate) and a liquid fertilizer or ammonium sulfate solution enhances weed control. Temporary height reduction or leaf yellowing may occur soon after application. Weeds under stress are harder to control. Apply at least 1 hr before rain or overhead irrigation
Caution  Note recropping restrictions before using. Some crops cannot be planted within 26 mo of application.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
ALFALFA SEED—Annual Broadleaf Weeds in New Stands
•  2,4-DB (Butyrac or Butoxone)
Rate  0.5 to 1.5 lb ae/A
Time  Apply postemergence to small seedling weeds less than 3 inches tall and when alfalfa seedlings have two to four trifoliate leaves.
Remarks  Controls broadleaf weeds only, not grasses. Use higher rate in low-humidity areas. Using 2,4-DB is progressively more damaging to alfalfa as it matures. Certain annual broadleaf weeds such as smartweed, prostrate knotweed, redroot pigweed, and chickweed are resistant.
Caution  Do not graze seedling alfalfa within 60 days after application.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  bromoxynil (Buctril)
Rate  0.25 to 0.375 lb ai/A or 0.5 lb ai/A when applied through sprinkler irrigation
Time  Apply in fall or spring when alfalfa has at least two trifoliate leaves and weeds listed as susceptible or moderately susceptible have no more than four leaves and are no more than 2 inches tall or 1 inch wide.
Remarks  For broadleaf weeds only. Crop may be stunted temporarily, but yields should not drop.
Caution  Do not treat when temperature exceeds or is expected to exceed 70°F in the 3 days after application by ground or exceeds 85°F if applied through sprinkler irrigation systems; crop injury may be unacceptable. Do not add a surfactant or crop oil because crop injury may increase. Do not cut for feed or graze for 30 days after application.
Site of action  Group 6: photosystem II inhibitor
Chemical family  Nitrile
•  bentazon (Basagran)
Washington and Oregon only
Rate  1 lb ai/A
Time  Apply when mayweed chamomile (dog fennel) rosettes are 1 to 3 inches wide and alfalfa has at least two trifoliate leaves.
Remarks  Special local needs labels WA-900012 and OR-950033AB. Apply by ground or air when weeds are small. Use 1 quart/A of crop oil concentrate.
Caution  Do not apply if alfalfa shows injury from previous herbicide applications or during drought or cold weather. Do not tank-mix with other pesticides or fertilizers. Do not apply through any type of irrigation system. Do not use any portion of the treated alfalfa plant for forage, hay, or seed, or use seed screenings for food or feed.
Site of action  Group 6: photosystem II inhibitor
Chemical family  Benzothiadiazole
ALFALFA SEED—Annual Grass Weeds in New Stands
•  sethoxydim (Poast or Poast Plus)
Rate  0.19 to 0.47 lb ai/A
Time  Apply to actively growing annual or perennial grasses at growth stage listed on label.
Remarks  Controls grasses only. See label for specific herbicide rates and weed species and size. Always add a nonphytotoxic oil concentrate to the spray tank at 2 pints/A. Sethoxydim is most effective on actively growing grasses before they have been cut but before they reach the maximum size indicated on the label. Larger, more mature grasses can be controlled, but two applications may be required. Will not control annual bluegrass or any of the fine fescues.
Caution  Control often is erratic on grasses stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors. Do not apply if rain is expected within 1 hr after application. Do not exceed 0.94 lb ai/A in one season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  fluazifop (Fusilade DX)
Rate  0.125 to 0.188 lb ai/A (0.5 to 0.75 pint/A product)
Time  Apply to actively growing grasses when susceptible grasses are in labeled growth stage.
Remarks  Controls grasses only. Special local needs labels OR-040006, ID-950006, and WA-040007. Add a crop oil concentrate at 0.5% to 1% concentration or a nonionic surfactant at 0.25% to 0.5% concentration. Results often are erratic on grasses stressed from lack of vigor, drought, high temperatures, low fertility, or other factors. More mature grasses and quackgrass can be controlled, but may require two applications. Annual bluegrass and all fine fescues are not controlled. Fluazifop-P is often weak on the foxtails and perennial bluegrass.
