Winter Annual Grasses and Broadleaf Weeds in Established Stands

carfentrazone (Aim EC)

Rate 0.008 to 0.04 lb ai/a (0.5 to 2.5 oz/a Aim EC)

Time Apply in the fall after the alfalfa is dormant or in spring before spring growth.

Remarks Broadcast applications are to be made to dormant alfalfa established for at least 1 year. See the Airm EC label for recommended adjuvants.

Caution Do not apply more than 2.5 oz/a of Aim EC per year.

Site of Action Group 14: Protoporphyrinogen oxidase inhibitor

Chemical family Triazolinone

diuron (Karmex or Direx)

Rate 1.2 to 2.4 lb ai/a (1.5 to 3 lb/a product)

Time Apply at start of dormancy (late October through early December).

Remarks Apply as a broadcast spray to dormant alfalfa established more than 1 year. Not very effective on downy brome (cheatgrass), or on volunteer cereals.

Caution Do not use on soils with less than 1% organic matter. Do not apply to snow-covered or frozen soil. Consult label on replant timing as labels and rates vary.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

flumioxazin (Chateau)

Rate 0.1275 lb ai/a (4 oz /a Chateau)

Time Apply preemergence to the weeds.

Remarks To minimize crop injury, applications should be made as soon as possible after cutting and removing alfalfa. 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

hexazinone (Velpar DF)

Special precautions are needed for use on seed crops in Walla Walla County in Washington. See Section F, Alfalfa Seed

Rate 0.45 to 1.5 lb ai/a (0.67 to 2 lb/a Velpar)

Time Apply in fall after crop is dormant and before spring growth starts. On nondormant and semidormant varieties, apply in winter when alfalfa is least actively growing.

Remarks Labels differ slightly between Velpar formulations. Use lower rate on coarse, sandy soils low in organic matter. Apply to alfalfa established at least one growing season but not on snow-covered or frozen ground. Results are best if applied before or soon after weeds emerge (before weeds are 2 inches tall or across).

Caution Do not graze or harvest within 30 days after application. Do not apply to alfalfa growing under stress from insect, disease, winter injury, or other factors. Very heavy rain or irrigation soon after application may result in crop injury or nonperformance of the herbicide. Hexazinone persists in soil up to 24 months. Read label for crop rotation restrictions and other cautions.

Site of action Group 5: photosystem II inhibitor

Chemical family Triazinone

metribuzin (Dimetric EXT, TriCor DF, TriCor 4F, Metribuzin 75)

Rate 0.25 to 1 lb ai/a

Time Apply in the fall after crop is dormant and before spring growth starts.

Remarks Consult label for the product used. Broadcast spray dormant alfalfa established 1 year or more. Use the 0.25-lb rate of Sencor if the only target weed is common chickweed.

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 (Solicam DF)

Rate 1 to 2 lb ai/a (1.27 to 2.58 lb/a Solicam DF)

Time Apply no earlier than 5 months after crop emerges, or to dormant alfalfa, or after a harvest in the growing crop 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 required to move herbicide into soil. Fall or winter applications are recommended in nonirrigated areas with less than 15 inches of annual moisture (rain and snow combined) or less than 4 inches of spring rain. Will not control established weeds. Control established weeds or weeds that emerge before activation with a labeled postemergence herbicide.

Caution Do not apply to seedling alfalfa earlier than 5 months after planting. Do not exceed 2 lb ai/a per year. Preharvest interval is 28 days. Note rotation restrictions. Bioassay soils containing more than 65% sand before crop rotation. Rotation crops can be planted when no signs of phytotoxicity are observed in bioassay plants for 4 months after emergence.

Site of action Group 12: bleaching; inhibits carotenoid biosynthesis

Chemical family Pyridazinone

paraquat (Gramoxone Inteon, Firestorm, Parazone)

Rate Firestorm: 0.49 to 1 lb ai/a (1.3 to 2.7 pints/a product). Gramoxone Inteon: 0.5 to 0.75 lb ai/a (2 to 3 pints/a product). Add nonionic surfactant with 75% or greater surface-active agent at 1 pint, or crop oil concentrate with 15% to 20% approved emulsifier at 1 gal/100 gal spray mix.

Time Apply after last fall cutting when crop is dormant and before spring growth starts.

Remarks Apply soon after weeds germinate. Alfalfa should be dormant. Do not apply if fall regrowth after the last cutting is more than 6 inches high or if spring regrowth is more than 2 inches high. Control decreases as weed size increases. Use 20 gal/a or more water carrier for ground application. Paraquat is a contact herbicide. Excellent knockdown plus residual control usually is obtained by combining paraquat with one of the residual herbicides.

Caution A restricted-use herbicide. Do not pasture animals in treated fields before first cutting. 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 H2O)

Rate 1 to 4 lb ai/a (1.2 to 4.8 quarts/a Prowl H2O)

Time Fall after the last cutting, during winter dormancy, in the spring, or between cuttings.

Remarks Controls most annual grasses and certain broadleaf weeds, including dodder, as they germinate. Apply to alfalfa that has gone through one growing season. May apply in a single application, or in sequential applications. Apply prior to the alfalfa reaching 6 inches in growth. Soil incorporation with rainfall or sprinkler will enhance activity.

Caution Do not harvest alfalfa hay or forage less than 14 days after applying up to 2 pints/a. If more than 2 pints/a are applied, do not harvest for hay or forage within 50 days of application. Utilize the 28 day harvest interval only once per cropping season. Do not exceed 4 quarts/a of product per year. Refer to label for crop rotation restrictions.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

saflufenacil (Sharpen)

Rate 0.022 to 0.045 lb ai/a (1 to 2 oz/a Sharpen)

Time Apply to dormant alfalfa at least 90 days before harvest to avoid yield reductions in the first cutting.

Remarks 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 2 oz/a per cropping season. Sharpen can cause leaf necrosis on alfalfa but new growth will be normal and usually yield is not reduced.

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

Chemical family Pyrimidindione

terbacil (Sinbar WDG)

Rate 0.4 to 1.2 lb ai/a (0.5 to 1.5 lbs/a Sinbar WDG)

Time Apply to dormant alfalfa after frost but before January 1.

Remarks Apply as a broadcast spray to dormant alfalfa established 1 year or more. Use lower rate on coarse, sandy soils or soils low in organic matter.

Caution Do not use on sand, loamy sand, or gravelly soil. Do not use on soils with less than 1% organic matter. Do not apply on snow-covered or frozen ground. Do not replant treated areas to any crop within 2 years after last application.

Site of action Group 5: photosystem II inhibitor

Chemical family Uracil

trifluralin (Treflan HF or Treflan TR-10)

Rate 2 lb ai/a

Time Apply before weeds emerge.

Remarks Trifluralin must be activated by a single rain or overhead sprinkler irrigation of at least 0.5 inch, or by furrow irrigation that thoroughly wets beds between furrows. If not activated within 3 days, mechanically incorporate trifluralin with equipment that won't damage alfalfa. May be applied during dormancy or during the growing season after a cutting. Apply before weed seeds germinate; trifluralin will not control established weeds. If downy brome and other winter annual grasses are targets, apply immediately after a cutting between August 1 and October 1.

Caution Do not cut for hay or graze within 21 days after application. Apply no more than 2 lb ai/a per growing season. Note recropping restrictions. In the year after application, plant only those crops for which trifluralin is registered as a preplant treatment, or crop may be injured.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline