Professional Landscape Maintenance
Ed Peachey 
Revised November 25, 2008
Weed management in professionally managed landscapes requires a thorough knowledge of the weeds, weed control practices, application options, plant tolerances, and management strategies. Success with any method depends on thorough planning, properly selecting control methods, and effective timing. When selecting chemicals for weed control, you must understand the subtle differences in application techniques, residual activities, susceptibilities and timing for control of target species, tolerance of desirable plants, potential for weed shifts, and long-term effects of integrating site objectives and year-round weed management strategies. Often, treatments must be repeated or combined with other practices for maximum control.
Weed shifts   Weed infestations are dynamic and change depending on previous cultural and weed control practices. For example, routine use of the same or similar herbicides will result in a shift to weed species that tolerate the treatment. Repeated use of simazine in nurseries was first demonstrated to cause a shift within a natural population of common groundsel. Since then, more than 35 species represented in 17 genera have been reported to tolerate triazine herbicides.
Preventing weed shifts   Weeds that survive repeated use of the same or similar herbicides must be eliminated before the tolerant species or biotypes become established. Spot-treat or hand pull weeds and combine these methods with other weed management practices to minimize the occurrence of resistant biotypes.
Managing weedy vegetation   Successful weed control in landscapes requires a comprehensive or year-round approach whereby a combination of weed control practices is employed and alternated over several years. Development of these strategies requires knowledge of each weed and weed control practice. Weeds must be identified and information gathered about the effectiveness of each weed control practice. Consider costs and select herbicide combinations that can be applied together or in split applications that control the weeds present in the landscape. Note the action of each herbicide or how the chemical works in the plant. Then tank-mix and alternate use of these products to reduce the chance of developing resistant species or biotypes. Often a combination of mechanical, herbicidal, and sometimes hand removal or spot treatment with herbicide sprays or wipers will provide the most effective year-round control.
Soil-active herbicides   Persistent, soil-applied herbicides can be applied to weed-free soil during winter when rain will activate the chemical. Some compounds may be applied throughout the year if irrigation is available. Apply lower rates on sandy soils having lower clay or organic matter, or cation exchange capacities. Existing vegetation can be controlled by mixing the soil-active herbicide with a post-emergence contact or translocated herbicide, provided such a mix is not prohibited by either label. Consult labels for listed species and duration of expected control.
Postemergence herbicides   In landscape plantings, postemergence weed control requires precision since few options exist. Postemergence treatments either selectively control susceptible weeds or are applied with selective equipment. Frequent scouting aimed at identifying susceptible weeds and the correct stage of weed growth must be combined with appropriate weather conditions and labeled spray additives to maximize control. Consult each label for numerous precautions or information about crop or cultivar tolerances. Always test new products on selected plants before adopting their use throughout your operation.
Caution!  Information provided in this handbook is not intended to be a complete guide to herbicide use. Before using any chemical, read the recommendations on the label. Before a chemical can be recommended for a specific use, it must be thoroughly tested. The recommendation on the manufacturer’s label, when followed, can prevent many problems from arising from the wrong use of a chemical.
Note   Herbicides must be applied at exactly the correct rate and time to selectively control weed growth with minimal chance for injury to nursery crops. Obtain more consistent results by reading the herbicide label and other information about the proper application and timing of each herbicide. Suggested rates listed in this guide are stated as pounds active ingredient per acre (lb ai/A) or pounds acid equivalent per acre (lb ae/A). Calibrate your equipment precisely and verify exact application rates, especially to irregular landscape sites.

Established Tree, Shrub, Rose, and Ground Cover Landscapes
(Multiply rate by 0.023 for amount per 1,000 sq ft)
•  geo-textiles
available at agricultural and garden supply stores
Spunbonded fabrics (nonwoven): lightweight, extruded polypropylene fibers; requires 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. Surface is slick and causes rapid wetting and drying to prevent weed establishment except for perennial rhizomes that can penetrate the laminate; most expensive geo-fabric.
Professional landscapes—Established Landscapes—Soil-applied
•  dichlobenil (Casoron 4G)
no ground covers
Rate  4 to 6 lb ai/A (100 to 150 lb/A granular product)
Time  Apply midwinter immediately before a cold rain to reduce volatility and enhance weed suppression. 
Remarks  Weigh and distribute uniformly and exactly over precisely measured areas to ensure accurate applications. Oregon results over 9 yr suggest perennial weeds can be suppressed with 4-, 3-, and 2-lb ai/A rates applied in 3 consecutive years. Grazing livestock is prohibited. Inhibits cellulose and cell wall formation.
Site of action  Group 20: inhibits cell wall synthesis Site A 
Chemical family  Nitrile
•  napropamide (Devrinol 2G)
Rate  4 to 6 lb ai/A (200 to 300 lb/A)
Time  Apply any time to weed-free soil and sprinkler irrigate to wet soil 1 to 2 inches deep, or apply during midwinter rains in western Oregon for annual weed control. 
Remarks  Use higher rates with severe weed populations or when broadleaf weeds are present. Primarily grass control Inhibits root growth.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Acetamide
•  oryzalin (Surflan AS)
Rate  2 to  4 lb ai/A (2 to 4 quarts/A) depending on length of control
Time  Apply any time to weed-free soil and sprinkler irrigate with 0.5 inch if no rain falls within 1 wk, or cultivate 1 inch deep to activate herbicide for annual weed control.
Remarks  Consult label for tolerant ornamental species. Primarily grass control. Inhibits mitosis, primarily in roots.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  pendimethalin (Pendulum 2G or Corral 2.86G Ornamental Weedgrass Control) 
Rate  2 to 4 lb ai/A (100 to 200 lb/A Pendulum 2G) depending on desired length of weed control
Time  Apply at time of planting or before weed seed germinates.
Remarks  Primarily for grass control. Soil should be loose and free of all established weeds. Water within a few days to activate herbicide before weeds emerge. Inhibits mitosis in roots and shoots.
Caution  Granules may stain stone, wood, or other porous surfaces.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  prodiamine (Barricade 65WG or Endurance)
Rate  0.65 to 1.5 lb ai/A (1 to 2.3 lb/A) depending on desired length of weed control
Time  Apply any time to weed-free soil and incorporate with 0.5 inch water or rain within 14 days. 
Remarks  May be applied to newly transplanted and established ornamentals as a broadcast, over-the-top spray. Activate with 0.5 inch of rain or irrigation water or with shallow incorporation. Inhibits germination and root development.
Caution  Do not exceed 2.3 lb/A in any 12-mo period. 
Site of action  Group 3: microtubule inhibitor
Chemical family  Dinitroaniline
•  S-metolachlor (Pennant Magnum)
Rate  1.24 to 2.48 lb ai/A. 1.3 to 2.6 pints/A
Time  Apply as direct spray toward base of desired plant, either to established ornamentals or 5 days after transplanting.
Remarks  Existing weeds must be removed. Primarily targets grasses but controls some broadleaves and suppresses nutsedge.  Inhibits seedling roots and/or shoots.
Caution  Do not apply more than twice per year. Consult label for tolerant ornamentals.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Chloroacetamide
•  dithiopyr (Dimension 1EC)
Rate  0.375 to 0.5 lb ai/A (1.5 to 2 quarts/A) 
Time  Apply preemergence around bases of ornamental plants in landscape.
Remarks  For best results, prepare a weed-free surface with minimal clods and leaf debris.
Caution  Do not exceed 1.5 fl oz/1,000 sq ft every 3 to 4 mo or 4.5 fl oz/1,000 sq ft/yr. Do not apply to plant roots or weakened ornamental plants or when drift potential is moderate to high. Do not use in enclosed structures. Dithiopyr is toxic to fish and highly toxic to oysters, shrimp, and other aquatic organisms.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Pyridine 
•  oxadiazon (Ronstar 2G)
Rate  2 to 4 lb ai/A (100 to 200 lb/A) depending on target weed species
Time  Apply any time to weed-free soil and irrigate with 0.25 to 0.33 inch water immediately after applying for annual weed control.
Remarks  Do not cover with soil or mulch or incorporate, as weed control will desist. Weeds in the pink family (chickweed, mouseear chickweed, and pearlwort) are resistant. Primarily broadleaf control (controls weed seedlings by contact action during emergence.)
Caution  See label for sensitive ornamentals, which include varieties of rhododendron, spruce, hemlock, azalea, viburnum, and cotoneaster. Avoid contaminating water intended for irrigation. Do not use on plants that will produce fruit within 1 yr.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Oxadiazole
•  isoxaben (Gallery 75 DF)
Rate  0.495 to 0.998 lb ai/A (0.66 to 1.33 lb/A)
Time  Apply late summer to early fall, in early spring, or immediately after cultivation. Apply to debris-free soil surface.
Remarks  Identify weeds; adjust rates according to charts on label. Activate with 0.5 inch water or shallow cultivation before weeds emerge. Chemical stability remains adequate when left on soil surface for 21 days. Primarily controls broadleaves.
Caution  Do not apply to newly transplanted crops until media settle. See label for 14 sensitive ornamental species for which isoxaben is not recommended, including hydrangea, purple coneflower, and yucca. Use untreated soil to fill around transplants if isoxaben has been applied within 1 yr. 
Site of action  Group 21: inhibits cell wall synthesis Site B
Chemical family  Benzamide
•  EPTC (Eptam 7E)
Rate  5 to 14.9 lb ai/A (5.75 to 17 pints/A) depending on target species
Time  Apply and immediately incorporate 2 to 3 inches deep with a rototiller 2 wk before transplanting balled or canned stock; or, spray postplant and incorporate with tillage. In spring, apply around established plants after growth and incorporate.
Remarks  Use higher rates for perennial weed control and incorporate to a depth of 6 inches with a rototiller. Note sensitive flowers listed on label. Primarily for grass control including quackgrass suppression. Inhibits shoot growth.
Site of action  Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family  Thiocarbamate
•  DCPA (Dacthal W-75)
Rate  4.5 to 10.5 lb ai/A (6 to 14 lb/A) depending on soil type and target weeds
Time  Apply to weed-free soil in early spring or late summer for control of susceptible winter weeds for annual weed control.
Remarks  Performs erratically west of the Cascades. Sprinkler-irrigate after application to activate herbicide. Inhibits mitosis in roots and shoots.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Phthalic acid
ESTABLISHED LANDSCAPES—Convenient Soil-applied Premixes—Combined Grass and Broadleaf Herbicide
•  isoxaben + trifluralin (Snapshot 2.5TG) 
Rate  200 lb/A
Time  Apply to weed- and debris-free soil. Soil must be settled with water and free of cracks after transplanting.
Remarks  Activate within 31 days using 0.5 inch of water or shallow cultivation before weeds begin to emerge. Follow label instructions for repeat treatments.
Caution  Do not apply to unrooted liners or cuttings, bedding plants, or new-planted ground covers.
Site of action  (isoxaben) Group 21: inhibits cell wall synthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor
Chemical family  (isoxaben) benzamide; (trifluralin) dinitroaniline
•  benefin + oryzalin (XL 2G)
Rate  200 lb/A per application with at least 2 mo between applications; do not exceed 800 lb/A/yr
Time  Apply before target weeds germinate. 
Remarks  Precisely calibrate application equipment, preferably at half rates, to enable two perpendicular passes for increased accuracy. Inhibits cell division or mitosis, primarily in roots.
Caution  Sensitive species include Douglas-fir, eastern hemlock, and begonia.
Site of action  (both) Group 3: microtubule assembly inhibitor
Chemical family  (both) dinitroaniline
•  oxyfluorfen + oryzalin (Rout)
Rate  50 to 100 lb/A (2% + 1% formulation, respectively)
Time  Apply uniformly either in spring before weed seed germination and crop growth flush or to weed-free soil.
Remarks  Requires 0.5 inch water immediately after application to activate and to wash product from leaves. Acts as contact-type herbicide and inhibits cell division or mitosis in roots and shoots, respectively.
Caution  Do not apply to wet foliage or plants with whorls. Note all other precautions on label.
Site of action  (oxyfluorfen) Group 14: protoporphyrinogen oxidase inhibitor; (oryzalin) Group 3: microtubule assembly inhibitor
Chemical family  (oxyfluorfen) diphenylether; (oryzalin) dinitroaniline
•  napropamide + oxadiazon (Pre Pair)
Rate  100 to 150 lb/A product
Time  Apply uniformly any time to weed-free surface.
Remarks  Newly planted stock can be treated when soil settles after first irrigation. Activate with overhead irrigation.
Caution  Do not apply in greenhouses or to wet foliage.
Site of action  (napropamide) Group 15: inhibits very long chain fatty acid synthesis; (oxadiazon) Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  (napropamide) acetamide; (oxadiazon) oxadiazole
•  oxadiazon + prodiamine (RegalStar G)
Rate  200 lb/A
Time  Any time during the year, but before weed seeds germinate.
Remarks  Cultivating or disturbing the soil after application diminishes weed control.
Caution  Do not apply herbicide granules to wet foliage. Cultivars of Ilex spp. (holly) and Rhododendron spp. may be sensitive to this product.
Site of action  (oxadiazon) Group 14: protoporphyrinogen oxidase inhibitor; (prodiamine) Group 3: microtubule assembly inhibitor
Chemical family  (oxadiazon) oxadiazole; (prodiamine) dinitroaniline
ESTABLISHED LANDSCAPES—Postemergence
•  glyphosate (numerous product names)
not for ground covers
Rate  Spray 1.5 to 5 lb ai/A or 1 to 2% solution for high-volume sprayers
Time  Apply as directed spray toward base of bush when weeds are actively growing or moving sugars to roots.
Remarks  Use lower rates for annual weeds; consult label for higher rates and time of application for perennial weeds. Expedite Application Equipment contains a special formulation using small-droplet technology. Inhibits production of three amino acids and protein synthesis.
Caution  Do not spray green foliage or green bark. If applications are repeated, do not exceed a total of 10.6 lb ai/A (10.6 quarts/A) in 1 yr. Repeated use in Australian orchards for several years has resulted in resistant biotypes. To avoid developing weed resistance, rotate chemicals and weed control practices. 
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glyphosate (several products)
not for ground covers
Rate  Wiper—use 33% solution
Time  Apply 1 gal product to 2 gal water and wipe weeds. Avoid 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 (Finale)
spot or directed spray only
Rate  Consult label
Time  Apply to thoroughly cover actively growing weeds. Avoid all contact with desirable foliage and green bark.
Remarks  To trim or edge landscape plantings.
Site of action  Group 10: glutamine synthase inhibitor
Chemical family  Phosphinic acid
•  pelargonic acid (Scythe)
Rate  Broadcast—use 5 to 10 gal product per 100 gal water. Spot spray—use 5 to 10% solution (6.67 to 13 fl oz/gal) to cover 400 sq ft.
Time  Apply to thoroughly wet foliage, either broadcast to noncrop area or preemergence to ornamental crop; or spot treat and trim around ornamentals, trees, flower beds, paths, and drives.
Remarks  Controls small, actively growing weeds and weakens established weeds by removing susceptible vegetation. Disrupts cell membranes, causing leakage and symptoms of leaf burn. 
Site of action  Group 26: unknown
Chemical family  Carboxylic acid
•  clove leaf oil (Matran EC)  
Rate  5 to 8% dilution in 25 to 100 gal of water, depending on weed size, temperature, and sunlight intensity.
Time  Before weeds are 6 inches tall.
Remarks  OMRI-listed and WSDA-approved herbicide for in-crop use. Apply before crop emergence, or between rows after emergence, avoiding contact with desirable foliage. Directed sprays or hooded sprayers are recommended. Works best on annual weeds less than 6 inches. Performance may be erratic depending on environmental conditions. Bright sunlight improves efficacy. No preharvest interval or reentry interval.
Caution  Use appropriate nozzles to prevent drift onto desirable foliage.
•  lemon grass oil (Green Match EX)  
Rate  7 to 15% dilution depending on weed size and species.
Time  When weeds are less than 6 inches tall.
Remarks  OMRI-listed, NOP-compliant, and WSDA-approved organic burndown herbicide for use in crop and noncrop sites. Green Match damages foliage on contact; leaf damage is visible within hours. Directed sprays or hooded sprayers are recommended. Coverage is very important. Cool weather may slow activity. No reentry interval. Fast wilting or necrosis of leaves due to removal of waxy cuticle.
Caution  Use appropriate nozzles to prevent drift onto desirable foliage.
•  halosulfuron-methyl (Sedgehammer)
Rate  0.031 to 0.062 lb ai/A (0.66 to 0.33 oz/A) to three- to eight-leaf nutsedge
Time  Post-directed spray on established woody ornamentals
Remarks  For control of nutsedge. Use lower rate on light infestations and high rate on heavy infestations. Do not exceed 5.33 oz/A or four applications per year. Add a nonionic surfactant at 0.25 to 0.5% v/v. May tank-mix with glyphosate.
Caution  Do not apply over the top of desirable flowers, ornamentals, vegetables, trees, or shrubs.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Sulfonylurea 
•  fluazifop (Fusilade II or Ornamec)
Rate  Consult labels
Time  Apply to actively growing grasses or within 7 days after irrigation as a directed spray with 0.25% nonionic surfactant when susceptible grasses are in the labeled growth stage.
Remarks  Identify grasses and adjust rates depending on susceptibility and stage of weed growth as label instructs. Results often are erratic if grasses are stressed from 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 tank-mix with other pesticides. Do not apply within 5 days of other pesticide treatments.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  sethoxydim (Segment)
crops listed on label
Rate  0.28 to 0.47 lb ai/A (36 to 60 fl oz/A)
Time  Apply at optimum growth stage of grasses listed on the label.
Remarks  Identify susceptible grasses. 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, but quackgrass can be suppressed. Inhibits fatty acid production, cell, membranes, and new growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  fenoxaprop ethyl (Acclaim Extra)
Rate  13 to 39 fl oz/A or /1,000 sq ft
Remarks  Adjust rates depending on number of grass tillers (see label). Ensure thorough coverage to actively growing, susceptible grasses. Repeat after grass begins active growth, but do not exceed 120 fl oz/A per season. Inhibits fatty acid production, cell membranes, and new growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  clethodim (Prism (registered only in Oregon) or Envoy)
Rate  Consult labels
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). Controls annual bluegrass. 
Caution  Do not exceed 68 fl oz/A per season. 
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
ESTABLISHED TREES, SHRUBS, ROSES, AND GROUND COVERS—Root Growth Control
•  spunbonded polypropylene + trifluralin (Biobarrier)
Rate  Consult label
Remarks  A geo-textile fabric containing permanently attached nodules of time-release herbicide prevents root encroachment when placed vertically, horizontally, or surrounding structures such as sidewalks, roads, building foundations, curbs, tennis courts, swimming pools, septic fields, or underground pipes or cables in the soil. Extend edge of fabric 18 inches beyond structure to prevent root growth around edges of protected structure. Maintain at least 4 inches of soil overlay. Both physical and mitotic inhibition of roots.
Site of action  (trifluralin) Group 3: microtubule assembly inhibitor
Chemical family  (trifluralin) dinitroaniline

Bulb and Flower Beds
(Multiply rate by 0.023 for amount per 1,000 sq ft)
•  oryzalin (Surflan AS)
bulbous iris, daffodil, hyacinth, and tulip
Rate  0.75 lb to 1.5 lb ai/A (0.75 to 1.5 quarts/A) depending on target species and time of year applied
Time  Apply 2 to 4 wk after planting ornamental bulbs but before annual weeds emerge.
Remarks  For fall-planted bulbs, apply in late winter to weed-free soil. Inhibits mitosis in roots and shoots.
Caution  Do not apply to emerged tulips taller than 0.75 inch.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  pendimethalin (Pendulum 2G) 
Rate  2 to 4 lb ai/A (100 to 200 lb/A) depending on desired length of weed control
Time  Apply before, during, or after planting bulbs. Apply to seeded wildflowers after flower seedlings have emerged but before weed seeds germinate. 
Remarks  May be applied to control susceptible weeds (primarily grasses) in bulbs (including crocus, daffodil, gladiolus, and tulip) and established wildflowers (including black-eyed Susan, California poppy, coreopsis, and oxeye daisy) listed on the label. Primarily for grass control. Soil should be loose and free of all established weeds. Water within a few days to activate herbicide before weeds emerge. Inhibits mitosis in roots and shoots.
Caution  Granules may stain stone, wood, or other porous surfaces.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  S-metolachlor (Pennant Magnum)
many blubs and flowers, except daffodil
Rate  1.24 to 2.48 lb ai/A (1.3 to 2.6 pints/A) depending on soil type and organic matter
Time  After transplanting
Remarks  Apply after transplanting and when soil has firmed around plant. Irrigate shortly after planting to wash the herbicide from foliage and to activate the herbicide in the soil. Will not control emerged weeds. Existing weeds must be removed. Primarily targets grasses but controls some broadleaves and suppresses nutsedge.  Inhibits seedling roots and/or shoots.
Caution  Consult label for tolerant and approved species. Do not apply more than twice per year. 
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Chloroacetamide
•  prodiamine (Barricade 65 WG)
see label for listed bulbs and wildflowers
Rate  0.65 to 1.5 lb ai/A (1 to 2.3 lb/A) depending on length of control desired and number of applications per year
Time  Apply before or after bulbs and wildflowers emerge but before weeds and desirable flowers emerge.
Remarks  Irrigate soon after treatment to wash herbicide onto the soil surface and to activate it within the top layer of soil. Do not exceed 2.3 lb/A.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
•  isoxaben (Gallery 75DF)
bulbous iris, daffodil, gladiolus, hyacinth, lily, and tulip
Rate  0.495 lb ai/A (0.66 lb/A)
Time  Apply 2 to 4 wk after planting, before bulbs and annual weeds emerge. Also may apply after bulbs emerge but before they flower.
Remarks  Activate with 0.5 inch water or shallow cultivation before weeds emerge. Chemical stability remains adequate when left on soil surface for 21 days. Primarily for broadleaf control.
Caution  Not for commercial production sites. Not recommended on tulips taller than 0.75 inch, or on gladiolus before emergence or if corms were less than 1 inch in diameter, or on bulbs while they are flowering.
Site of action  Group 21: inhibits cell wall synthesis Site B
Chemical family  Benzamide
•  benefin + oryzalin (XL 2G)
including bulbous iris, daffodil, hyacinth, and tulip
Rate  Bulbs—use 75 to 150 lb/A depending on soil texture and time of year; flowers—use 200 lb/A per application with at least 2 mo between applications, not to exceed 800 lb/A per year
Time  Apply before target weeds germinate or immediately after cultivation. For bulbs, apply 2 to 4 wk after planting but before weeds emerge.
Remarks  Consult label for tolerant flowers and bulbs. (Inhibits cell division or mitosis, primarily in roots.)
Caution  Do not apply to tulips emerged to 0.75 inch high or more, or to gladiolus before it emerges, or to plants less than 1 inch in diameter. Sensitive species include Douglas-fir, eastern hemlock, and begonia.
Site of action  (both) Group 3: microtubule assembly inhibitor
Chemical family  (both) dinitroaniline
•  EPTC (Eptam 7E)
Rate  5 to 14.9 lb ai/A (5.7 to 17 pints/A) depending on target weed species
Time  Apply 2 wk after transplanting herbaceous flowers in spring.
Remarks  For annual weeds, incorporate to 3 inches deep, use lower rate, and incorporate with nursery cultivator or rototillers. For perennial weeds such as nutsedge  and quackgrass, use higher rate and incorporate to 6 inches for suppression. Inhibits shoots of emerging seedlings.
Caution  All flowering bulbs, salvia, phlox, snapdragon, and ornamental pepper are susceptible to EPTC.
Site of action  Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family  Thiocarbamate
•  fluazifop (Fusilade II)
alyssum, marigold, petunia, geranium, iris, zinnia, and many others
Rate  0.25 to 0.375 lb ai/A (16 to 24 fl oz/A)
Time  Apply to actively growing grasses or within 7 days after irrigation with 0.25% nonionic surfactant when susceptible grasses are in the labeled growth stage. 
Remarks  Check label for crops that can be injured by over-the-top applications. 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, 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 tank-mix with other pesticides. Do not apply within 5 days of other pesticide treatments.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  sethoxydim (Segment)
chrysanthemum, coleus, gladiolus, impatiens, iris, marigold, snapdragon, petunia, zinnia, and others
Rate  0.28 to 0.47 lb ai/A (36 to 60 fl oz/A)
Time  Apply at optimum growth stage listed on the label.
Remarks  Identify susceptible grasses. 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, but quackgrass can be suppressed. Inhibits fatty acid production, cell membranes, and new growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  fenoxaprop ethyl (Acclaim Extra)
daylily and iris only
Rate  13 to 39 fl oz/A or 1,000 sq ft
Remarks  Adjust rates depending on number of grass tillers (see label). Ensure thorough coverage to actively growing, susceptible grasses. Repeat after grass begins active growth but do not exceed 120 fl oz/A per season. Inhibits fatty acid production, cell membranes, and new growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Aryloxyphenoxy propionate
•  clethodim (Envoy)
Rate  Consult labels
Time  Apply postemergence to actively growing annual or perennial grasses as listed on label.
Remarks  Consider environment and growth conditions that affect leaf uptake (see label).
Caution  Do not exceed 68 fl oz/A per season.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione

General Maintenance around Ornamental Plantings
•  diquat (Reglone)
Rate  0.5 lb ai/A
Time  Apply any time when weeds are small and actively growing.
Remarks  Avoid spray contact with desirable ornamental plants. Acts as a contact; absorbs electrons after photosynthesis and recycles herbicide.
Caution  A moderately toxic herbicide; protective gear required for handling and application. Do not ingest or inhale spray mist. Wear protective face shields, respirators, and clothing.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  glyphosate (numerous product names)
Rate  Spray—use 1.5 to 5 lb ai/A, or 1 to 2% solution for high-volume sprayers
Time  Apply as directed spray toward base of ornamental plant when weeds are actively growing or moving sugars to roots.
Remarks  Use lower rates for annual weeds; see label for higher rates and timing for perennial weeds. Expedite Application Equipment contains a special formulation using small-droplet technology.
Caution  Do not spray green foliage or green bark. If repeating applications, do not exceed a total of 10.6 lb ai/A (10.6 quarts) in 1 yr. 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—use 33% solution
Time  Apply 1 gal product to 2 gal water and wipe weeds, avoiding contact with desirable vegetation. 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
•  maleic hydrazide (Royal MH-30 SG)
Rate  7 to 10 lb gal product/30 to 50 gal water
Remarks  For edging turf. Label describes this use under “home lawns,” but gallon container restricts use to professional landscapers.

Herbicides for Large Food Gardens—Professional Use
(Multiply rate by 0.023 for amount per 1,000 sq ft)
LARGE FOOD GARDENS—Preemergence, Soil-applied Treatments 
•  napropamide (Devrinol 2G  Ornamental)
fruits and nuts
Rate  4 to 6 lb ai/A
Time  Apply to weed-free soil any time of year, although fall and winter applications are preferred. 
Remarks  Use higher rates for dense infestations containing many annual broadleaf weeds. Incorporate evenly in the top 1 to 2 inches of soil or irrigate within 2 to 3 days for best control.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Acetamide
•  trifluralin (Treflan EC)
certain vegetables
Rate  Consult label for rates on various vegetables, usually 0.5 to 0.75 lb ai/A (1 to 1.5 pints/A)
Time  Preplant-incorporate before seeding or transplanting vegetables.
Remarks  Note herbicide rates for soil types and crop groupings. Incorporate herbicide uniformly in the top 2 to 3 inches of soil to reduce evaporation of the product. Do not overapply.
Caution  Do not apply to sweet corn or to direct-seeded cucurbits, or serious injury may occur.
Site of action  Group 3: microtubule assembly inhibitor
Chemical family  Dinitroaniline
LARGE FOOD GARDENS—Postemergence, Directed or Foliar-applied Treatments for Vegetables, Trees, and Nuts
•  glyphosate (several products)
Rate  Consult labels
Time  Apply as a spray, spot treatment, or wiper application to actively growing weeds at least 7 days before planting vegetables and labeled tree or nut crops.
Remarks  Expedite Application Equipment contains a special formulation using small-droplet technology. Note all precautions, correct time of application for maximum weed control, and restrictions involving preplant application and preharvest intervals.
Caution  Apply only to crops listed on the label.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  clove leaf oil   (Matran EC)
Rate  5 to 8% dilution in 25 to 100 gal of water, depending on weed size, temperature, and sunlight intensity.
Time  Before weeds are 6 inches tall.
Remarks  OMRI-listed and WSDA-approved herbicide for in-crop use. Apply before crop emergence, or between rows after emergence, avoiding contact with desirable foliage. Directed sprays or hooded sprayers are recommended. Works best on annual weeds less than 6 inches. Performance may be erratic depending on environmental conditions. Bright sunlight improves efficacy. No preharvest interval or reentry interval.
•  lemon grass oil   (Green Match EX)
Rate  7 to 15% depending on weed size and species.
Time  When weeds are less than 6 inches tall.
Remarks  OMRI-listed, NOP-compliant, and WSDA-approved organic burndown herbicide for use in crop and noncrop sites. Green Match will damage foliage on contact; leaf damage is visible within hours. Directed sprays or hooded sprayers are recommended. Coverage is very important. Cool weather may slow activity. No reentry interval. Fast wilting or necrosis of the leaves due to removal of waxy cuticle.
•  sethoxydim (Poast)
Rate  0.28 lb ai/A (1.5 pints/A)
Time  Apply at optimum growth stage listed on the label.
Remarks  Labeled for use on many vegetable crops. Identify susceptible grasses and add 2 pints/A nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, 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 interval for some vegetables may be as long as 60 days. Apply only to listed vegetable crops.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione