Grass Seed Crops

Note Weed control in established perennial grass seed fields depends on effective management of crop residues. If grass seed fields cannot be burned after harvest, the recommended preemergence herbicide treatments may be less effective in controlling weeds. In unburned fields, remove crop residues by baling straw, or spreading straw as evenly as possible by mechanical means. Unburned grasses with considerable top re-growth may be damaged by fall-applied treatments made before October 15.

GRASS SEED—Seedbed Preparation

carfentrazone (Aim EC)

Rate Up to 0.031 lb ai/A (0.5 to 2 fl oz/A Aim EC)

Time Before planting or up to 24 hours after planting. Apply to actively growing weeds up to 4 inches tall and to rosettes less than 3 inches across.

Remarks See label for specific tank-mixes and adjuvant recommendations. Good spray coverage is essential for control.

Caution Do not exceed 0.093 lb ai/A of Aim EC per growing season.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Triazinone

carfentrazone + 2,4-D (Rage D-Tech)

Rate 0.008 to 0.033 lb ai/A carfentrazone and 0.37 to 1.48 lb ae/A 2,4-D (8 to 32 fl oz/A Rage D-Tech)

Time Apply up to 21 days before planting, and when broadleaf weeds are less than 6 inches tall.

Remarks The use of a nonionic surfactant, crop oil concentrate, or methylated seed oil is required. A high-quality sprayable liquid nitrogen fertilizer may be used at 2% to 4% v/v or AMS at 2 to 4 lb/A, in addition to the nonionic surfactant, COC, or MSO.

Caution Do not exceed 91 fl oz/A Rage D-Tech per year. Do not apply Rage D-Tech on light sandy soils, or soils containing less than 1% organic matter. See label for planting restrictions.

Site of action (carfentrazone) Group 14: protoporphyrinogen oxidase inhibitor, (2,4-D) Group 4: synthetic auxin

Chemical family (carfentrazone) triazinone, (2,4-D) phenoxy acetic acid.

glyphosate (several trade names)

Rate 0.5 to 3.75 lb ae/A

Time Apply to actively growing weeds.

Remarks Use higher application rates if weeds are over 6 inches tall. Apply 1.5 to 3.75 lb ae/A for perennial weed control. Delay tillage 3 days after treating annual weeds, at least 7 days after treating perennials. Refer to specific product label for direction on adding surfactants and for plant-back restrictions for grass seed crops.

Caution Do not graze or use feed from treated areas for 8 weeks after application.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

paraquat (several trade names)

Rate 0.5 to 1 lb ai/A

Time Apply from late November to December, in preparation for planting grasses in the spring. Seed between February 15 and March 15 on non-irrigated land.

Remarks Use 1 to 2 pints of nonionic surfactant or 1 gallon of crop oil concentrate per 100 gal spray mixture. If weather prevents treating in December, applications may be made into January (two applications may be needed for large weeds). If more weeds germinate after December treatments, paraquat may be applied up to the time the crop emerges if seed is well covered by soil. Apply to weeds in the three- to five-leaf stage.

Caution A restricted-use herbicide. Treatment controls only seedling weeds. Cultivate fields up to October 15 to mechanically control established weeds. Do not graze treated areas for livestock feed. Do not use straw from treated areas for animal bedding or feed. Use 2,4-D, dicamba, or bromoxynil for weed control later in the crop year.

Site of action Group 22: photosystem I electron diversion

Chemical family Bipyridilium

pyraflufen (several trade names)

Rate 0.0008 to 0.0032 lb ai/A

Time Apply to seedling weeds that are less than 4 inches tall or less than 3 inches in diameter if in the rosette stage 30 days before planting grass seed crops. The higher rate will be needed for difficult-to-control species such as kochia or field bindweed.

Remarks May be tank mixed with synthetic auxin herbicides and glyphosate to broaden the weed control spectrum. Always apply with a crop oil concentrate or nonionic surfactant for optimum activity.

Caution Do not exceed three applications or 5.5 oz/A of product during the preplant burndown period. Separate applications by 30 days. Do not graze treated areas.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Phenylpyrazole

GRASS SEED—Activated Carbon Band Planting System

activated carbon

Oregon and Washington only

Rate 25 lb/A in a 1-inch band (equal to a 300-lb/A broadcast application)

Time At planting.

Remarks Apply to smooth, crop residue-free seedbeds. A spray unit on a 12-inch drill applying a slurry band 1 inch wide directly over the seeded row works well. Use proper agitation to keep the carbon in suspension. Mix activated carbon with water at 0.5 lb/gal. Follow carbon application with diuron application (see entry immediately below).

diuron (several trade names)

Oregon and Washington only

Rate 2 to 2.4 lb ai/A (2.5 to 3 lb/A of an 80DF formulation)

Time Apply after planting but before rain or irrigation.

Remarks Oregon and Washington registrations. Not registered in Idaho. Broadcast immediately after planting and banding with activated carbon. Use lower rate in sandy soils. At least 1 inch of moisture is required within 2 weeks after applying diuron to activate herbicide and move it into the soil profile. Diuron is not strongly photodegraded, but losses can be significant if diuron remains on the soil surface for several weeks without significant moisture during hot and dry planting conditions.

Caution Do not use this system in grass seed rotations that will be replanted to any crop within 2 years because these rotational crops may be injured. Diuron will not control volunteer winter cereals, wild oat, or downy brome.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

GRASS SEED—Fall, Carbon-Seeded Perennial Ryegrass, Tall Fescue, and Orchardgrass

pronamide (Kerb SC)

Oregon only

Rate 0.125 to 0.25 lb ai/A (5.0 to 10.0 oz/A Kerb SC)

Time Apply in a tank-mix with a reduced rate of diuron after the carbon band seeding operation. Application must be made before the seeded crop emerges, and before rain dissipates the carbon band.

Remarks Apply only to fields with well-prepared, firmly packed seedbeds. An adequate carbon band that will absorb the applied herbicide must be present at time of treatment.

Caution A restricted-use herbicide. Do not apply pronamide to sandy or gravely areas in the field. Grower assumes all risks of crop injury or stand loss under unforeseen, adverse environmental conditions, if seedbeds are poorly prepared, or if carbon bands are inadequate at treatment. Do not graze treated fields within 180 days of application; see label for other restrictions and precautions.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Benzamide

GRASS SEED—New and Established Crops

Broadleaf Weed Control

2,4-D amine, 2,4-D ester (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. 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.

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.

Caution Do not exceed 0.093 lb ai/A of Aim EC per growing season.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Triazinone

carfentrazone + 2,4-D (Rage D-Tech)

Rate 0.008 to 0.033 lb ai/A carfentrazone and 0.37 to 1.48 lb ae/A 2,4-D (8 to 32 fl oz/A Rage D-Tech)

Time Apply from 5-leaf stage to boot stage in new plantings and up to the boot stage in established plantings, and when weeds are up to 4 to 6 inches tall.

Remarks A nonionic surfactant or crop oil concentrate is required. See label for more information on adjuvants and tank-mixes.

Caution Do not exceed 91oz/A Rage D-Tech or three applications per year. Tank-mixes with EC or ester formulations of other herbicides may increase leaf speckling. Do not apply to foliage wet from dew, rain, or irrigation, because increased crop injury may occur.

Site of action (carfentrazone) Group 14: protoporphyrinogen oxidase inhibitor; (2,4-D) Group 4: synthetic auxin

Chemical family (carfentrazone) triazinone; (2,4-D) phenoxy acetic acid

clopyralid (Stinger)

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 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

MCPA amine, MCPA ester, or bromoxynil (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

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 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

Bedstraw and Canada Thistle Management

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 when they are small. May be applied before seeding and up to jointing stage of crop.

Remarks See label for specific tank-mixes and adjuvant recommendations. Apply in at least 10 gal/A of spray solution. Good spray coverage is essential for control.

Caution Do not exceed 0.093 lb ai/A of Aim per growing season.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Triazinone

fluroxypyr (Starane Ultra)

Rate 0.11 to 0.14 lb ai/A fluroxypyr (0.3 to 0.4 pint/A Starane Ultra)

Time For best performance, apply to emerged and actively growing broadleaf weeds less than 4 to 8 inches in height. Only weeds that have emerged at time of application will be controlled. Apply to two-leaf seedling grasses up to early boot stage, or to established grasses before early boot stage.

Remarks Do not exceed 0.7 pints/A per growing season or 2 applications per season, and separate applications by 14 days.

Caution There are no grazing restrictions after applying Starane Ultra. Do not harvest grass for hay or silage from treated area within 7 days of application. Withdraw meat animals from treated forage at least 2 days before slaughter.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

fluroxypyr + bromoxynil (Starane NXT)

Rate 0.063 to 0.125 lb ai/A fluroxypyr + 0.26 to 0.5 lb ai/A bromoxynil (14 to 27.4 oz/A Starane NXT)

Time For best performance, apply to emerged and actively growing broadleaf weeds less than 2 inches high or 1 inch wide. Apply to two-leaf seedling grasses up to early boot stage or to established grasses before early boot stage. Reduced weed control may occur when applied in cold conditions. See label for recommended environmental conditions for timing of application.Remarks Seedling grasses tolerant to Starane NXT include Kentucky bluegrass, fescue, orchardgrass, and perennial ryegrass. Established grasses tolerant to Starane NXT include bluegrass, fescue, perennial ryegrass, and bermudagrass.

Caution Do not plant any nonlabeled rotation crop within 120 days of application. Do not feed treated grasses to livestock or allow treated area to be grazed.

Site of action (fluroxypyr) Group 4: synthetic auxin; (bromoxynil) Group 6: photosystem II inhibitor

Chemical family (fluroxypyr) pyridine; (bromoxynil) nitrile

fluroxypyr + clopyralid (WideMatch)

Rate 0.094 to 0.125 lb ai/A fluroxypyr + 0.094 to 0.125 lb ai/A clopyralid (1 to 1.33 pints/A WideMatch)

Time For best performance, apply to emerged and actively growing broadleaf weeds less than 4 inches tall or before vining. Apply to two-leaf seedling grasses up to early boot stage or to established grasses before early boot stage. Weed control may be reduced when applied in cold conditions. See label for recommended environmental conditions at application.

Remarks Controls broadleaf weeds including kochia, wild buckwheat, Canada thistle, volunteer potato, and prickly lettuce. Tank-mix compatible with MCPA, dicamba, bromoxynil, or 2,4-D. Tank-mixes help to broaden annual-weed control spectrum but may reduce efficacy on perennial weeds such as Canada thistle. Do not tank mix with 2,4-D, MCPA, or dicamba unless the risk of crop injury is acceptable.

Caution Do not apply to bentgrass unless crop injury can be tolerated. See label for rotation restrictions on other crops. Do not harvest grass for hay or silage from treated area within 7 days of application. Withdraw meat animals from treated forage at least 2 days before slaughter. Some grass-seed straw export markets will not accept straw from grasses treated with products containing clopyralid.

Site of action (both) Group 4: synthetic auxin

Chemical family (both) pyridine

Field Bindweed Management

quinclorac (Paramount)

Rate 0.248 to 0.375 lb ai/A (5.3 to 8 oz/A Paramount)

Time Apply in fall after harvest but before a killing frost. Field bindweed should be actively growing and at least 4 inches long.

Remarks May be used on Kentucky bluegrass, annual and perennial ryegrass, and fine and tall fescue seed fields. Adequate soil moisture and/or light rain after application is required for root uptake. Repeat applications are necessary to maintain adequate control. Adding methylated seed oil or crop oil concentrate is required for consistent control. Nitrogen solutions or ammonium sulfate can be added to enhance control but should not replace the MSO or COC.

Caution Do not graze treated fields. Do not feed treated grasses, forage, hay, silage, straw, seed, or seed screenings to livestock. Do not apply by air west of the Cascades or in Spokane County, WA.

Site of action Group 4: synthetic auxin

Chemical family Quinoline carboxylic acid

Annual Bluegrass Management

glufosinate-ammonium (Rely 280 or Reckon 280SL)

Oregon only, grass weeds

Rate Fall broadcast: use 0.18 lb ai/A (10 oz/A Rely 280 or Reckon 280); Spring broadcast: use 0.30 to 0.37 lb ai/A (16.5-20 oz/A Rely 280 or Reckon 280); Spring directed, shielded spray: use 1.0 to 1.5 lb ai/A (55-82 oz/A Rely 280 or Reckon 280)

Time Apply to established and seedling fields. Treat newly established fields after the first tiller has developed and prior to December 1. Spray established fields when crop begins active growth in early spring, usually prior to April 1.

Remarks One spring broadcast application can be made following a fall broadcast application. Use in the spring as a rescue treatment in established crops or if fall-applied herbicide programs have not been adequate. Glufosinate controls or suppresses annual and roughstalk bluegrass, mannagrass, and some brome species.

Caution Glufosinate may severely injure some crop species. Do not broadcast apply glufosinate on fine fescue, orchardgrass, or Poa spp. grown for seed. Directed, shielded sprays are suggested for fine fescues, orchardgrass or Poa spp. grown for seed. See specific restrictions and directions on the Rely 280 SLN OR-100012 label or Reckon 280 SLN OR-120017 label. Consult a crop adviser or an OSU Extension specialist for more information. Growers assume all liability for crop injury when using glufosinate in grasses grown for seed. Do not graze treated fields for one year following application.

Site of action Group 10: glutamine synthase inhibitor

Chemical family Phosphinic acid

GRASS SEED—Established Crops

Special-equipment Applications

Wick, wiper, or roller applications

glyphosate (several trade names)

Rate 3 lb ae glyphosate (1 gal of 3 lb ae/gal formulation) + 2 gal water

Time Weeds should be at least 6 inches taller than the crop. For best results, perennial weeds should be in early-bud, late-boot, full-bloom, or early-seed stage. Control annual weeds before hard seed stage.

Remarks Use in wick or wiper applicators to control annual and perennial weeds. In heavy infestations, reduce speed to ensure adequate wiper coverage. Two cross-direction applications may improve control. Repeat applications may be required to control dense clumps or severe weed infestations. In roller applicators, a more dilute rate of 3 lb ae glyphosate (1 gal) + 5 gal water has proven satisfactory.

Caution Equipment should be in good condition to avoid dripping or crop contact. Maintain roller speed at 40 to 60 rpm; do not exceed 5 mph. Do not graze or feed within 14 days of wiper application.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

Shielded sprayer applications

glyphosate (several trade names)

Rate Apply 0.75 to 2.25 lb ae (1 to 3 quarts of 3 lb ae formulation) as a broadcast spray in 10 to 20 gal/A total spray volume

Time Apply to actively growing weeds.

Remarks Results are best when grass is planted in uniform, straight rows and crop is small enough to easily pass alongside or through the protective shields.

Caution Grower assumes all responsibility for crop losses from misapplication.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted