Orchard Crops
Apples and pears; apricots, peaches, nectarines, cherries, prunes, and plums; hazelnuts, walnuts, and chestnuts
Ed Peachey
Revised November 12, 2008

ORCHARD CROPS—Site Preparation
•  glyphosate (numerous product names)
Rate  Read label carefully for crops listed and geographic location
Time  Apply lower rates for actively growing annual weeds.
Remarks  Consult label for higher rates and application time for perennial weeds. Additional surfactant or ammonium sulfate fertilizer sometimes improves control when weeds are growing slowly. Inhibits production of three amino acids and protein synthesis.
Caution  If repeat treatments are necessary, do not exceed 10.6 lb ai/A (10.6 quarts) in 1 yr. Grazing is prohibited. Repeated use of glyphosate has caused resistant biotypes to develop in some cropping systems.
Herbicide resistance management  Repeated use of glyphosate in at least one orchard in western Oregon has selected for a resistant biotype of annual ryegrass. Overreliance on herbicides with a single site of action for orchard floor maintenance increases the risk of selecting for resistance in other weed species, and it threatens the long-term usefulness of glyphosate for weed control in orchards and other crops. Several alternative, nonselective herbicides, listed below, have different sites of action and can be applied in rotation with glyphosate to reduce the risk of selecting for weeds that are resistant to glyphosate. Refer to “Managing Herbicide-resistant Weeds” and “Agrichemicals and their Properties” in this handbook for more information.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
ORCHARD CROPS—New Plantings, Nonbearing
•  geo-textiles 
available at agriculture and garden supply stores
Remarks  Spunbonded fabrics (nonwoven): lightweight, extruded polypropylene fibers; require mulch cover due to moderate UV light sensitivity; weed roots and rhizomes can penetrate fabric unless removed before establishment; cheapest option.
Woven fabrics: moderate-weight polypropylene fibers woven into a mat; can be used without mulch cover due to UV light stability; weed roots and rhizomes can penetrate fabric, although tightness of weave can prevent some weeds; moderate cost.
Laminates: highly porous, dense poly film bonded to capillary fibers with a pressed, nonwoven bottom layer. The slick surface wets and dries rapidly, which prevents weed establishment except for perennial rhizomes which can penetrate the laminate; most expensive geo-fabric.
•  napropamide (Devrinol)
all except chestnuts
Rate  5 lb ai/A (50 lb/A Devrinol 10-G)
Time  Apply immediately after transplanting to firmed soil before weeds emerge. Between November and February, activate with rain or overhead irrigation within 2 wk; the rest of the year, activate within 24 hours.
Remarks  Where convenient, shallow mechanical incorporation appears to improve activation. Inhibits root growth.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Acetamide
•  oryzalin (Surflan)
Rate  2 to 6 lb ai/A (2 to 6 quarts/A Surflan AS)
Time  Apply late fall to early spring to firmed soil; activate with rain or overhead irrigation or with shallow cultivation.
Remarks  Not suggested for soils with more than 5% organic matter. Use higher rates for longer residual weed control. Avoid exposing transplant roots to treated soil. Inhibits cell division or mitosis, primarily in roots.
Caution  Do not apply beneath newly planted trees until soil has settled and there are no cracks.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  trifluralin (Treflan 4EC)
newly established; except pears, apples, cherries, and hazelnuts
Rate  0.5 to 1 lb ai/A (1 to 2 pints/A Treflan 4EC)
Time  Apply preplant and incorporate immediately by cross-disking or rototilling.
Remarks  If crops are planted between trees, follow directions for both crops. Inhibits mitosis in roots and shoots. Preharvest interval is 60 days.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  isoxaben (Gallery or Gallery T&V)
nonbearing crops, except chestnuts
Rate  0.495 to 0.998 lb ai/A (0.66 to 1.33 lb/A product)
Time  Apply late summer to early fall, in early spring, or immediately after cultivation to debris-free soil surface. Activate with 0.5 inch water or shallow cultivation before weeds begin to emerge.
Remarks  Identify weeds and adjust rates according to charts listed on label. Chemical stability remains adequate when left on soil surface for 21 days.
Caution  Do not apply to newly transplanted crops until the soil has settled and cracks disappear. 
Site of action  Group 21: inhibits cell wall synthesis Site B 
Chemical family  Benzamide
•  isoxaben + trifluralin (Snapshot 2.5TG)
nonbearing crops, except chestnuts
Rate  5 lb ai/A (200 lb/A Snapshot 2.5TG)
Time  Apply to weed- and debris-free soil that has settled with water and is free of cracks after transplanting.
Remarks  Activate within 21 days using 0.5 inch of water or shallow cultivation before weeds begin to emerge.
Caution  Follow label instructions for repeat treatments.
Site of action  (isoxaben) Group 21: inhibits cell wall synthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor
Chemical family  (isoxaben) benzamide; (trifluralin) dinitroaniline
•  trifluralin + isoxaben + oxyfluorfen (Showcase) 
nonbearing crops only, including  apricots, cherries, nectarines, peaches, plums, and prunes; excluding apples, pears, hazelnuts, walnuts, and chestnuts
Rate  2.5 to 5 lb ai/A (100 to 200 lb/A Showcase)
Time  Apply to nonbearing fruit and nut trees that will not bear fruit for at least 1 yr.
Remarks  Apply evenly with drop or rotary type spreader to avoid crop injury. Apply to weed-free soil. Controls many weeds that grow from seeds but will not control weeds that emerge from stolons, rhizomes, or root pieces. Control existing weeds with cultivation or postemergence herbicides. Activate within 3 days using 0.5 inch of water before weeds begin to emerge. See label for repeat treatments. 
Caution  To avoid injuring crop, do not apply to newly transplanted trees until packing and irrigation or rain have settled soil and no cracks appear. Repeat applications of 150 lb/A or more should not be made within 60 days of a previous application. Do not apply when wind favors drift of granule from the target area.
Site of action  (trifluralin) Group 3: microtubule assembly inhibitor; (isoxaben) Group 21: inhibits cell wall synthesis Site B; (oxyfluorfen) Group 14: inhibits protoporphyrinogen oxidase
Chemical family  (trifluralin) dinitroaniline; (isoxaben) benzamide; (oxyfluorfen) diphenylether
•  pronamide (Kerb)
nonbearing fruit trees
Rate  1 to 4 lb ai/A (2 to 8 lb/A); rate depends on species present and soil texture.
Time  Apply in fall after fruit is harvested. 
Remarks  Apply to established blueberries. Results are optimum if soil is below 55°F and if followed by rain or irrigation. Requires moisture from overhead irrigation or rain to activate. Inhibits root growth. Poor control of weeds of the Asteraceae (Composite) family.
Caution  A restricted-use herbicide. Do not exceed 8 lb/A or one application per year.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Benzamide
•  fluazifop (Fusilade DX)
Rate  0.25 to 0.375 lb ai/A (16 to 24 oz/A Fusilade DX). Refer to specific grassy weeds on label.
Time  Apply to actively growing grasses or within 7 days after irrigation as a directed spray with 1% crop oil or 0.25% nonionic surfactant. 
Remarks  Identify grasses and adjust rates depending on susceptibility and stage of weed growth as label instructs. Results often are erratic on grasses stressed by lack of vigor, drought, high temperature, or low fertility. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescues resist treatment. Inhibits fatty acid production, cell membranes, and new growth.
Caution  Do not exceed 72 fl oz/A per season. Grazing is prohibited. 
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  sethoxydim (Poast)
Rate  0.28 to 0.47 lb ai/A (1.5 to 2.5 pints/A product)
Time  Identify susceptible grasses and apply at optimum growth stage listed on the label.
Remarks  Apply 2 pints/A of a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, high heat, or low fertility. Resistant grasses include annual bluegrass and all fine fescues; quackgrass can be suppressed. Inhibits fatty acid production, cell membranes, and new growth.
Caution  Preharvest intervals are 14 days for apple and pear; 25 days for apricot, cherry (sweet and sour), nectarine, and peach; 15 days for nuts; and 1 yr for plums. Note maximum annual amounts per acre listed on label. 
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  clethodim (Envoy, Prism, or Select)
nonbearing trees only
Rate  0.06 to 0.125 lb ai/A (6 to 8 oz/A Select)
Time  Apply postemergence to actively growing annual or perennial grasses as listed on label.
Remarks  Consider environmental and plant growth conditions that affect leaf uptake (see label for guidelines).
Caution  Do not exceed 68 fl oz/A per season. Do not apply directly over the top of fruit or nut crops that may be used for rootstock, or crops may be injured.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor 
Chemical family  Cyclohexanedione
•  paraquat (Gramoxone Inteon)
Rate  0.625 to 1 lb ai/A (2.5 to 4 pints/A Gramoxone)
Time  Apply in 30 to 150 gal/A of water as a directed spray.
Remarks  Add a nonionic surfactant or crop oil concentrate according to label specifications, taking care to avoid anionic formulations that react in the tank to form insoluble precipitates. Acts as a contact; absorbs energy produced by photosynthesis, forming peroxides that disrupt living cells.
Caution  A restricted-use pesticide. Do not ingest or inhale spray mist. Wear protective face shields, respirators, and clothing. Do not apply if nuts are on ground. Grazing prohibited.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  glyphosate (numerous product names)
Rate  Read label carefully  for crops listed and geographic location
Time  Apply to actively growing weeds.
Remarks  Additional surfactant or ammonium sulfate according to label instructions may improve control of slightly stressed weeds. Adjust concentration depending on equipment, or consult label about rate and time of application, especially for perennial weeds. Select application equipment to prevent crop injury by directing spray or by using selective applicators.
Caution  Do not let spray or mist contact foliage, green bark, suckers, or other parts of trees. Contact with other than natural brown bark can seriously damage crop. Grazing is prohibited. Inhibits production of three amino acids and protein synthesis.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glyphosate (several products)
Rate  Wiper: 33% solution
Time  Apply 1 gal product with 2 gal water and wipe weeds, avoiding contact with desirable vegetation.
Remarks  In severe infestations, reduce equipment ground speed or apply in two directions to ensure contact with wiper. (See remarks above.)
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glufosinate ammonium (Rely)
apples, hazelnuts, and walnuts
Rate  0.75 to 1.5 lb ai/A (3 to 6 quarts/A Rely)
Time  Apply to actively growing weeds as a directed spray or spot treatment according to stage of weed growth.
Remarks  Avoid drift to or treatment of desirable foliage or green bark during establishment year.
Caution  Do not exceed 4.5 lb ai/A per 12-mo season. Do not graze or apply within 14 days of harvest.
Site of action  Group 10: inhibits glutamine synthetase
Chemical family  Phosphinic acid
•  oxyfluorfen (Goal 2XL)
Rate  1.25 to 2 lb ai/A (5 to 8 pints/A Goal 2XL)
Remarks  Controls broadleaf weeds pre- and postemergence depending on application rate and weed species.
Time  Apply only to healthy trees. Direct spray toward the base of trees, avoiding direct plant contact. Acts as contact, either directly on broadleaf weeds or at soil surface as weeds emerge.
Site of action  Group 14: inhibits protoporphyrinogen oxidase
Chemical family  Diphenylether
•  sawdust
hazelnuts and other crops
Rate  2 large scoops per 2 sq ft
Time  Apply 3- to 4-inch layer of mulch immediately after planting to suppress weed germination and conserve soil moisture.
Remarks  Avoid mounding or thickly layering near tree trunk to reduce crown rot and injury from mice and other vertebrate pests. Lower rates of registered herbicides for new plantings sometimes can enhance weed control if applied before spreading mulch.
ORCHARD CROPS—Established Plantings—Applications that Persist in the Soil
•  pendimethalin (Prowl H2O)
bearing fruits and nuts (H2O formulation); 3.3EC formulation for nonbearing only
Rate  Prowl H2O—1.9 to 3.8 lb ai/A (2 to 4 quarts/A), depending on desired length of weed control. Prowl 3.3 EC—1.98 to 3.96 lb ai/A (2.4 to 4.8 quarts/A)
Time  Apply before weed emergence.
Remarks  May be surface applied preemergence or surface incorporated. Prowl is most effective if incorporated into soil with rain, irrigation, or shallow mechanical incorporation. Apply in single application or sequentially with an interval of 30 days or more. Do not exceed 4 quarts/A per year. Do not feed forage or graze livestock in treated orchards. Preharvest interval is 60 days. 
Caution  Do not apply over tops of trees with leaves, bud, or fruit. Apply directly to the ground beneath the trees or areas between rows. 
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  flumioxazin (Chateau WDG)
stone and pome fruits (in select counties west of the Cascades in Oregon and Washington, not Idaho), and nuts
Rate  0.188 to 0.38 lb ai/A (6 to 12 oz/A Chateau WDG). Refer to organic matter, soil types, and rates listed on label for various broadleaf weeds. 
Time  Before weeds emerge. Preferred timing is in fall when rain will activate the herbicide.
Remarks  Apply to a weed-free surface. Chateau has limited postemergence activity that is enhanced by adding surfactants. Add 0.25 %v/v nonionic surfactant or 1% crop oil concentrate to enhance postemergence burndown activity. Tank-mix with herbicides such as glyphosate, glufosinate, or paraquat to kill large weeds. Residual weed control will be reduced if vegetation prevents the spray from reaching the soil. Moisture is necessary to activate the herbicide for residual weed control. Dry weather after application may reduce effectiveness. Do not exceed 12 oz/A product per application or 24 oz/A per year. Use the 6-oz/A rate if soil has significant sand or gravel.
Caution  Preharvest interval is 60 days. Do not apply to soils that are susceptible to dispersal by wind. This herbicide can move to susceptible crops on soil particles and cause damage. Do not apply within 300 yd of nondormant pears. Do not mow treated areas between budbreak and final harvest. Dust created by mowing may injure susceptible plants. Avoid direct or indirect spray contact with foliage or green bark. Do not apply to trees established less than 1 yr.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Diphenylether
•  pendimethalin (Prowl or Pendulum)
nonbearing crop only
Rate  2.4 to 4.8 quarts/A of Prowl (2 to 4 lb ai/A) 
Time  Apply to newly planted grapes and 1-yr-old vines before buds swell and after ground settles around vines and cracks are gone. Application after bud swell may cause leaf distortion.
Remarks  Spray directly on the ground beneath newly planted and 1-yr-old vines. Overhead watering or rain is required (usually 0.5 inch is adequate) within 7 days for herbicide activation. Can also be applied before transplanting vines by incorporating into the top 2 inches of soil or by applying to soil surface. Minimize contact of treated soil with the vine roots when transplanting.
Caution  Do not apply over the tops of vines with leaves or open buds. Do not graze treated areas or exceed 6.3 quarts/A per year.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  dichlobenil (Casoron CS)
apples, pears, cherries, and hazelnuts only; bearing and nonbearing
Rate  1.96 to 3.92 lb ai/A (1.4 to 2.8 gal/A)
Time  Apply midwinter immediately before a cold rain to reduce volatility and enhance weed suppression.
Remarks  Liquid formulation of encapsulated crystals of dichlobenil. Controls most germinating seeds and seedlings of annual and perennial grasses, and broadleaf weeds. Do not use on light sandy soils. Do not apply with high or gusty wind, high temperatures, low humidity, or temperature inversions. Inhibits cellulose and cell wall formation.
Caution  Use only around well established plants, typically wait until 1 yr after transplanting. Grazing livestock is prohibited. 
Site of action  Group 20: inhibits cell wall synthesis Site A
Chemical family  Nitrile
•  dichlobenil (Casoron) 
apples, pears, cherries, and hazelnuts
Rate  4 to 6 lb ai/A (100 to 150 lb/A Casoron)
Time  Apply midwinter immediately before a cold rain to reduce volatility and improve weed suppression.
Remarks  Weigh and distribute over precisely measured area to ensure accurate application. Do not apply until 4 wk after transplanting. Oregon results over 9 yr suggest perennial weeds can be suppressed with 4-, 3-, and 2-lb ai/A rates applied during 3 consecutive years. Inhibits cellulose and cell wall formation.
Caution  Grazing livestock is prohibited. 
Site of action  Group 20: inhibits cell wall synthesis Site A 
Chemical family  Nitrile
•  diuron (Karmex DF and others)
apples, pears, peaches, hazelnuts, and walnuts only
Rate  See label for crop-specific application rates.
Time  Apply higher rate in late fall, or split applications in spring and fall to bare soil, depending on soil type.
Remarks  Add a foliar-active herbicide to control existing vegetation. Consult label for information on rates and soil types. Reduce rates after effective weed control is achieved. Can be rotated with simazine or other herbicides to reduce weed shifts. Inhibits photosynthesis.
Caution  Do not apply to sandy or gravelly soils or to full-dwarf rootstocks. Use only on trees established at least 1 yr (3 yr for peaches). Do not apply if nuts are on the ground.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  simazine (Princep Caliber 90 and 4L)
except chestnuts, apricots, prunes, and nectarines
Rate  1.6 to 4 lb ai/A (1.6 to 4 quarts/A Princep 4L; 1.75 to 4.4 lb/A Caliber 90)
Remarks  Oregon special local needs label (OR-080038) on sweet cherries for Princep Caliber 90 for use where soils have some buffering capacity by partially adsorbing herbicide. Tart cherries have a Section 3 label for Princep 4L in both Oregon and Washington.
Caution  Do not apply on light, sandy, or rocky soils with little organic matter. Trees must be established 2 yr or more. Note comments above.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Triazine
•  terbacil (Sinbar 80)
bearing apples and peaches only; labeled on nonbearing apricot pear, apple, cherry, peach, and plum
Rate  0.4 to 0.8 lb ai/A (0.5 to 1 lb/A), newly established; 2 to 4 lb/A Sinbar depending on soil type.
Time  Apply spring or fall before weeds germinate or when they are in early seedling stage.
Remarks  Consult label for rates, soil types, and organic matter contents. Reduce rates after weeds are controlled. Avoid use for 2 yr if replanting is anticipated. Grazing is prohibited. 
Caution  Do not apply to sandy or gravelly soils or to soils with less than 1% organic matter. Use only on orchards established at least 3 yr. Can be rotated with diuron or other herbicides (except simazine) to reduce weed shifts. Do not contact crop foliage or fruit with herbicide spray. Has greater water solubility than diuron or simazine.
Site of action  Group 5: photosystem II inhibitor
Chemical family  Uracil
•  norflurazon (Solicam)
except chestnuts
Rate  1.97 to 7.8 lb ai/A (2.5 to 10 lb/A Solicam)
Time  Apply in fall to early spring before weeds emerge, to soil relatively free of plant residues.
Remarks  Activation requires ample irrigation or rain within 2 to 4 wk. See label for rates and soil types. Orchards must be established at least 18 mo except for newly planted apples which can be treated after soil settles around tree roots. In cherries, use lower rates and rotate with other soil-applied herbicides to reduce chances of phytotoxic carryover. Avoid contact with fruit and crop foliage. Inhibits yellow pigment formation, causing bleaching of green chlorophyll.
Caution  Do not graze livestock in treated area. 
Site of action  Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family  Pyridazinone
•  napropamide (Devrinol)
except chestnuts
Rate  5.0 lb ai/A (50 lb/A Devrinol 10G)
Time  Apply fall through spring before weeds germinate, or mix with foliar-active herbicide to control existing vegetation.
Remarks  Irrigation or shallow incorporation is recommended for treatments made November through February if no rain falls within 2 wk after treatment. Irrigate within 24 hr to wet the soil 2 to 4 inches deep when applied March through October. Results are best if herbicide is mechanically incorporated into the soil immediately after application. Performance is reduced when excessive plant residues are on soil surface. Inhibits root growth.
Caution  Do not apply to frozen soil. Do not graze livestock in treated area. 
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Acetamide
•  oryzalin (Surflan AS)
except apples, cherries, nectarines, peaches, prunes, and walnuts
Rate  2 to 6 lb ai/A (2 to 6 quarts/A Surflan)
Time  Apply late fall or early spring to bare soil or after tillage or a foliar-active herbicide has destroyed existing vegetation.
Remarks  Use higher rates for longer residual control. Irrigate with 0.5 inch of water or rain to activate herbicide. Shallow cultivation can control newly germinated weeds without reducing herbicide activity. Inhibits mitosis, primarily in roots.
Caution  Grazing is prohibited. 
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  pronamide (Kerb)
except apricots, hazelnuts, and walnuts
Rate  1 to 4 lb ai/A (2 to 8 lb/A Kerb 50W)
Time  Apply once a year, in fall after harvest, but before leaves drop and soil freezes. 
Remarks  Apply to soil relatively free of plant residues. Requires moisture from rain, snowmelt, or irrigation to activate. Use lower rates for annual grasses and susceptible broadleaf weeds; higher rates for perennials such as quackgrass. Use only on orchards established at least 6 mo. Inhibits root growth.
Caution  A restricted-use pesticide. Do not graze livestock in treated area. 
Site  of action  Group 3: microtubule assembly inhibitor
Chemical family  Benzamide
•  trifluralin (Treflan 4EC) 
except on apples, pears, cherries, and hazelnuts,
Rate  0.5  to 1 lb ai/A (1 to 2 pints/A Treflan 4EC)
Time  Apply preemergence for annual and broadleaf weed control.
Remarks  Consult label for calibration and application instructions. Use to supplement other weed control practices.
Caution  Apply only when wind speed and direction minimize drift to nontarget areas. Avoid contacting fruit and foliage with treated irrigation water. Prevent groundwater contamination by following all requirements of the irrigation system.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  oxyfluorfen (Goal 2XL)
Rate  1.25 to 2 lb ai/A (5 to 8 pints/A Goal 2XL)
Time  Apply only beneath healthy trees. Direct spray toward tree base, avoiding direct plant contact. Acts as contact, either directly on broadleaf weeds or at soil surface as weeds emerge.
Remarks  Controls broadleaf weeds pre- and postemergence depending on application rate and weed species.
Site of action  Group 14: inhibits protoporphyrinogen oxidase
Chemical family  Diphenylether
•  pendimethalin
supplemental labels for Prowl H2O on bearing stone and pome fruit, trees, and nuts
Rate  1.9 to 3.8 ai/A (2 to 4 quarts/A Prowl H2O), depending on desired length of control
Time  Apply as a broadcast or banded treatment beneath trees and/or in areas between rows, before weeds emerge.
Remarks  Adequate rain or irrigation after application and before weed seedlings emerge will provide the most effective weed control. Preharvest interval is 60 days.
Caution  Do not apply over the tops of trees or to leaves, shoots, or buds, or injury may occur. Do not feed forage or graze livestock. Do not exceed 6.3 quarts/A per year. (Inhibits mitosis in roots and shoots.)
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
ORCHARD CROPS—Established Plantings—Postemergence Contact and Translocated Herbicides
•  paraquat (Gramoxone Max, Firestorm)
Rate  0.625 to 1 lb cation/A (2.5 to 4 pints/A Gramoxone, 1.7 to 2.7 pints/A Firestorm)
Time  Apply as a directed spray toward tree base; ensure complete wetting when weeds are small.
Remarks  Add a nonionic surfactant or crop oil concentrate as label specifies; take care to avoid anionic formulations that react in the tank to form insoluble precipitates. Acts as contact; absorbs energy produced by photosynthesis, forming peroxides that disrupt living cells.
Caution  A restricted-use pesticide. Do not ingest or inhale spray mist. Wear protective shields, respirators, and clothing. Do not let spray contact foliage, fruit, or young tree trunks. Do not graze treated areas. 
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  oxyfluorfen (Goal 2XL)
Rate  1.25 to 2 lb ai/A (5 to 8 pints/A Goal 2XL)
Time  Apply only to healthy trees. Direct spray toward tree base, avoiding direct plant contact. Acts as contact, either directly on broadleaf weeds or at soil surface as weeds emerge. Weeds must be small for postemergence control.
Remarks  Controls broadleaf weeds pre- and postemergence depending on application rate and weed species.
Site of action  Group 14: inhibits protoporphyrinogen oxidase
Chemical family  Diphenylether
•  glyphosate (numerous product names)
Rate  Spray—read label carefully for crops listed and geographic location
Time  Apply to actively growing weeds.
Remarks  Select application equipment to prevent crop injury by directing spray or by using selective applicators. Adjust concentration depending on equipment, or consult label about rate and time of application, especially for perennial weeds. Avoid treating root suckers in late summer when spraying wild blackberries or other weeds. Additional surfactant or ammonium sulfate according to label instructions may improve control of slightly stressed weeds. Inhibits production of three amino acids and protein synthesis.
Caution  Do not treat pear root suckers. Do not spray foliage or green bark. Preharvest interval is at least 14 days. If repeat applications are necessary, do not exceed a total of 10.6 lb ai/A in 1 yr. Grazing is prohibited. Repeated glyphosate applications have created resistant biotypes of ryegrass in Australian orchards. To avoid weed resistance, rotate and mix weed control practices. 
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glyphosate (several products)
Rate  Wiper—use 33% solution
Remarks  Apply 1 gal product with 2 gal water and wipe weeds; avoid contact with desirable vegetation. In severe infestations, reduce equipment ground speed or apply in two directions to ensure wiper contact. See remarks above.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glufosinate ammonium (Rely)
apples, hazelnuts, and walnuts
Rate  0.75 to 1.5 lb ai/A (3 to 6 quarts/A Rely)
Time  Apply to actively growing weeds as a directed spray or spot treatment according to stage of weed growth.
Remarks  Avoid drift to or treatment of desirable foliage or green bark during establishment year.
Caution  Do not exceed 4.5 lb ai/A per 12-mo season. Do not graze or apply within 14 days of harvest.
Site of action  Group 10: inhibits glutamine synthetase
Chemical family  Phosphinic acid
•  2,4-D amine (Saber, Weed Rhap A-4D, or Dri-Clean Herbicide)
Rate  0.95 to 1.4 lb ae/A (2 to 3 pints/A Saber for stone fruits and nuts only); 3 pints/A for Weed Rhap A-4D)
Time  Do not apply during bloom. Preferred timing is late autumn after harvest but before first frost. Apply after irrigation rather than before, to avoid moving the herbicide into the root zone. Apply as a directed spray as needed to young, actively growing weeds in the prebud to early bud stage of growth.
Remarks  Apples and pears: Minimize use in pears after fruit set due to possibility of early ripening. Apparently, Gala, Fuji, and Golden Delicious apples are more sensitive to 2,4-D than are other cultivars. Do not allow spray to contact pear leaves, fruit, tree trunks, or root suckers. Preharvest interval is 14 days.
Stone fruits and nuts: 2,4-D can be applied up to twice per season. Preharvest interval is 40 days for stone fruits, 60 days for nuts. Application timing on other fruits and nuts excludes Preharvest interval requirements. Mimics natural plant hormones.
Caution  Avoid high pressures or other factors that can increase drift. Reduce possible root uptake by avoiding irrigation or rain within 10 days after application. Do not use on light, sandy, or bare soils. Do not use when temperatures exceed 90°F. Do not graze or feed cover crops from treated areas to livestock. 
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  clopyralid (Stinger)
stone fruits only
Rate  0.12 to 0.25 lb ae/A (0.33 to 0.66 pint/A Stinger)
Time  Make one to four broadcast applications to rosettes of Canada thistle that have emerged but before bud stage and at least 30 days before harvest.
Remarks  Including apricots, Chickasaw plums, Damson plums, fresh prunes, Japanese plums, nectarines, peaches, plums, plumcots, sweet cherries, and sour cherries. 
Postemergence control of clover, dandelion, horseweed, night-shade (black and hairy), annual sowthistle, Canada thistle, musk thistle, and vetch. Do not exceed a total of 0.66 pint/A product per year. Apply in 10 gal/A of water or more.
Caution  Preharvest interval is 30 days.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  rimsulfuron (Matrix FNV)
all fruit and nut crops
Rate  0.063 lb ai/A (4 oz/A Matrix FNV per year)
Time  Applied before or shortly after weed emergence, fall or spring depending on weed species targeted.
Remarks  Apply as a broadcast or banded application, avoiding foliage, fruit, and desirable suckers. One application per year unless banding, then two applications area allowed with a maximum application of 4 oz/A on a broadcast basis. Apply when rain and cool temperatures are expected. Results are best if soil is moist at time of application and with 0.5 inch of rain or irrigation within 2 wk after application. Postemergence control is best if weeds are small and an adjuvant is used. Preemergence and postemergence control of a number of grasses and summer annuals including puncturevine, dandelion, mallow, and quackgrass; postemergence partial suppression of yellow nutsedge. Preharvest interval is 7 days for pome fruit and 14 days for stone fruit and nuts. 
Caution  Trees must be established for 12 mo. Avoid spray drift onto adjacent crops. Clean spray tank carefully. Minimize contact with fruit or foliage. 
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  halosulfuron (Sandea)
nut crops only, nutsedge control
Rate  0.032 to 0.062 lb ai/A (0.66 to 1.33 oz/A)
Time  Apply in spring when nutsedge is not drought stressed.
Remarks  Maximize the interval between application and irrigation. Trees must be established at least 12 mo. Apply as a directed application at the base of the trees. Sandea also has soil residual activity and controls several broadleaved species, in addition to suppression of yellow nutsedge. 
Caution Take extreme care to avoid applying to stems, leaves, roots, or green bark of trees. Avoid spray drift onto adjacent crops. Clean spray tank carefully. 
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea
•  fluazifop (Fusilade DX)
except bearing apples, pears, chestnuts, and walnuts; labeled in nonbearing pears
Rate  0.25 to 0.375 lb ai/A (16 to 24 oz/A Fusilade DX). Refer to specific grassy weeds listed on label.
Time  Apply to actively growing grasses or within 7 days after irrigation as a directed spray with 1% crop oil or 0.25% nonionic surfactant.
Remarks  Identify grasses and adjust rates depending on susceptibility and stage of weed growth as label instructs. Results often are erratic on grasses stressed from lack of vigor, high temperature, low fertility, or drought. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescues resist treatment. Inhibits fatty acid production, cell membranes, and new growth.
Caution  Do not exceed 4.5 pints/A total per season. Preharvest interval is 14 days. Grazing is prohibited. 
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  sethoxydim (Poast)
except prunes and plums
Rate  0.28 to 0.47 lb ai/A (1.5 to 2.5 pints/A Poast)
Time  Apply at optimum growth stage listed on the label.
Remarks  Identify susceptible grasses and add 2 pints/A of a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues; quackgrass can be suppressed. Note maximum annual amounts per acre listed on label. Inhibits fatty acid production, cell membranes, and new growth.
Caution  Preharvest interval is 14 days for apples and pears; 25 days for apricots, cherries (sweet and sour), nectarines, and peaches; 15 days for nuts. 
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
ORCHARD CROPS—Green Sucker Control in Hazelnuts
•  paraquat (Gramoxone Max)
Rate  0.625 to 1 lb ai/A (2.5 to 4 pints/A Gramoxone)
Time  Apply three to four times per season when suckers are 6 to 9 inches long but before they become woody.
Remarks  Add a nonionic surfactant or crop oil concentrate as label specifies, taking care to avoid anionic formulations that react in the tank to form insoluble precipitates. Direct spray toward green suckers at tree base. Acts as contact; absorbs energy produced by photosynthesis, forming peroxides that disrupt living cells.
Caution  A restricted-use pesticide. Do not ingest or inhale spray mist. Wear protective face shields, respirators, and clothing.  Do not allow spray to contact foliage or fruit. Avoid windy conditions and drift. Do not graze treated areas. Do not apply when nuts are on the ground. Do not exceed three postemergence directed applications per season for these crops. Preharvest interval is 14 days for peaches; 28 days for apricots, cherries, and nectarines. 
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  2,4-D (Saber or Orchard Master)
Rate  0.7 to 0.95 lb ae/A (1.5 to 2 pints/A Saber); consult label
Time  Apply in 100 gal/A water; add nonionic spreader-sticker. Apply to suckers 6 to 9 inches long.
Remarks  Spray to runoff as needed up to four times per year from April through August, using large-orifice nozzles to reduce possible drift. Mimics natural plant hormones.
Caution  Preharvest interval is 45 days. Grazing is prohibited. 
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  glufosinate ammonium (Rely)
Rate  1 lb ai/A (4 quarts/A Rely)
Time  Direct spray to cover all sucker foliage.
Remarks  Split applications about 4 wk apart to improve control.
Site of action  Group 10: inhibits glutamine synthetase
Chemical family  Phosphinic acid
•  carfentrazone-ethyl (Aim EC)
Rate  0.031 lb ai/A (2 fl oz/A Aim EC)
Time  Direct spray to immature green suckers at base of tree.
Remarks  Read label for additional options.
Site of action  Group 14: inhibits protoporphyrinogen oxidase
Chemical family  Triazinone
ORCHARD CROPS—Grass Suppression in Row Middles (chemical mowing)
•  glyphosate (numerous product names)
Rate  Read label carefully for crops listed and geographic location
Time  Apply 6 to 8 oz/A to suppress (chemically mow) perennial grass covers between tree rows in orchards.
Remarks  Use the 8 oz/A rate to treat tall (coarse) fescue, fine fescue, orchardgrass, or quackgrass covers. For best suppression of these species, add ammonium sulfate at 1.7 lb/10 gal of spray solution. Use the 6 oz/A rate, without ammonium sulfate, when treating Kentucky bluegrass covers. Apply treatments in 20 gal/A spray volumes to actively growing grass covers. For best spray distribution and coverage, use flat fan nozzles. Additional nonionic surfactant may be added at 0.5% concentration when using surfactants with at least 50% ai, or a 1% surfactant concentration for those with less than 50% ai. For best results, mow grass in spring for uniformity, then apply appropriate rate 3 or 4 days after mowing. Low rates will not adequately suppress broadleaf weeds such as  dandelion or plantain. If broadleaf weeds infest more than 10% of ground cover, tank-mix 2,4-D  labeled for orchard use.
Caution  Do not treat grass covers under poor conditions such as drought stress (drip irrigation), disease, or insect damage; suppression may be poor. Repeated glyphosate applications have created resistant biotypes of ryegrass in Australian orchards.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  sethoxydim (Poast)
Rate  0.09 lb ai/A (0.5 pint/A Poast)
Time  Apply to orchard floor middles one time only, to suppress growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
ABANDONED ORCHARDS—Treat Unwanted Trees
•  triclopyr + 2,4-D (Crossbow)
Washington only
Rate  Washington special local needs label only (WA-010038). Consult label for mixing and application rate instructions for basal application or hack-and-squirt methods.
Caution  Do not replant susceptible broadleaf trees within 12 mo of application.
Site of action  (both) Group 4: synthetic auxin
Chemical family  (triclopyr) pyridine; (2,4-D) phenoxy acetic acid