Birdsfoot Trefoil

Tim Prather
March 2022

2,4-DB (Butyrac 200 or Butoxone 200)

Rate 0.5 lb ae/A to 1.5 lb ae/A (1 to 3 quarts/A Butyrac 200 or Butoxone 200)

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

benefin (Balan DF)

Rate 1.2 to 1.5 lb ai/A (2 to 2.5 lb/A Balan DF)

Time Apply up to 10 weeks preplant. Do not apply after seeding.

Remarks For preemergent control of annual grasses and broad-leaf weeds in new plantings. Use 2 lb/A Balan DF on coarse to medium soils and up to 2.5 lb/A Balan DF on fine textured 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 months after application. Wait 12 months before seeding corn, oats, red beets, root crops, or spinach.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

carfentrazone (Aim EC)

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

Time Apply Aim EC in the fall after the crop is dormant or in the spring before spring growth starts.

Remarks Apply as a broadcast spray to dormant trefoil that has been established for at least 1 year. See label for tank mixes. Use rates up to 2.5 oz/A in 10 gal of water for optimal control. Always add an adjuvant. See Aim EC label for recommended additives.

Caution Do not harvest stands grown for seed for 3 days after application. Do not apply more than 2.5 oz of Aim EC per year.

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

Chemical family Triazolinone

clethodim (Select 2EC, Select Max, Intensity One, Section Three)

Rate Select 2EC, or Intensity: use 0.094 to 0.25 lb ai/A (6 to 16 fl oz/A product). Section Three: use 0.094 to 0.24 lb ai/A (4 to 10.5 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 hour after application. Do not apply within 15 days of grazing, feeding, or harvesting for forage or hay. Do not exceed 32 fl oz/A of Select 2EC or 64 fl oz/A of Select Max or 21.3 fl oz/A Section Three.

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

Chemical family Cyclohexanedione

diuron (Karmex, Direx 4L or others)

Western Oregon only

Rate 1.6 lb ai/A (1.6 quarts/A product)

Time Apply after trefoil is dormant, in late October to early December.

Remarks Controls annual grasses and broadleaf weeds in established trefoil. Use mechanical agitation.

Caution Apply only on stands that are at least 1 year old. Diuron is a soil sterilant at high rates, so take care to avoid double applications. Do not apply to sand, loamy sand and gravelly soils nor when organic matter is less than 1%. Do not apply to frozen ground.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

EPTC (Eptam 7E)

Rate 2 to 3.9 lb ai/A (2.25 to 4.5 pints/A Eptam 7E)

Time Prior to planting, 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 in 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

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 50-W)

Rate 0.5 to 2.0 lb ai/A (1 to 4 lb/A 50-W; )

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. Do not apply to frozen soil.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Benzamide

sethoxydim (Poast Plus)

Rate 0.28 to 0.47 lb ai/A (1.5 to 3.75 pints/A Poast Plus)

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. Do not apply more than 9.75 pints per season.

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

Chemical family Cyclohexanedione