2,4-D LV ester (several products)
Rate 1.9 to 7.6 lb ae/a, depending on target species
Time Apply when woody plants are in full leaf and actively growing.
Remarks Use higher rates if plants are stressed. Adding oil or wetting agents and/or using high carrier volumes may enhance control.
Caution Applications to stressed plants may reduce control. Do not allow spray to drift off target.
Site of action Group 4: synthetic auxin
Chemical family Phenoxy acetic acid
aminocyclopyrachlor (Method)
Rate 10-18 oz/a
Time Apply preemergence or postemergence when weeds are actively germinating or growing.
Remarks Do not apply where roots of woody plants extend unless injury or loss can be tolerated. The root zone can extend beyond the canopy. Even low rates can kill nontarget tree and shrub species. Sensitive trees include, but are not limited to, ponderosa pine, Douglas-fir, Norway spruce, white pine, aspen, Chinese tallow, cottonwood, honey locust, magnolia, poplar, redbud, silver maple, and willow. Individual plant treatments are allowed on sites transecting areas grazed by livestock.
Site of action Group 4 synthetic auxin
Chemical falurea (metsulfuron methyl)
dicamba (Banvel, Trooper, Rifle, or Clarity)
Rate 0.25 to 2 lb ai/a
Time Apply to actively growing vegetation.
Remarks Controls many annual and perennial broadleaf weed species as well as brush. Other herbicides often are combined and sold under a variety of trade names. Consult label for rates, times of application, use restrictions, and preparations for each of these proprietary mixtures.
Caution Do not use in areas where roots of desirable vegetation may extend.
Site of action Group 4: synthetic auxin
Chemical family Benzoic acid
fosamine (Krenite S)
Rate 6 to 24 lb ai/a
Time Apply in late summer or early fall before fall coloration.
Remarks Apply as a foliar spray to brush. Can be used in either air or ground equipment. Susceptible treated plants fail to refoliate the following spring. Total spray coverage is required.
Site of action Not well understood
Chemical family Organophosphorus
glyphosate
Rate 1.5 to 3.75 lb ae/a, depending on target species
Time Apply to foliage of actively growing woody plants.
Remarks Results are best if applied in late summer or fall after fruit forms. In arid areas, results are best if applied in spring to early summer when brush species have high moisture content.
Caution Control may be reduced if applied to stressed plants or after a fall frost.
Site of action Group 9: inhibits EPSP synthase
Chemical family None generally accepted
imazapyr (Arsenal, Arsenal Applicator Concentrate, or Chopper)
Rate 0.25 to 1.5 lb ai/a
Time Apply postemergence to weeds or brush.
Remarks Controls most annual and perennial grasses, broadleaf weeds, vines, brambles, and woody brush and tree species for forest management site preparation and release.
Caution Do not apply where chemical may contact roots of desirable trees or other plants.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Imidazolinone
metsulfuron (Escort XP)
Rate 0.6 to 1.2 oz ai/100 gal (1 to 2 oz/a)
Time Apply to brush when brush is fully leafed out until the beginning of fall leaf color.
Remarks Rate depends on species to be controlled. Adding a nonionic surfactant enhances activity. Complete coverage of all leaves and stems is required.
Caution Do not allow spray to drift to adjacent crops or other valuable plants or trees.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Sulfonylurea
picloram (Tordon)
Rate 0.125 to 1 lb ae/a
Time Apply to foliage of actively growing weeds and brush.
Remarks Picloram has soil residual activity. It is formulated in several mixtures, including combinations with 2,4-D.
Caution Most formulations are restricted-use herbicides. Follow all use restrictions and precautions on label.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
tebuthiuron (Spike 20P)
Rate 3.75 to 5 lb product/a, (broadcast), 1/8 to 3/8 oz product per 100 sq ft (individual shrub)
Time East of the Cascades, apply in fall; west of the Cascades, apply in spring.
Remarks Rate depends on species to be controlled. Requires rain to move into soil.
Caution Kills desirable trees, shrubs, and other vegetation with roots in the treated area. Apply only once per year.
Site of action Group 7: photosystem II inhibitor
Chemical family Substituted urea
triclopyr (Garlon 4 Ultra)
Rate 1 to 6 quarts/a, depending on weed species, maturity stage, and environmental conditions
Time Apply when woody plants and weeds are actively growing. The ester formulation may be used in the dormant season. See label for instructions.
Remarks Controls certain perennial broadleaf weeds and woody plants. If lower rates are used on hard-to-control species, they may resprout a year later.
Caution On range and pasture sites use no more than 2 qt/a. See label for grazing restrictions.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
triclopyr + 2,4-D (Crossbow)
Rate 1 quart to 4 gal product/a
Time Apply during warm weather when brush and weeds are actively growing.
Remarks Controls most species of unwanted woody plants as well as annual and perennial broadleaf weeds. Rates depend on weed species.
Caution Application during drought may have less-than-desired results. Use low spray pressure to minimize spray drift. Avoid contacting nearby susceptible crops or other desirable plants. Avoid contaminating water for irrigation or domestic use. Do not use or store near heat or open flame.
Site of action (both) Group 4: synthetic auxin
Chemical family (triclopyr) pyridine; (2,4-D) phenoxy acetic acid