Ammonium nonanoate (Axxe)
Rate A 10 to 13% volume to volume (v/v) dilution (13 to 16 fl oz per gal water) is recommended for most weed control situations and based on the results.
Time Apply to dry plant material, that will remain dry (no rain/no irrigation) for > 2 hr.
Remarks OMRI certified non-selective herbicide for commercial use. Do not allow spray to contact any green plant parts of desirable plants. Provides control and burndown suppression of annual and perennial broadleaf and grass weeds. Spore producing plants such as mosses and liverworts are also controlled.
Caution Causes serious eye irritation.
Site of action N/A
Chemical family N/A
asulam (Asulox)
Certain juniper and yew species only
Rate 3.34 lb ai/A
Time Apply postemergence treatment only when weeds are between the stages of early seedling and early seedhead formation.
Remarks Use at least 20 gal water. Do not use a surfactant. Controls crabgrass, barnyard grass, and horseweed (Conyza canadensis). Inhibits cell division or mitosis.
Caution Do not reapply within 12 months. Labeled for a limited number of ornamental species; consult label before use.
Site of action Group 18: inhibits DHP synthase step
Chemical family Carbamate
bentazon (Basagran T&O; Broadloom)
Do not use on sycamore or rhododendron
Rate 0.75 to 1 lb ai/A
Time Postemergence control of broadleaf weeds, Canada thistle, yellow nutsedge, and musk thistle.
Remarks Direct sprays toward actively growing weed foliage at weed size described on label. The label lists many species where over the top applications are permitted. Add 2 pints/A crop oil concentrate to enhance activity (see label). Two treatments 7 to 10 days apart may be required for Canada thistle or yellow nutsedge. Temperatures below 55°F, drought, or rain within 8 hours will reduce activity. Inhibits photosynthesis. May be tank-mixed with Tower, Segment and other herbicides.
Caution Do not apply within 1 year of harvest. Do not exceed 2 lb ai/A per season.
Site of action Group 6: photosystem II inhibitor
Chemical family Benzothiadiazole
clethodim (Envoy Plus)
Rate 0.068 to 0.24 lb ai/A (9 to 32 oz/A Envoy)
Time Apply postemergence to actively growing annual or perennial grasses as listed on label. 9 to 16 oz/A for annual grass control; 12 to 32 oz/A for perennial grass control.
Remarks For selective postemergence grass control. Consider environmental and plant growth conditions that affect leaf uptake. Surfactants (NIS or COC) and ammonium sulfate will enhance activity.
Caution Do not exceed 64 fl oz/A per season.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Cyclohexanedione
clopyralid (Lontrel, Cleanslate)
Rate Consult labels
Time Apply when weeds are small and actively growing. For Canada thistle, apply to rosette stage but before bud stage.
Remarks Apply over the top of labeled crops or as spot treatment to well-established plantings.
Caution Restricted-use herbicide in Washington. Do not exceed 1.3 pints/A per season. Avoid drift or treatment near susceptible crops or unlabeled and desirable plants.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
flazasulfuron (Mission)
Conifers only, Oregon and Washington only
Rate 0.033 to 0.045 lb ai/A (2.14 to 2.85 oz/A Mission)
Time Pre- and postemergence. Apply to broadleaf weeds and grasses less than 4 inches tall and prior to tillering of grasses.
Remarks May be applied over the top of conifers before spring bud break, or after new growth has sufficiently hardened. Use an adjuvant for postemergent applications. To control cottonwoods, wild carrot, and many grasses. Limited experience in the PNW. Many conifers are listed on the label. For those that are not, treat a small area of the field and evaluate crop safety for 6 weeks before treating the entire field.
Caution Do not apply the first year after seeding. Do not apply to conifer seedbeds. A 25-foot buffer must be maintained between the point of direct application and the closest downwind edge of sensitive terrestrial habitats (forested areas, riparian areas), freshwater habitats (lakes, rivers, sloughs), and estuarine/marine habitats.
Site of action Group 2: inhibition of the enzyme acetolactate synthase
Chemical family Sulfonylurea
fluazifop (Fusilade II)
Rate 0.25 to 0.375 lb ai/A (16 to 24 oz/A Fusilade II)
Time Apply to actively growing grasses or within 7 days after irrigation with 0.25% nonionic surfactant.
Remarks For selective postemergence grass control. Identify grasses and adjust rates for susceptibility and stage of growth as on label. Note lists of ornamentals and associated instructions regarding topical versus directed sprays. 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. Do not tank-mix with other pesticides. Inhibits fatty acid production, cell membranes, and new growth.
Caution Do not apply within 5 days of other pesticide treatments. Grazing is prohibited. Do not apply to grasses which have tillered, formed seed heads, or exceeded listed growth stages. Do not apply to trees, vines, or other listed crops that will be harvested for food/feed within 1 year after application. Maintain a minimum of 14 days between applications. Do not apply a total of more than 72 fl oz/A of Fusilade DX Herbicide per year (1.125 lb ai/A). Do not apply more than 24 fl oz of Fusilade DX Herbicide per acre per application (0.375 lb ai/A). Do not make more than 3 applications per year.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Aryloxyphenoxypropionate
glufosinate ammonium (Finale)
Spot or directed spray only
Rate 1 to 1.5 lb ai/A (4 to 6 quarts Finale/A)
Time Apply to thoroughly cover actively growing weeds.
Remarks Avoid all contact with desirable foliage and green bark.
Caution Using adjuvants may impair selectivity and increase potential injury to plants.
Site of action Group 10: glutamine synthase inhibitor
Chemical family Phosphinic acid
glyphosate (numerous products)
Rate Spray: consult the label
Time Apply as a directed spray toward the base of a tree when weeds are actively growing or moving sugars to roots.
Remarks Inhibits production of three amino acids and protein synthesis.
Caution Do not spray green bark, foliage, or root suckers. If repeat applications are necessary, do not exceed a total of 10.6 lb ai/A (10.6 quarts/A) per year.
Remarks Consult label about rate and time of application, especially perennial weeds.
Site of action Group 9: inhibits EPSP synthase
Chemical family None generally accepted
glyphosate (several products)
Rate Wiper: 33% solution
Time Mix 1 gal product to 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
paraquat (Gramoxone SL 2.0)
Established stock only
Rate Consult labels; formulations differ.
Time Apply as a directed or directed-shielded application when weeds are small (6 inches or less) and actively growing.
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. Avoid contact with stems or leaves of the crop. Acts as contact; absorbs energy produced by photosynthesis forming peroxides that disrupt living cells. Do not allow spray to contact green stems (except suckers), fruit or foliage. Use a shield or wrap plant when spraying around young trees or vines. For mature woody weeds, perennial weeds, late germinating weeds and green suckers, retreatment or spot treatment may be necessary.
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 ingest or inhale spray mist. Wear protective face shields, respirators, and clothing. Do not graze treated areas. Do not feed cover crops grown in treated areas to livestock.
Site of action Group 22: photosystem I electron diversion
Chemical family Bipyridilium
pelargonic acid (Scythe)
For nursery trees and shrubs
Rate 3% to 5% solution to control annual weeds, mosses, and cryptogams; 5 to 7% solution to burn down perennial herbaceous plants.
Time Apply to thoroughly wet foliage, either broadcast to non-crop area or before ornamental crop emerges; or spot treat and trim around ornamentals, trees, flower beds, paths, etc. Most effective when temperature is above 65°F.
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
sethoxydim (Segment)
Rate 0.28 to 0.47 lb ai/A (36 to 60 fl oz/A)
Time Apply at optimum growth stage listed on label, and rate recommended for targeted grass.
Remarks For selective postemergence grass control. Identify susceptible grasses. Results often are 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. Inhibits fatty acid production, cell membranes, and new growth.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Cyclohexanedione
sulfosulfuron (Certainty)
Rate 1.0 to 2.0 oz/A
Time Best results are obtained when target weeds are actively growing and not disturbed by mowing for at least 2 days before and 2 days after application.
Remarks Selective post-emerge weed control in warm-season turf and ornamentals
Caution Properties of this herbicide are associated with other herbicides that are sometimes detected in ground water. Use in permeable soil and where there is a shallow water table may result in ground water contamination. Highly toxic to non-target plants. Do not apply where surface water is present. Drift and runoff may be hazardous to neighboring plants.
Site of action Group 2
Chemical family Sulfonylurea