dimethenamid-P (Outlook)
Rate 0.56 to 1 lb ai/A (12 to 18 oz/A product on coarse soils, 14 to 21 fl oz/A product on medium and fine soils).
Time Apply preemergence to weeds when hops are dormant or in early vegetative stages of growth. Incorporate with rainfall, sprinkler irrigation, or by mechanical means soon after application to maximize weed control.
Remarks Controls numerous annual grass weeds, yellow nutsedge, and certain broadleaf weeds when applied prior to emergence. Only one application allowed per season. Do not apply more than 21 oz/A per growing season. Preharvest interval is 60 days. If planting a cover crop between hop rows, be aware of possible injury to small grains or direct applications to hop rows only. Tank-mix with pendimethalin expands weed control spectrum.
Caution Contact of spray mixture with hop foliage may cause injury to hops. May only be applied by ground (banded) application (including postemergence-directed). Has not been tested on all soil types in the Pacific Northwest so test on a small area of field to confirm crop safety on the local soil type. When applied after planting, use over-head irrigation to rinse foliage and prevent damage.
Site of action Group 15: inhibits very long chain fatty acid synthesis
Chemical family Chloroacetamide
flumioxazin (Chateau SW, Chateau EZ, Redeagle, Tacoma, Tuscany SC, Warfox)
Rate 0.19 lb ai/A (6 oz/A of 51% ai products).
Time Apply to dormant hops November through February in a 1- to 1.5-foot band to each side of the hop row for preemergence weed control. Rain following application will improve preemergence weed control.
Remarks Do not apply more than 6 oz/A in a single application. Do not apply more than 6 oz/A during a growing season. Do not add an adjuvant. If weeds have emerged at the time of application, tank mix with a labeled herbicide such as paraquat or glyphosate to improve control of emerged weeds. Controls numerous broadleaf and some grass weeds when applied prior to emergence. Applications made closer to spring may cause temporary growth stunting to hops. If early crop vigor is a concern, fall applications are suggested.
Caution Do not allow spray to contact green stems, foliage, flowers, or cones because unacceptable injury may occur. Preharvest interval is 30 days. Avoid spray or drift outside the area. Do not mow or rake over treated area as dust created by mowing may drift onto sensitive crops or vegetation and damage crop foliage. No information on replant interval is available. Soil bioassay is suggested before planting hops in fields previously treated in the last 12 months if soil is tilled, or 18 months if soil is not tilled.
Site of action Group 14: protoporphyrinogen oxidase inhibitor
Chemical family N-phenylphthalimide derivative
fluridone (Brake On!)
Rate 0.19 to 0.40 lb ai/A (21to 43 fl oz/A).
Time Apply to dormant hops November through March in a 1 to 1.5-foot band to each side of the hop row for preemergence weed control. Rainfall following application will improve preemergence weed control.
Remarks Fluridone has preemergence control of many annual grass weeds, including Italian ryegrass and annual bluegrass. A single application per season up to 43 fl oz/A. Only apply fluridone products for up to two years in a row. When using rates of 21 to 32 fl oz/A, mix a second preemergence herbicide to improve weed control.
Caution The preharvest interval is 30 days. Replant interval is 3 months after treatment if clean soil is placed next to roots. Applying to newly planted hops can lead to plant death at 43 fl oz/A. Proper soil preparation and root-soil contact is needed before using fluridone in young hops.
Site of action Group 12: inhibition of phytoene desaturase
Chemical family Diphenyl heterocycles
glyphosate (several trade names)
Rate Consult labels
Time Apply to actively growing weeds.
Remarks Glyphosate will injure and kill hops, so avoid all contact with hop foliage. Remove any sucker that may be growing in areas to be sprayed. Use a low-pressure, coarse spray to minimize drift within the hop yard. Glyphosate controls many perennial weeds if applied at the weed growth stage stated on the label.
Caution Do not allow spray to contact green hop stems or foliage. Any crop receiving spray will be killed. Preharvest interval is 14 days.
Site of action Group 9: inhibits EPSP synthase
Chemical family glycine derivative
glufosinate (Rely 280)
Rate 0.58 to 1 lb ai/A (32-55 fl oz)
Time Apply as a directed basal spray to the lower 18 inches of a hop bine at least 8 feet tall.
Remarks Glufosinate may be applied with a hood to reduce drift to susceptible vegetation. Contact of glufosinate with green stems may cause injury and severe damage if bines are at 6 ft or less. Direct the spray to the lowest portion of the bines to reduce damage. Adding adjuvants like crop oil concentrate or methylated seed oil will improve control efficacy. Higher rates are recommended for improved weed control but are not needed if they are only targeted at hop foliage.
Caution The rates listed on the label are for treated acres. Do not concentrate rate into spray band. Application higher than 55 fl oz/A will damage bines and may result in illegal residues. Do not spray over the top of hop plants. Plants that were transplanted at 24 months or less, or have low vigor, are more sensitive to herbicide. The preharvest interval is 25 days.
Site of action Group 10: glutamine synthesis inhibitors
Chemical family phosphinic acids
indaziflam (Alion)
Rate 0.045 to 0.065 lb ai/A (3.5 to 5 fl oz/A product). Use the lower rates on soils with less than 1% organic matter content. Do not use on sand soils. Lower (3.5 fl oz/A) rates are preferred for crop safety.
Time Apply preemergence to weeds when hops are dormant. Fall applications are less likely to cause injury to the crop.
Remarks Controls numerous annual grass weeds and broadleaf weeds when applied prior to emergence. Can be applied as an early spring dormant application and/or as a fall dormant application after hop harvest. Do not apply more than two applications for a total of 7 to 10 fl oz/in a 12-month period depending on soil organic matter. Only apply to hop vines where the soil has completely settled around the vines and there are no open roots. Apply in a minimum of a 2 ft band on each side of the hop row. Applications made closer to spring may cause temporary growth stunting to hops. If early crop vigor is a concern, fall applications are suggested.
Caution Use only on hops that have been established at least one year. Do not use on soils with greater than 20% gravel content. Early spring dormant application can be made to hop shoots that are in the bud stage up to 2 inches tall. Do not allow spray to contact green stems, foliage, flowers, or cones or unacceptable injury may occur. Indaziflam is a soil-persistent product, so use-history may affect hop replanting.
Site of action Group 29: inhibits cellulose biosynthesis
Chemical family Alkylazine
isoxaben (Trellis SC)
Supplemental label
Rate 0.495 to 1 lb ai/A (16 to 31 fl oz/A product)
Time Apply preemergence to weeds when hops are dormant or in early bud stage of growth, in fall to early spring, to debris-free soil surface. Incorporate with 0.5 inch water within 21 days after application.
Remarks Identify weeds and adjust rates according to charts listed on label. Trellis SC performance is improved when application is banded to each side of the planting row before crop emergence. At least 20 GPA is recommended.
Caution Can be used on newly planted hops that the soil has have been settled by packing or rainfall. Soil cracks may cause plant injury. Do not apply through any type of irrigation system. Do not apply isoxaben to hops grown in commercial production nurseries.
Site of action Group 29: inhibits cellulose synthesis
Chemical family Benzamide
norflurazon (Solicam DF)
Rate 2 to 4 lb ai/A (2.5 to 5 lb/A Solicam DF), depending on soil texture
Time May be applied immediately after planting new hops. On established fields, apply to soil surface in fall after hop yards have been worked for the last time, or within 1 week after stringing in the spring.
Remarks Use lower rate on coarse soils and higher rate on fine soils. Note recropping interval on label is 12 months. Preharvest interval is 60 days. If planting a cover crop between hop rows, be aware of possible injury to small grains or direct applications to hop rows only. Lower rates must be used in coarse soils.
Site of action Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family Pyridazinone
paraquat (Gramoxone SL 3.0 and other trade names)
For use in Idaho, Oregon, and Washington only
Rate 0.5 lb ai/A in at least 10 gal/A water. Add nonionic surfactant or crop oil concentrate to spray mix.
Time For control of winter annuals, apply before hops begin to grow in spring. Apply after hop vines are at least 6 ft tall; direct spray to basal 2 ft of plants.
Remarks Direct spray around base and in interspaces of hops. Re-treatment or spot treatment may be necessary. Dust from treated areas that contain herbicide may move into hop cones.
Caution Restricted use pesticide due to acute toxicity for retail sale to and use only by certified applicators - not to be used by uncertified persons working under the supervision of a certified applicator. Do not let spray contact green portions of plant, because injury may result. Do not exceed three applications per season. Preharvest interval is 14 days. Do not graze animals in treated hop yard. Hop vine refuse and silage may be fed to livestock. Follow all safety precautions on label.
Site of action Group 22: photosystem I electron diversion
Chemical family Bipyridilium
pelargonic acid (Scythe)
Rate Apply in a total water volume of 75 to 200 gal per acre. Apply as a 3-5% (v/v) solution on young, small annual weeds and 5-7% (v/v) solution on perennial herbaceous weeds or annual weeds over 6 inches tall. For difficult to control weeds and maximum vegetation control use 7-10% (v/v).
Time Apply before hops emerge to control winter annual or early emerged weeds. Apply after hop emergence, but don't allow spray to contact emerged hops. Small weeds are easier to control than larger weeds. Warm weather promotes rapid activity on plants.
Remarks Apply as a spot treatment or as a directed and shielded spray avoiding contact with all desirable vegetation. Contact of spray or spray drift with emerged vegetation will result in damage. Repeat applications are required to control new weeds emerging from seed or underground vegetative parts. Broadleaf weeds are generally controlled better than grass weeds. Repeated use may select for grasses.
Caution Pelargonic acid is a nonselective herbicide. Any spray contacting desirable vegetation will likely result in damage.
Site of action Group 0 unknown. Disrupts cell membranes causing leakage from the cells and rapid wilting.
Chemical family Carboxylic acid
pendimethalin (Drexel Aquapen, Prowl H2O, Satellite Hydrocap)
Rate 1 to 4 lb ai/A (1.1 to 4.2 quarts/A product), depending on soil texture
Time Apply prior to target weed emergence when hops are dormant or in vegetative stages of growth. Apply the spray directly to the ground beneath the vines and/or in areas between rows with ground equipment. Apply in a single application or sequential applications with an interval of 30 days or more.
Remarks Controls many annual grass weeds and certain broadleaf weeds when applied prior to weed emergence. Use lower rate on coarse soils and higher rate on fine soils. Do not exceed a maximum total of 4.2 quarts/A per year. Preharvest interval is 90 days. Note recropping interval on label depending on application timing and rainfall. If planting a cover crop between hop rows, be aware of possible injury to small grains or direct applications to hop rows only.
Caution Do not apply over the top of vines with leaves or cones. Contact with hop foliage or cones by spray mixture may cause injury.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Dinitroaniline
trifluralin (Treflan and other trade names)
Rate 0.5 to 0.75 lb ai/A
Time Apply and incorporate when crop is dormant.
Remarks Use lower rate on coarse soils, higher rate on fine soils. Must be incorporated 1 to 2 inches with equipment that ensures soil mixing without injuring hop crowns. This treatment will not control mustards, prickly lettuce, horseweed (marestail), salsify, or nightshades.
Caution Do not spray over hop crowns. Take care that incorporation equipment does not injure hop crown buds that are needed to initiate hop bines. Disking operations that move additional treated soil onto the hop crown may delay emergence. Avoid exposing untreated soil when ditching for furrow irrigation.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Dinitroaniline
Certain Annual and Perennial Broadleaf Weeds
2,4-D + flumioxazin (Panther D)
Rate 0.5 lb ae/A 2,4-D + 0.0325 lb ai/A flumioxazin (1 pint/A product)
Time Make directed applications to row middles. Apply 1 pint/A each application, 30-day treatment interval.
Remarks Do not apply more than 1 pint/A in a single application. Do not apply more than 3 pints/A during a cropping season. Do not add an adjuvant. Controls numerous broadleaf weeds. Preharvest interval is 30 days.
Caution Do not allow spray to contact green stems, foliage, flowers, or cones because unacceptable injury may occur. Avoid spray or drift outside the area. Do not mow or rake over treated area as dust created by mowing may drift onto sensitive crops or vegetation and damage crop foliage.
Site of action (2,4-D) Group 4: synthetic auxin; (flumioxazin) Group 14: protoporphyrinogen oxidase inhibitor
Chemical family (2,4-D) Phenoxy acetic acid; (flumioxazin) N-phenylphthalimide derivative
2,4-D (several trade names)
Rate 0.48 lb ae/A (1 pint/A product)
Time Apply when annual broadleaf weeds are small.
Remarks Controls susceptible broadleaf weeds. Make directed applications to the row middles. Make up to three applications with at least 30 days between treatments.
Caution Avoid contact with new hop foliage and apical buds. Do not exceed 1.43 lb ae/A (3 pints product/A) per year crop cycle. Preharvest interval is 28 days. Avoid spray drift outside the target area.
Site of action Group 4: synthetic auxin
Chemical family Phenoxy acetic acid
bicyclopyrone (Optogen)
Rate 0.045 lb ai/A (3.5 fl oz/A product)
Time Apply to hops that are at least 6 feet tall.
Remarks Apply using shielded sprayers or hooded sprayers to control emerged and actively growing broadleaf weeds within or between the rows of the crop. Apply in at least 20 gal of spray solution. A single application per acre per season. Use a quality crop oil concentrate at 1% v/v. Controls only susceptible broadleaf weeds and grasses less than 2 inches tall or across. Do not apply within 30 days of harvest.
Caution Do not let spray contact growing points of plant, because injury may result. Do not apply to weak or low vigorous plants as it may cause serious injury. Do not exceed 0.045 lb ai/A (3.5 fl oz/A product) per season.
Site of action Group 27: inhibits 4-hydroxyphenyl-pyruvate dioxygenase (HPPD) enzyme
Chemical family Triketone
carfentrazone (Aim EC)
Rate 0.03 lb ai/A (2 fl oz/A product)
Time Apply to emerged weeds up to 4 inches tall.
Remarks Apply using shielded sprayers or hooded sprayers to control emerged and actively growing broadleaf weeds within or between the rows of the crop. Apply in at least 20 gal of spray solution. Allow 14 days between treatments. Use a nonionic surfactant with at least 80% ai at 2 pints/100 gal of spray solution or a quality crop oil concentrate at recommended rates. Controls only susceptible broadleaf weeds less than 4 inches tall or across. Do not apply within 7 days of harvest.
Caution Do not let spray contact green portions of plant, because injury may result. Do not exceed 0.119 lb ai/A (7.6 fl oz/A product) per season. Avoid spray or drift outside the area.
Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor
Chemical family Triazolinone
clopyralid (Stinger, Spur)
Rate 0.125 to 0.25 lb ae/A (0.33 to 0.67 pint/A product)
Time Apply after training when the growing points of the hop plants are above the spray zone.
Remarks Special local needs labels ID-040011, OR-040038, and WA-040008 for Stinger HL. Clopyralid has a narrow spectrum of weeds controlled and controls many weeds in the sunflower (e.g., Canada thistle, marestail), legume (e.g., clover), and smartweed families. Hops may show some transient, minor leaf cupping where the spray contacts the lower leaves and suckers on treated plants. Test within a small area before treating the entire hop yard. The grower assumes all risk of crop injury, yield reduction, and crop loss. If a second application is required, the re-treatment interval is 21 days. In Oregon, a sponge wiper application at 2 % v/v is permitted for spot treatment.
Caution Do not apply broadcast more than twice per crop per year. Do not exceed 0.25 lb ae/A per year. Preharvest interval is 30 days. Do not compost treated vegetation if compost will be used on sensitive species. Crop injury is expected if an over-application is made, often associated with spot-treatments using a back-pack sprayer.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
pyraflufen (Venue)
Rate 0.0040 to 0.0053 lb ai/A (3 to 4 fl oz/A)
Time Apply a minimum of 20 GPA for listed broadleaf weeds and sucker control. Direct applications to the basal 2 ft of vines or trained bines that are at least 6 ft tall.
Remarks Apply in at least 20 gal/A water. Higher water volumes are recommended for difficult to control weeds. Add crop oil concentrate to spray mix at 1% to 2% v/v.
Caution Do not apply more than two times per season. Allow 30 days between applications. Preharvest interval is 30 days. Follow all safety precautions on the label.
Site of action Group 14: protoporphyrinogen oxidase (PPO) inhibitor
Chemical family Phenylpyrazole