New Plantings

2,4-D amine (many trade names)

Rate 0.24 to 1.43 lb ae/a (0.5 to 3 pints/a)

Time May be applied before or after planting. Apply when weeds are actively growing, preferably before bud stage on annual weeds and at bud stage for perennials. Repeat treatments may be required for less susceptible weeds. Some labels restrict use to one broadcast application per year.

Remarks Controls emerged broadleaf weeds. Glyphosate may be tank-mixed in preplant applications to broaden weed control. May be applied through wick applicators or conventional ground sprayers.

Caution Do not let 2,4-D contact leaves or green tree bark. Avoid drift. Do not apply within 2 days after an overhead sprinkler irrigation or rain, and do not irrigate for 3 days after treatment.

Site of action Group 4: synthetic auxin

Chemical family Phenoxy acetic acid

clopyralid (Transline and other trade names)

Rate 0.125 to 0.25 lb ae/a (0.33 to 0.66 pint/a)

Time Apply to new plantings only after they have several inches of new, healthy growth. Apply as a broadcast spray over the trees, or as a banded or directed spray.

Remarks Consult label for broadleaf weeds that clopyralid can control. Multiple applications may be made as long as total does not exceed 0.5 lb ae/a (1.33 pints/a).

Caution Avoid drift. Rain or irrigation within 6 to 8 hours of application may reduce efficacy. Carefully follow all rotation crop restrictions and other precautions.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

dimethenamid-P (Tower)

Rate 1 to 1.5 lb ai/a (21 to 32 fl oz/a)

Time Apply to new plantings only after they have been watered and the soil has been packed and settled well around the tree roots. Apply as a broadcast spray over the trees or as a banded or directed spray.

Remarks May be applied during site preparation and establishment. Make sure planting slit is well closed and herbicide does not contact tree roots. Apply prior to weed emergence.

Caution Do not apply during budbreak.

Site of action Group 15: inhibits cell growth and division

Chemical family Chloroacetamide

dimethenamid-P + pendimethalin (Freehand 1.75G)

Rate 1.75 to 3.5 lb ai/a (100 to 200 lb product/a)

Time Apply to new plantings only after they have been watered and the soil has been packed and settled well around the tree roots. Apply prior to weed emergence.

Remarks May be applied during planting and establishment. Make sure planting slit is well closed and herbicide does not contact tree roots. Rain or overhead irrigation is necessary to move the herbicide into soil.

Site of action Groups 15 and 3: inhibits cell growth and division and microtubule assembly inhibitor

Chemical family Chloroacetamide and dinitroaniline

diuron (Direx and other trade names)

Rate 0.8 to 2.4 lb ai/a. Use lower rates (0.8 to 1.6 lb ai/a) on coarse soils.

Time Apply before weeds emerge, or while they are small.

Remarks Labels may differ among products. Use lower rates on coarse soil. Rain or overhead irrigation is necessary to move the herbicide into soil. May apply prior to or after planting. If applying after planting, prevent treated soil from coming in contact with roots during the planting operation. If buds are beginning to swell, direct application, and use shields to keep spray off of buds and any green tissue. If weeds are present at time of treatment, add a surfactant at 1 to 2 quarts/100 gal of solution.

Caution Do not use on gravelly soils, or on any soil with less than 0.5% organic matter. Sprinkler irrigation might injure trees in coarse soils. Do not apply to stressed trees; injury may occur. Do not apply to frozen soils.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

flumioxazin (Redeagle, SureGuard)

Rate 0.25 to 0.38 lb ai/a (8 to 12 oz/a product)

Time Apply during site preparation prior to transplanting. For optimal weed control, apply before weed emergence or after a burndown herbicide has controlled existing vegetation.

Remarks Rain or overhead irrigation is necessary to move the herbicide into soil. Mechanical incorporation is not recommended.

Caution Transplant operations must take place at least 3 months after application.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family N-phenylphthalimide

glufosinate (Finale VU)

Rate 0.5 to 1.5 lb ai/a, depending on weed species and size.

Time Apply before planting, for site preparation.

Remarks May be used to control weeds before planting. Prepare ground early to allow maximum weed emergence. May include methylated seed oil (MSO) at 1% v/v or non-ionic surfactant (NIS) at 0.25% v/v spray solution. The addition of 8.5 to 17 pounds of ammonium sulfate (AMS) per 100 gal of water may result in better weed control.

Caution May plant as early as 12 hours after application.

Site of action Group 10: inhibits glutamine synthetase

Chemical family Phosphinic acid

glyphosate (many trade names)

Rate 1.5 to 3.75 lb ae/a, depending on weed species.

Time Apply before planting, for site preparation.

Remarks May be used to control weeds before planting. Prepare ground early to allow maximum weed emergence. Mix 1 quart or more nonionic surfactant per 100 gal of spray solution. Use surfactant with more than 50% ai. Surfactants with less than 50% ai require a higher surfactant volume per 100 gal of spray solution.

Caution Using this product without surfactant may reduce performance.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

metsulfuron methyl (Escort XP and other trade names)

Rate 0.3 to 1.2 oz ai/a (0.5 to 2 oz/a product)

Time Apply prior to planting or over the top after planting, before seedlings have broken dormancy (prior to bud break), and after soil has settled around the roots.

Remarks Rain or overhead irrigation is required to move herbicide into soil. Weed control is best when applying just prior to, or shortly after weed emergence.

Caution Do not apply after bud break. Surfactant is not recommended when applying over the tops of trees. When applying after planting, make sure adequate rainfall has occurred to close planting slit and close soil around the roots. Do not apply to trees under stress from low fertility, disease, insect damage, severe weather conditions, or water-saturated soils; tree injury or death may occur.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

oxyfluorfen (Goal, Galligan, and other trade names)

Rate 1 to 1.5 lb ai/a before bud break.

Time Apply after planting to dormant cottonwood cuttings.

Remarks Direct spray to base of cottonwood tree. For best control, apply before weeds emerge. Adding 1 quart/100 gal spray mix of nonionic surfactant enhances control of emerged weeds.

Caution Applications after bud break may injure crop.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Diphenylether

paraquat (Gramoxone, Firestorm)

Rate 0.5 to 1 lb ai/a

Time Apply before planting, for site preparation.

Remarks May be used to control weeds before planting. Prepare ground early to allow maximum weed emergence. Good spray coverage is essential for good weed control. Plant with minimal soil disturbance. Add 1 pint of nonionic surfactant or 2 pints of crop oil concentrate to 100 gal of spray mix. Apply in at least 20 gal/a spray volume.

Caution Paraquat is a restricted-use herbicide.

Site of action Group 22: photosystem I electron diversion

Chemical family Bipyridilium

pendimethalin (Pendulum Aquacap and other trade names)

Rate 2 to 4 lb ai/a

Time Apply after planting, before weed seed germinates.

Remarks Will not control established weeds. Apply after planting when soil around trees has settled. Rate applied determines the length of residual control.

Caution Do not let pendimethalin contact developing roots, because roots may be stunted.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

quizalofop P-ethyl (Assure II)

Rate 0.034 to 0.068 lb ai/a (5 to 10 fl oz/a)

Time Apply to annual or perennial grasses listed on label at optimum use rates based on weed size.

Remarks May be applied over poplars at planting, to aid in establishment. Always use either a nonionic surfactant at 1 quart/100 gal or a petroleum-based crop oil at 1 gal/100 gal.

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

Chemical family Aryloxyphenoxy propionate

saflufenacil (Detail)

Rate 0.022 to 0.13 lb ai/a (1 to 6 fl oz/a product)

Time Apply at least 2 months prior to planting trees.

Remarks Include methylated seed oil (MSO) at 1% spray volume. Does not control grass weeds. Rain or overhead irrigation is required to move herbicide into soil. Rate used will determine the length of residual control. Can be applied with glyphosate to improve speed of burndown and control of some glyphosate-tolerant species, such as horseweed.

Caution Observe buffer zones on label to avoid drift injury to sensitive crops and other vegetation.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Pyrimidinedione

terbacil (Sinbar, Sinbar WDG)

Rate 0.8 to 1.6 lb ai/a

Time Apply in late winter or early spring before weeds emerge, or while weeds are small. May apply before or after planting, but prior to bud swell. If applying after planting, allow soil to settle well around roots before application. May use only as a directed spray after bud swell.

Remarks Use lower rates on coarse soil. Rain or overhead irrigation is needed to move herbicide into soil. If weeds are present at time of treatment, add a surfactant at 1 to 2 quarts/100 gal of solution.

Caution Do not use on gravelly soils, or on any soil with less than 0.5% organic matter. Sprinkler irrigation might injure trees in coarse soils. Do not apply to frozen soils. If applying after bud swell, keep spray off of foliage, and apply as a directed spray only. Do not plant treated areas to any other crop for 2 years after last application.

Site of action Group 5: photosystem II inhibitor

Chemical family Uracil

trifluralin (Treflan HFP, Trust and other trade names)

Rate 0.5 to 1 lb ai/a

Time Apply before planting and thoroughly incorporate into top 2 to 3 inches of soil by cross-disking or rototilling.

Remarks Apply to trash-free and clod-free soil. Rate of application depends on soil type and organic matter. Incorporate into soil within 4 hours of application using equipment that ensures thorough soil mixing. Granular formulations may be activated with 0.5 inches rainfall or sprinkler irrigation without the need to mechanically incorporate. Will not control established weeds.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline