Broadleaf Weed Control
2,4-D amine, 2,4-D ester, 2,4-D choline (several trade names)
Rate 0.36 to 0.75 lb ae/A. Follow individual labels.
Time Eastern Oregon: apply after new grass has established five leaves in non-irrigated grass or two leaves in irrigated grass but before boot stage. Western Oregon: apply 2,4-D at 0.5 lb ae/A to fall-seeded stands after the two-leaf stage of grass growth. Established stands: apply spring or fall before boot stage. Idaho and Washington seedling grasses: apply 0.36 to 0.47 lb ae/A of most esters or amines after the five-leaf stage.
Remarks For use on newly established grass seed and established stands. Formulations vary widely in concentration and volatility. Amine and ester formulations are the traditional options, where ester formulations are slightly more active but have considerably higher volatility and risk for off-target vapor movement than amine formulations. Newer choline formulations have little to no volatility and risk for off-target vapor movement. Use choline or amine formulations near sensitive crops and during warmer temperatures. All formulations are susceptible to droplet drift, so use coarse droplets and other good spraying practices to prevent drift with all formulations.
Caution See individual labels for grazing restrictions. Do not allow drift. Do not use an oil carrier. If used with nitrogen fertilizer solutions, foliage may be damaged temporarily. Bentgrass seedlings should be well established before application. Grass seedling root development may be inhibited when 2,4-D is applied to early growth stages, so frequent irrigation when possible is important to help grasses establish.
Site of action Group 4: synthetic auxin
Chemical family Phenoxy acetic acid
carfentrazone (Aim EC)
Rate 0.008 to 0.031 lb ai/A (0.5 to 2 fl oz/A Aim EC)
Time Apply to emerged and actively growing weeds when weeds are small. May be applied before seeding and up to jointing stage of crop.
Remarks See label for specific tank-mixes and adjuvants to control problem weed species. Apply in at least 10 gal/A of spray solution. Good spray coverage is essential for control. Proper adjuvant use is critical for good activity, and addition of nitrogen to spray solution highly recommended where label permits.
Caution Do not exceed 0.093 lb ai/A of Aim EC per growing season.
Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor
Chemical family Triazinone
clopyralid (Stinger, several trade names)
Rate 0.094 to 0.25 lb ae/A (0.25 to 0.66 pint/A Stinger)
Time Apply in spring before boot stage and/or as a postharvest fall treatment. To control late-emerging Canada thistle, treat preharvest after grass seed is fully developed; apply to Canada thistle after most basal leaves emerge but before bud stage.
Remarks Re-treat as necessary, but do not exceed 0.66 pint/A Stinger per calendar year.
Caution Do not use on bentgrass unless injury can be tolerated. See label for rotation guidelines if land is taken out of grass seed production. Do not apply by air during an air temperature inversion. Some grass-seed straw export markets will not accept straw from grasses treated with clopyralid containing products.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
clopyralid + 2,4-D (Curtail)
Rate 0.095 to 0.19 lb ae/A clopyralid + 0.5 to 1 lb ae/A 2,4-D (2 to 4 pints/A Curtail)
Time Apply in spring before boot stage and/or as a postharvest fall treatment. To control late-emerging Canada thistle, treat preharvest after grass seed is fully developed; apply to Canada thistle after most basal leaves emerge but before bud stage.
Remarks Curtail contains 2,4-D amine, which may injure some grasses grown for seed. Injury potential varies greatly with geographic location and crop species and is influenced by application rate and timing. Consider your experience with 2,4-D to evaluate the risk of injury versus the benefits of weed control.
Caution For established grasses only. Risk of crop injury increases with increasing rate and later application. Do not use on bentgrass unless injury can be tolerated. Carefully follow label instructions on crop rotation if land is to be taken out of grass seed production. Do not apply by air during an air temperature inversion. Some grass-seed straw export markets will not accept straw from grasses treated with clopyralid containing products.
Site of action (both) Group 4: synthetic auxin
Chemical family (clopyralid) Pyridine; (2,4-D) Phenoxy acetic acid
clopyralid + MCPA (Curtail M)
Rate 0.092 to 0.184 lb ae/A clopyralid + 0.5 to 1 lb ae/A MCPA (1.75 to 3.5 pints/A Curtail M)
Time Apply in spring before boot stage and/or as a postharvest fall treatment. To control late-emerging Canada thistle, treat preharvest after grass seed is fully developed; apply to Canada thistle after most basal leaves emerge but before bud stage.
Remarks Curtail M contains MCPA ester, which may injure some grasses grown for seed. Injury potential varies greatly with geographic location and crop species and is influenced by application rate and timing. Consider your experience with MCPA to evaluate the risk of injury versus the benefits of weed control.
Caution For established grasses only. Potential for crop injury increases with increasing rate and later stages of application. Do not use on bentgrass unless injury can be tolerated. Carefully follow label instructions on crop rotation if land is to be taken out of grass seed production. Do not apply by air during an air temperature inversion. Some grass-seed straw export markets will not accept straw from grasses treated with clopyralid containing products.
Site of action (both) Group 4: synthetic auxin
Chemical family (clopyralid) Pyridine; (MCPA) Phenoxy acetic acid
dicamba (several trade names) + 2,4-D or MCPA or tribenuron methyl (several trade names)
Rate 0.25 to 1 lb ae/A dicamba + 0.5 to 1.5 lb ae/A 2,4-D or MCPA or 0.008 to 0.016 lb ai/A tribenuron
Time New seedlings: apply to new grass after it reaches three-leaf stage but before jointing. Do not exceed 0.5 lb ae/A dicamba. Established stands: apply before jointing stage. Apply when temperatures are 55°F to 75°F. Fall applications give better control of perennial, biennial, and winter annual broadleaf weeds after considerable foliage has developed. Do not exceed 1 lb ae/A dicamba.
Remarks Refer to individual product labels for specific rate, timing, and application directions. See specific remarks for tribenuron below.
Caution Use precautions to prevent drift. Some perennial ryegrass varieties are sensitive to tribenuron and may be injured. On newly established grass seed stands, combinations of dicamba + MCPA result in greater crop safety than dicamba + 2,4-D tank-mixes. See individual labels for grazing restrictions, but in general for 2,4-D, 7 days; for MCPA, 14 days (see labels); for dicamba, 7 days for up to 0.5 lb ae/A and 21 days if over 0.5 lb ae/A for lactating dairy cows (see labels). Do not apply after grass seed crop reaches jointing stage. Do not use more than 0.5 lb ae/A dicamba on bentgrass unless injury can be tolerated.
Site of action (dicamba, 2,4-D, and MCPA) Group 4: synthetic auxin; (tribenuron methyl) Group 2: acetolactate synthase (ALS) inhibitor
Chemical family (dicamba) Benzoic acid; (2,4-D and MCPA) Phenoxy acetic acid; (tribenuron methyl) Sulfonylurea
halosulfuron (Sandea, Motif)
Rate 0.031 to 0.062 lb ai/A (0.67 to 1.33 oz/A Sandea)
Time Apply in spring for postemergence control of yellow nutsedge and broadleaf weeds in established creeping bentgrass, Kentucky bluegrass, fine fescues, tall fescue and perennial ryegrass.
Remarks A sequential treatment may be necessary to control yellow nutsedge 6 to 10 weeks after the initial application. Always apply with a NIS at 0.5% v/v.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Pyrazole
MCPA amine, MCPA ester, + bromoxynil (Bronate Advanced, several trade names)
Rate 0.5 to 1 lb ae/A MCPA; 0.25 to 0.5 lb ai/A bromoxynil
Time Eastern Oregon: after new grass reaches three- to five-leaf stage. Western Oregon: apply MCPA at 0.5 lb ae/A on fall-seeded stands after two-leaf stage. Established stands: apply in fall or spring but before boot stage. Washington and Idaho seedling grasses: apply MCPA after grass tillers.
Remarks For newly established grass seed in eastern and western Oregon and established stands. Bromoxynil can be applied any time after grass emerges and before weeds are larger than listed on label (generally, four to six leaves).
Caution A 7-day waiting period is required after MCPA application before grazing. MCPA may injure bentgrass at higher application rates. Grass seedling root development may be inhibited when MCPA is applied to early growth stages; therefore, frequent irrigation is important to help grasses establish. Do not apply bromoxynil to cool-season grasses if air temperature is above 80°F, because crop injury may be unacceptable. Do not graze or feed straw from fields treated with bromoxynil.
Site of action (MCPA) Group 4: synthetic auxin; (bromoxynil) Group 6: photosystem II inhibitor
Chemical family (MCPA) Phenoxy acetic acid; (bromoxynil) Nitrile
saflufenacil (Sharpen)
Rate 0.022 to 0.045 lb ai/A (1 to 2 fl oz/A Sharpen)
Time Cool-season grasses: Apply to new grass seedings after the first tiller is fully established in the fall or spring. Apply anytime to established grasses in fall or spring after greenup until boot stage.
Remarks A methylated seed oil is required for optimum efficacy. Where allowed, addition of a nitrogen fertilizer such as ammonium sulfate also improves activity. See label for more information on adjuvants and tank-mixes.
Caution Do not exceed 4 or 6 fl oz/A per year on seedling or established grass seed stands, respectively. Sequential applications must be separated by at least 14 days; do not apply more than 2.0 fl oz/A per application. Sharpen may cause transitory injury to cool-season grasses under certain conditions, but new growth is normal and vigor is not reduced. The preharvest interval for seed is 50 days after application. There are no feeding or grazing restrictions.
Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor
Chemical family Pyrimidinedione
tribenuron methyl (several trade names)
Rate 0.008 to 0.016 lb ai/A
Time Fall or spring, when broadleaf weeds are actively growing.
Remarks May be used on seedling or established stands of perennial ryegrass, tall fescue, annual ryegrass, bluegrass, bentgrass, fine fescue, and orchardgrass. Use only the 0.008 lb ai/A rate on tall fescue and perennial ryegrass. Spring applications on tall fescue must be before stems start elongating. Use the 0.016 lb ai/A rate on established annual ryegrass, bluegrass, bentgrass, fine fescue, and orchardgrass. Always use a nonionic surfactant at 1 quart/100 gal. Adding 2,4-D at 0.25 to 0.5 lb ae/A plus liquid nitrogen fertilizer at 4 gal/100 gal aids weed control and crop safety.
Caution Some perennial ryegrass varieties are sensitive to tribenuron and may be injured. Do not apply to grass that is under stress. Do not feed or graze treated grass seed for 60 days after applying.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Sulfonylurea