Caution  Do not feed treated forage to livestock. No part of the treated field, including seed, seed screenings, hay, forage, or stubble may be used for human or animal feed.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  clethodim (Select 2EC, Select Max, Intensity or Intensity One)
Rate  Select, Select 2EC, or Intensity—use 0.094 to 0.125 lb ai/A (6 to 8 fl oz/A product). Select Max or Intensity One—use 0.07 to 0.24 lb ai/A (9 to 32 fl oz/A product).
Time  Apply to actively growing annual or perennial grasses at growth stage listed on label.
Remarks  For grass control only. Refer to label for specific weed species and weed size. Always add a crop oil concentrate containing at least 15% emulsifier at 1% v/v in the finished spray volume. Clethodim is most effective on actively growing grasses before they reach maximum size indicated on label. For best results in irrigated alfalfa, apply within 2 to 4 days after irrigation. Use at least 0.125 lb ai/A (8 oz/A of Select) or 0.129 lb ai/A (17 oz/A of Select Max) to control annual bluegrass.
Caution  Control may be erratic if grasses are stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors, or if grasses are larger than indicated on label. Do not apply if rain is expected within 1 hr after application. Do not apply within 15 days of grazing, feeding, or harvesting for forage or hay. Do not exceed 0.5 lb ai/A per season (32 fl oz/A of Select or 64 fl oz/A of Select Max)
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  quizalofop (Assure II)
Rate  0.034 to 0.825 lb ai/A (5 to 12 oz/A product)
Time  Apply to actively growing annual or perennial grasses at growth stage listed on label.
Remarks  See label for specific herbicide rates, weed species, and weed size. Under arid conditions, use higher rate for the target grass weed. Always include a nonphytotoxic crop oil concentrate at 1% v/v or a nonionic surfactant at 0.25% v/v. Crop oil concentrate is preferred in arid areas. Will not control annual bluegrass or fine fescue. Control may be reduced on grasses stressed from lack of moisture, cold weather, herbicide injury, and insect injury or disease.
Caution  Do not apply within 14 days of anticipated bloom. Do not use any part of crop (seed, sprouts, screenings, hay, forage, etc.) for animal or human consumption. Do not exceed two applications or 0.17 lb ai/A (25 oz/A product) per season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
ALFALFA SEED—Summer Annual Grasses in Established Stands
•  trifluralin (Treflan TR-10)
Rate  2 lb ai/A
Time  Apply before weeds emerge.
Remarks  Within 3 days, trifluralin must be activated by a single rain or overhead sprinkler irrigation of 0.5 inch after application, or mechanically incorporated with equipment that will ensure thorough soil mixing with minimum damage to the alfalfa. Will not control emerged weeds.
Caution  If established alfalfa is to be rotated to another crop the year after application, plant only those crops for which trifluralin can be applied as a preplant treatment, or injury may result.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  sethoxydim (Poast or Poast Plus)
Rate  0.19 to 0.47 lb ai/A
Time  Apply to actively growing annual or perennial grasses at growth stage listed on the label.
Remarks  See label for specific herbicide rates, weed species, and weed size. Always add a nonphytotoxic oil concentrate to the spray tank at 2 pints/A of alfalfa treated. Sethoxydim is most effective on actively growing grasses before they have been cut and before they reach the maximum size indicated on the label. Larger, more mature grasses can be controlled, but two applications may be required. Will not control annual bluegrass or any of the fine fescues.
Caution  Control often is erratic on grasses stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors. Do not apply if rain is expected within 1 hr after application. Do not exceed 0.94 lb ai/A in one season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  fluazifop (Fusilade DX)
Rate  0.125 to 0.188 lb ai/A (0.5 to 0.75 pint/A product)
Time  Apply to actively growing susceptible grasses in the labeled growth stage.
Remarks  Special local needs labels OR-040006, ID-950006, and WA-040007. Add a crop oil concentrate at 0.5% to 1% concentration or a nonionic surfactant at 0.25% to 0.5% concentration. Results often are erratic on grasses stressed from lack of vigor, drought, high temperatures, low fertility, or other factors. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescues are not controlled. Fluazifop is often weak on the foxtails and perennial bluegrass.
Caution  Do not feed treated forage to livestock.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  quizalofop (Assure II)
Rate  0.034 to 0.825 lb ai/A (5 to 12 oz/A product)
Time  Apply to actively growing annual or perennial grasses in the labeled growth stage.
Remarks  See label for specific herbicide rates, weed species, and weed size. Under arid conditions, use higher rate for the target grass weed. Always include a nonphytotoxic crop oil concentrate at 1% v/v or a nonionic surfactant at 0.25% v/v. Crop oil concentrate is preferred in arid areas. Will not control annual bluegrass or fine fescue. Control may be reduced on grasses stressed from lack of moisture, cold, herbicide injury, or insect injury or disease.
Caution  Do not apply within 14 days of anticipated bloom. Do not use any part of crop (seed, sprouts, screenings, hay, forage, etc.) for animal or human consumption. Do not exceed two applications or 0.17 lb ai/A (25 oz/A product) per season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  clethodim (Select, Select 2EC, Select Max, Intensity, or Intensity One)
Rate  Select, Select 2EC, or Intensity—use 0.094 to 0.125 lb ai/A (6 to 8 fl oz/A product). Select Max or Intensity One—use 0.07 to 0.24 lb ai/A (9 to 32 fl oz/A product).
Time  Apply to actively growing annual or perennial grasses in the labeled growth stage.
Remarks  For grass control only. See label for specific weed species and weed size. Always add a crop oil concentrate containing at least 15% emulsifier at 1% v/v in the finished spray volume. Adding ammonium sulfate improves control of difficult-to-control grasses. Clethodim is most effective on actively growing grasses before they reach maximum size indicated on label. Use higher rate under heavy grass pressure and/or if annual bluegrass is more mature.
Caution  Control may be erratic on grasses stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors, or if grasses are larger than indicated on label. Do not apply if rain is expected within 1 hour after application. Do not apply within 15 days of grazing, feeding, or harvesting for forage or hay. Do not exceed 0.5 lb ai/A per season (32 fl oz/A of Select or 64 fl oz/A of Select Max)
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
ALFALFA SEED—Quackgrass, Volunteer Grains, and Annual Grasses in New or Established Stands
•  pronamide (Kerb)
Rate  1 to 2 lb ai/A
Time  Apply October through early December.
Remarks  Results are best if applied under cool conditions (55°F or cooler) and followed by rain or overhead irrigation. Use the higher rates for perennial grass control. On fields to be treated, remove residue by burning or tilling into the soil.
Caution  Restricted-use herbicide. Apply on new plantings only after alfalfa has reached the first trifoliate-leaf stage of growth. Do not apply preplant, preemergence, or in the seed-leaf stage. Do not graze treated fields or feed clippings and crop residues to livestock within 25 days of application (if less than 1.5 lb ai/A) or within 45 days (if 1.5 to 2 lb ai/A). Do not apply on frozen ground.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Benzamide
•  fluazifop (Fusilade DX)
Rate  0.125 to 0.188 lb ai/A (0.5 to 0.75 pint/A product)
Time  Apply to actively growing susceptible grasses in the labeled growth stage.
Remarks  Special local needs labels OR-040006, ID-950006, and WA-040007. Add a crop oil concentrate at 0.5% to 1% concentration or a nonionic surfactant at 0.25% to 0.5% concentration. Results often are erratic on grasses stressed from lack of vigor, drought, high temperatures, low fertility, or other factors. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescues are not controlled. Fluazifop is often weak on the foxtails and perennial bluegrass.
Caution  Do not feed treated forage to livestock.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  sethoxydim (Poast or Poast Plus)
Rate  0.19 to 0.47 lb ai/A
Time  Apply to actively growing annual or perennial grasses in the labeled growth stage.
Remarks  See label for specific herbicide rates, weed species, and weed size. Always add a nonphytotoxic oil concentrate to spray tank at 2 pints/A. Most effective on actively growing grasses before they are cut or reach the maximum size indicated on label. Larger, more mature grasses can be controlled, but two applications may be required. Will not control annual bluegrass or any of the fine fescues.
Caution  Control often is erratic on grasses stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors. Do not apply if rain is expected within 1 hr after application. Do not exceed 0.94 lb ai/A in one season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  clethodim (Select, Select 2EC, Select Max, Intensity, or Intensity One)
Rate  Select, Select 2EC, or Intensity—use 0.094 to 0.25 lb ai/A (6 to 16 fl oz/A product). Select Max or Intensity One—use 0.07 to 0.24 lb ai/A (9 to 32 fl oz/A product).
Time  Apply to actively growing annual or perennial grasses in the labeled growth stage.
Remarks  Controls grass only but weak on quackgrass. Refer to label for specific weed species and weed size. Always add a crop oil concentrate containing at least 15% emulsifier, at 1% v/v, in the finished spray volume. Adding ammonium sulfate improves control of difficult-to-control grasses. Most effective on actively growing grasses before they reach the maximum size listed on label. For best results in irrigated alfalfa, apply within 2 to 4 days after an irrigation. Use higher rate under heavy grass pressure and/or when annual bluegrass is more mature.
Caution  Control may be erratic on grasses stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors, or if grasses are larger than indicated on label. Do not apply if rain is expected within 1 hr after application. Do not apply within 15 days of grazing, feeding, or harvesting for forage or hay. Do not exceed 0.5 lb ai/A per season (32 fl oz/A of Select or 64 fl oz/A of Select Max).
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  quizalofop (Assure II)
Rate  0.034 to 0.825 lb ai/A (5 to 12 oz/A product)
Time  Apply to actively growing annual or perennial grasses in the labeled growth stage.
Remarks  See label for specific herbicide rates, weed species, and weed size. Under arid conditions, use higher rate for the target grass weed. Always include a nonphytotoxic crop oil concentrate at 1% v/v or a nonionic surfactant at 0.25% v/v. Crop oil concentrate is preferred in arid areas. Will not control annual bluegrass or fine fescue. Control may be reduced on grasses stressed from lack of moisture, cold, herbicide injury, or insect injury or disease.
Caution  Do not apply within 14 days of anticipated bloom. Do not use any part of crop (seed, sprouts, screenings, hay, forage, etc.) for animal or human consumption. Do not exceed two applications or 0.17 lb ai/A (25 oz/A product) per season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
breakhere  ALFALFA SEED—Winter Annual Grasses and Broadleaf Weeds in Established Stands
•  paraquat (Gramoxone Inteon or Firestorm)
Rate  Firestorm—use 0.49 to 1 lb ai/A (1.3 to 2.7 pints/A product). Gramoxone Inteon—use 0.25 to 0.375 lb ai/A (2 to 3 pints/A product). Add nonionic surfactant with at least 75% surface-active agent at 16 to 32 fl oz/100 gal, or crop oil concentrate with 15 to 20% approved emulsifier at 1 gal/100 gal spray mix.
Time  Apply after seed harvest when crop is dormant, before spring growth starts.
Remarks  Apply soon after weeds germinate. Alfalfa should be dormant and regrowth following harvest not more than 2 inches high. Control decreases as weed size increases. Use 20 gal/A or more of water carrier for ground application. Paraquat is a contact herbicide. Combining with one of the residual herbicides usually gives knockdown plus residual control.
Caution  Restricted-use herbicide. Do not pasture animals in treated fields. Do not graze, cut, or harvest within 42 days of application. Do not apply more than once per season. Follow safety precautions on the labels.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  pendimethalin (Prowl or Stealth) 
Rate  Prowl H2O —use 1 to 3.8 lb ai/A (1 to 4 quarts/A product). Prowl 3.3EC and Stealth—use 1 to 4 lb ai/A (1.2 to 4.8 quarts/A product).
Time  Apply to established alfalfa between January 15 and April 30 but before dodder germinates.
Remarks  Active special local needs labels include OR-000030 (A and B) and OR-070027 for Prowl 3.3, WA-070002 for Prowl H2O, and ID-060016 and OR-070027 for Stealth. Controls most annual grasses and certain broadleaf weeds, in addition to dodder, as they germinate. Processed seed must be labeled “Not for human or animal consumption” at the processing plant, and all seed screenings must be disposed of in a way that they cannot be distributed or used for food or feed. For optimum dodder control, use 3 to 4 quarts/A of Prowl H2O or 3 to 4.8 quarts/A of Prowl 3.3 or Stealth. 
Caution  Do not apply this rate to seedling alfalfa. Do not graze or harvest alfalfa for hay after application. Do not use screenings from seed processing as feed for livestock. Do not use harvested seed for sprouting. Refer to main labels for crop rotation restrictions.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  diuron (Karmex or Direx)
Rate  1.2 to 2.4 lb ai/A
Time  Apply at start of dormancy (late October through early December).
Remarks  Apply as a broadcast spray to dormant alfalfa established more than 1 yr. Not very effective on downy brome (cheatgrass) or volunteer cereals.
Caution  Do not use on soils with less than 1% organic matter. Do not apply to snow-covered or frozen soil. Do not replant treated area to any crop within 2 yr of application. 
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  hexazinone (Velpar DF)
Walla Walla County, WA only 
Rate  1 to 1.5 lb ai/A
Time  Apply in fall after crop is dormant and before spring growth exceeds 2 inches. 
Remarks  Use lower rate on coarse, sandy soils low in organic matter (refer to labels WA-060012 and WA-060013). Apply to alfalfa established at least one growing season. Results are best if applied before or soon after weeds emerge (before weeds are 2 inches tall or across). If weeds are emerged, use a surfactant.
Caution  Do not graze or harvest (cut for hay) within 30 days after application. Do not apply to alfalfa growing under stress from insect, disease, winter injury, or other factors. Do not use on fields with sandy loam or loamy sands having less than 1% organic matter. Very heavy rain or more than 0.5 inch of irrigation soon after application may result in crop injury or herbicide nonperformance. Hexazinone persists in soil up to 24 mo. Read label for crop rotation restrictions and other cautions.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazinone
•  simazine (Clean Crop or Simazine 4L)
Washington only
Rate  0.8 to 1.6 lb ai/A
Time  Apply to alfalfa in fall after harvest but before ground freezes.
Remarks  Special local needs label WA-900040. Broadcast spray on alfalfa established 1 yr or more. Do not apply to frozen ground. Apply only once per year. Processed seed must be labeled “Not for human or animal consumption” at the processing plant, and all seed screenings must be disposed of in a way that they cannot be distributed or used for food or feed.
Caution  Do not use on sand, loamy sand, or gravelly soil. Do not use seed for sprouting. Do not graze treated area or cut for hay after treatment. Do not cultivate before or after simazine application. Do not plant any crop except corn the year after application, or crop may be injured.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazine
•  terbacil (Sinbar)
Rate  0.4 to 1.2 lb ai/A
Time  Apply to dormant alfalfa after frost before January 1.
Remarks Broadcast spray on dormant alfalfa established 1 yr or more. Use lower rate on coarse, sandy soils or on soils low in organic matter.
Caution  Do not use on sand, loamy sand, or gravelly soil. Do not use on soils containing less than 1% organic matter. Do not apply on snow-covered or frozen ground. Do not replant treated areas to any crop within 2 yr of last application.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Uracil
•  imazethapyr (Pursuit)
Rate  0.047 to 0.094 lb ai/A (1.08 to 2.16 oz/A Pursuit DG)
Time  Apply to established alfalfa in the fall, in spring to dormant, or semidormant alfalfa (less than 3 inches of regrowth), and when most weeds are actively growing and 1 to 3 inches tall or across.
Remarks  Adding an adjuvant (nonionic surfactant or crop oil concentrate) and a liquid fertilizer solution is required. Temporary height reduction or slight leaf yellowing may occur soon after application. Weeds under stress are less susceptible to control. Apply at least 1 hr before rain or overhead irrigation.
Caution  Do not feed, graze, or harvest alfalfa for 30 days after application. See recropping restrictions before use. Some crops cannot be planted within 40 mo of application. Use only rotational crops harvested at maturity for feed or food.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  imazamox (Raptor)
Rate  0.03125 to 0.047 lb ai/A (4 to 6 oz/A Raptor)
Time  Apply to established alfalfa in the fall, in the spring to dormant or semidormant alfalfa (less than 3 inches of regrowth), and when most weeds are 1 to 3 inches tall or across and before alfalfa buds form.
Remarks  Adding an adjuvant (nonionic surfactant or crop oil concentrate) and a liquid fertilizer solution or ammonium sulfate solution enhances weed control. Temporary height reduction or leaf yellowing may occur soon after application. Weeds under stress are harder to control. Apply at least 1 hr before rain or overhead irrigation.
Caution  Before using, note recropping restrictions. Some crops cannot be planted within 26 mo of application.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  metribuzin (Sencor, TriCor)
Rate  0.25 to 1 lb ai/A
Time  Apply in fall after crop is dormant and before spring growth starts.
Remarks  Consult label for the product used. Broadcast spray dormant alfalfa established 1 yr or more. Use the 0.25-lb rate of Sencor if common chickweed is the only target. 
Caution  Do not use on sand or use Sencor on soils with a pH greater than 8.2. Do not apply on snow-covered or frozen ground. Use lower rates on coarse, sandy soils or soils low in organic matter. Do not graze or harvest within 28 days after application. Stunting and chlorosis may occur, particularly in nondormant alfalfa. Stress—which may be caused in part by low fertility, disease, insects, overcutting, drought, or frost—may increase the possibility of crop injury. Avoid overlapping because injury may occur. See herbicide label for recropping recommendations.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazinone
•  norflurazon (Zorial)
Rate  1 to 2 lb ai/A
Time  Apply no earlier than 5 mo after crop emerges, or to dormant alfalfa before weeds emerge.
Remarks  Use lower rates on coarse and medium soils, higher rate on fine soils. At least 0.5 inch of overhead moisture is needed to move herbicide into soil. Fall or winter application recommended in nonirrigated areas with less than 15 inches annual moisture (rain and snow combined) or less than 4 inches of spring rain. Does not control established weeds. Established weeds or weeds that emerge before activation may be controlled with a labeled postemergence herbicide.
Caution  Do not apply to seedling alfalfa earlier than 5 mo after planting. Do not exceed 2 lb ai/A per year. Note rotation restrictions. Bioassay soils containing more than 65% sand before crop rotation. Rotation crops can be planted if no signs of phytotoxicity are observed in bioassay plants for 4 mo after emergence.
Site of action  Group 12: bleaching; inhibitor of carotenoid biosynthesis
Chemical family  Pyridazinone
•  flumioxazin  (Chateau)
Rate  2 oz ai/A (4 oz product/A)
Time  Apply preemergence to the weeds.
Remarks  Applications should be made as soon as possible after cutting and removing alfalfa to minimize crop injury. Flumioxazin will burn treated leaves and stems. A second application can be made 60 days after the first application. Will only give fair control of many annual grasses. If weeds are present when applications are made after the last harvest in the fall or when the alfalfa is dormant, apply with paraquat to burndown weeds present.
Caution  Do not harvest or graze within 25 days of application. Do not make second application within 60 days of the first application. Do not exceed 8 oz of Chateau during a single growing season.
Site of action  Group 14: protoporphyrinogen oxidase (PPO) inhibitor
Chemical family  N-phenylphthalimide
•  S-metolachlor (Dual Magnum)
Oregon only
Rate  2.5 to 3.2 lb ai/A (2.5 to 3.2 lb product/A) 
Time Apply and incorporate prior to weed emergence. 
Remarks SLN OR-040007. This is an indemnified label that is available at www.farmassist.com. Users of this product assume all risk of crop injury, crop yield reduction and crop loss and releases Syngenta Crop Protection from all liability. Incorporate metolachlor uniformly in the top 3 inches the soil by cross tillage (twice over the field).
Caution Do not use tailwater from first flood or furrow irrigation of treated fields to treat nontarget crops, unless 0.5 inch of rainfall has occurred between application and the first irrigation. No portion of the crop may be may be used or distributed for food or feed for 1 year after application. All seed screenings must be disposed of in such a manner that the screenings cannot be distributed for food or feed purposes.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Chloroacetamide
ALFALFA SEED—Dodder and Other Weeds in Established Stands 
•  pendimethalin (Prowl) 
Rate  2 to 4 lb ai/A
Time  Apply to established alfalfa between January 15 and April 30 but before dodder germinates.
Remarks  Active special local needs labels include WA-920034, ID-930012, and OR-000030 for Prowl 3.3 and ID-060006, OR-060005, and WA-070002 for Prowl H2O. Controls most annual grasses and, in addition to dodder, certain broadleaf weeds as they germinate. Processed seed must be labeled “Not for human or animal consumption” at the processing plant, and all seed screenings must be disposed of in a way that they cannot be distributed or used for food or feed.
Caution  Do not apply to seedling alfalfa. Do not graze or harvest alfalfa for hay after application. Do not use screenings from seed processing as feed for livestock. Do not use harvested seed for sprouting.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  pronamide (Kerb)
Rate  1.5 to 2 lb ai/A. Use 1.5 to 2 lb ai/A in furrow-irrigated or rill-irrigated fields and 1.5 lb ai/A in sprinkler-irrigated fields.
Time  Apply in spring before dodder germinates.
Remarks  On furrow-irrigated or rill-irrigated fields, follow a shallow incorporation with irrigation within 7 days. On sprinkler-irrigated fields, should be follow application with 0.5 to 1 inch of water within 1 to 3 days. Seldom is dodder controlled 100%. Patrol fields to find dodder patches, then spot-treat them.
Caution  Restricted-use herbicide. Follow application with a shallow irrigation. When sprinkler irrigation is used, irrigate within 3 days; with furrow systems, irrigate within 7 days. Do not graze treated fields or harvest for forage.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Benzamide
•  trifluralin (Treflan TR-10)
Rate  3 to 4 lb ai/A (30 to 40 lb/A Treflan TR-10 granules)
Time  Apply before dodder germinates in late winter or spring. The surface-applied granules must be activated by a single rain or overhead sprinkler irrigation of at least 0.5 inch within 3 days of application; otherwise, incorporate with equipment that ensures thorough soil mixing with minimal damage to the alfalfa.
Remarks  Special local needs labels ID-910001, OR-900019 (A and B), and WA-900016. Use only on alfalfa grown for seed. Seed must be labeled at the processing plant “Not for human or animal consumption.” Seed screenings from alfalfa treated with more than 20 lb/A Treflan TR-10 must be disposed of in a way that prevents recovery for food or feed.
Caution  Do not use on seedling alfalfa. Do not graze or harvest treated alfalfa for hay. When treated alfalfa will be rotated to another crop in the year after application, plant only those crops to which trifluralin can be applied as a preplant treatment.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
ALFALFA SEED—Spot Treatment of Dodder
•  glyphosate
Rate  0.5 lb ae/A
Time  Apply to actively growing dodder.
Remarks  Research has shown that lower rates will control dodder.
Caution  Do not spray more than 10% of field to be harvested. Alfalfa will be injured or killed in treated areas. Do not graze or harvest within 14 days after application.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
ALFALFA SEED—Nightshade and Dodder  in Established Stands
•  ethalfluralin (Sonalan HFP)
Rate  1.5 to 1.7 lb ai/A before nightshade germinates; 1.5 lb ai/A before dodder germinates
Time  Apply 1.5 to 1.7 lb ai/A (4 to 4.5 pints/A) before nightshade germinates and thoroughly incorporate into the top 2 to 3 inches of soil. Apply again in the spring, at 1.5 lb ai/A (4 pints/A), before dodder germinates.
Remarks  Special local needs labels ID-950020, OR-940037, and WA-940018. In Oregon, use only on alfalfa grown for seed in Malheur, Umatilla, Morrow, Josephine, and Jackson counties by members of the Oregon Alfalfa Seed Growers Assn., Gardena Alfalfa Seed Growers Assn., Inc., and Josephine Growers Cooperative Assn. For best results, herbicide should be activated within 2 days after application. For dodder control, herbicide may be activated by rain, irrigation, or mechanical incorporation, but do not mechanically incorporate more than 1 inch deep.
Caution  Do not apply the year before rotating to another crop. Do not apply to seedling alfalfa (up to six-true-leaf stage) or to soils that are wet, cloddy, or subject to prolonged flooding.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
ALFALFA SEED—Perennial Weed Control (Quackgrass, Field Bindweed, Canada Thistle, Johnsongrass, etc.)
•  glyphosate
Rate  2.25 to 3.75 lb ae/A. For nonsodded quackgrass, use 0.75 to 1.5 lb ae/A. For sodded quackgrass, use 1.5 to 2.25 lb ae/A.
Time  Apply preplant to full-grown weeds at least 10 days before planting crop or as a spot treatment in the crop. See label for growth stage of perennial weeds.
Remarks  Use highest rate on field bindweed.
Caution  Do not apply to weeds stressed by drought, weather, or maturity. Rain within 6 hr after application may reduce effectiveness. Control weed escapes the following years. If used as a spot treatment in the growing crop, do not treat more than 10% of the field. Do not harvest or graze within 14 days after treatment.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted

Birdsfoot Trefoil
Bob Parker
Revised October 16, 2008
•  2,4-DB (Butyrac or Butoxone)
Rate  0.5 lb ae/A
Time  Apply after trefoil has at least two true leaves.
Remarks  Controls certain annual broadleaf weeds in new stands. Weeds should be small at the time of application.
Caution  Observe the same precautions with 2,4-DB as for 2,4-D. Leaves in trefoil might distort for several weeks after application, lowering production. This treatment damages established stands. Do not graze or feed treated forage for 60 days after treatment.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  glyphosate (several trade names)
Rate  2.25 to 3.75 lb ae/A
Time  Apply preplant to full-grown weeds at least 10 days before planting the crop. (Refer to label for growth stage of perennial weeds.)
Remarks  Controls weeds before trefoil establishes. Use highest rate on field bindweed.
Caution  Do not apply to weeds stressed by drought, weather, or maturity. Rain within 6 hours after application may reduce effectiveness. Control weed escapes the next year.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  pronamide (Kerb)
Rate  0.75 to 1.5 lb ai/A
Time  Apply in fall after trefoil has three to four trifoliate leaves but before soil freezes. December applications are preferred.
Remarks  Controls annual grasses and volunteer cereals. Use higher rate for established grasses. Does not control broadleaf weeds in the composite family.
Caution  A restricted-use herbicide. Do not graze treated field or harvest for forage within 120 days after treatment. Soil residues of pronamide persist; therefore, do not plant cereals or a grass crop immediately following clovers that were winter killed.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Benzamide
•  EPTC (Eptam)
Rate  2 to 4 lb ai/A
Time  Apply to seedbed before final disking and harrowing.
Remarks  Preemergence control of annual grass and broadleaf weeds in new plantings. Apply to seedbeds dry enough to permit thorough mixing by disking two directions immediately after spraying. Seeding can be right after herbicide incorporation.
Caution  Avoid contact with clothing.
Site of action  Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family  Thiocarbamate
•  benefin (Balan)
Rate  0.75 to 1.5 lb ai/A. In Idaho, use 1.12 to 1.5 lb ai/A.
Time  Apply up to 10 wk preplant. Do not apply after seeding.
Remarks  For preemergent control of annual grasses and broad-leaf weeds in new plantings. Use lower rate in sandy soils. Use double cross-disking or a rototiller to incorporate herbicide immediately after application.
Caution  Avoid spray overlaps. Do not plant wheat, barley, rye, grasses, or onions for 10 mo after application. Wait 12 mo before seeding corn, oats, red beets, root crops, or spinach.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  diuron (Karmex or others)
western Oregon only
Rate  1.6 lb ai/A
Time  Apply after trefoil is dormant, in late October or early November.
Remarks  Controls annual grasses and broadleaf weeds in established trefoil. Use mechanical agitation.
Caution  Apply only on stands at least 1 yr old. Diuron is a soil sterilant at high rates, so take care to avoid double applications.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  sethoxydim (Poast)
Rate  0.28 to 0.47 lb ai/A (1.5 to 2.5 pints/A Poast)
Time  To control grasses listed on label. Apply to actively growing grasses at the appropriate stage as listed on the label.
Remarks  Always add a nonphytotoxic oil concentrate to the spray tank at 2 pints/A.
Caution  Do not apply to drought-stressed grass or grass that has gone through an extended dry period. Do not allow grazing until 7 days after application, and do not cut for dry hay until 14 days after application.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  clethodim (Select, Select 2EC, Select Max, Intensity, or Intensity One)
Rate  Select, Select 2EC, or Intensity—use 0.094 to 0.25 lb ai/A (6 to 16 fl oz/A product). Select Max or Intensity One—use 0.07 to 0.24 lb ai/A (9 to 32 fl oz/A product).
Time  Apply to actively growing annual or perennial grasses at growth stage listed on label.
Remarks  For grass control only. Weak on quackgrass. See label for specific weed species and weed size. Always add a crop oil concentrate containing at least 15% emulsifier, at 1% v/v, in the finished spray volume. Adding ammonium sulfate improves control of difficult-to-control grasses. Clethodim is most effective on actively growing grasses before they reach the maximum size indicated on label. Use the higher rate under heavy grass pressure and/or when annual bluegrass is more mature.
Caution  Control may be erratic if grasses are stressed by drought, temperature extremes, insect damage, herbicide injury, or other factors, or if grasses are larger than indicated on label. Do not apply if rain is expected within 1 hr after application. Do not apply within 15 days of grazing, feeding, or harvesting for forage or hay. Do not exceed 0.5 lb ai/A per season (32 fl oz/A of Select or 64 fl oz/A of Select Max).
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
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