Weed Control In Pastures

Weed Control in PasturesTroy D. CooperUSU ExtensionDuchesne County

IntroductionWeed control in pastures can be a verydifficult challenge.Plant species are unique in livestock grazingsystems.Focus on the plants that animals avoid eatingand those containing low nutritional value.Good weed control takes dedication and utilizationof several weed control methods.

Weed Control Options Cultural controls–Desirable plant growth–Proper grazing management–Irrigation, Fertilization–Competitive desirable plant species

Weed Control Options Mechanical Control– Physically disrupts weed growth Tillage Mowing Mulching Burning Chemical Control– The use of herbicides

Weed Control Options Biological control– Uses organisms to disrupt weedgrowth Insects Disease organisms Sheep Goats Cattle Or other large herbivores

Basic Principles ofChemical Weed Control Know your weeds Choose the rightherbicide Match equipment withneeds Calibrate your sprayer Spray at the proper time Read and FOLLOWlabel instructions

Weed Identification Plant Type– Broadleaf Dicots Net Vein– Grass and Grass-like Monocots Parallel veins Lance-like leaf

Weed Identification Life cycle– Annual Grow from seed, mature,and produce seed in oneyear or less.– Biennial 2 year life cycle. Grow fromseed and develop a rosette1st year. 2nd year mature,produce seed and die.

Weed Identification– Perennial Plants that live more than2 years. Most plantsmature and reproduce inthe first year and thenrepeat the vegetative,seed production andmaturity stages forseveral following years. Growing season– Cool Fall - Spring– Warm Spring - Fall

Lambsquarter, annual, rapidgrowth and high water use.Reproduced by seed.

Down brome, is an annual orwinter annual.Reproduced by seed.

Foxtail barley, perennial.Reproduces by seed.Common in wet alkalinesoils, meadows, and pastures.

Field bindweed is a perennialwhich has an extensive rootsystem. Seeds remain viable upto 50 years.

Russian knapweed, perennialspread by black deep growingroots. Forming dense colonies.

Musk thistle, biennial orsometimes a winter annual.Forms extremely densestands.

Scotch Thistle, Grows up to 8fttall. Flower is pale purple toviolet. Leaves are spiny edgedand form wings around thestalk.

Perennial pepperweed, perennial.Also referred to as tall whitetop.Deep seated rootstock.

Leafy spurge, perennial. Plantcontains a milky juice. Seedcapsules explode projectingseeds as far as 15 feet.

Purple loosestrife, is a prolificseed producer and has a perennialroot system. Each plant canproduce 2 million seeds.

Common burdock is a biennial,producing a rosette of large,thickly hairy leaves the first yearand an erect, much branched,coarse stem 3 -10 feet tall thesecond year.

Canada thistle is a colonyforming perennial from deepand extensive horizontalroots. Flowers are purple.Flowering occurs during Junethrough August.

Common cocklebur, an annual2-4 feet tall with the stem erect,branches ridged, potted andvery rough. The burs are irritatingboth to humans and animals.

Curly dock is a robust tap-rooted perennial growing2-5 feet tall. Inflorescences and even entire plantturns reddish-brown at maturity.

Hoary cress is a deep rootedperennial up to 2 feet tall.Sometimes called whitetop.

Kochia is an annual, 1-6feet tall, stems muchbranched, round, slender,usually soft-hairy, butoccasionally smooth, oftenred-tinged. Sometimescontains high nitratelevels and can be toxic.

Curlycup gumweed orrosinweed, biennial orshort-lived perennial.Reproduces by seeds andgrows 1 – 3 feet tall.

Herbicide labels Before using a herbicide check andread the label carefully. Each of the recommended herbicideshas benefits and risks associated withits use. Reference to commercial products ortrade names is made with theunderstanding that no discrimination isintended and no endorsement byCooperative Extension is implied.

2,4-DSeveral productsRate: 0.71 to 2 lb ae/ATime: Spray when annual weeds are young, succulent,and actively growing. Treat perennial weeds at thespecific growth stage(s) described on the label.Remarks: Controls many annual, biennial, and perennialbroadleaf weeds in rangeland and grass pastures. Alsocontrols certain brushy species. Deep-rooted perennialweeds and woody plants usually require repeatedapplications for maximum control. See label for rates forvarious weed species and for proper application timing.

2,4-DCaution: Do not apply if spray drift may contactnearby crops or desirable plants or contaminatewater for irrigation or domestic use.Do not graze meat animals within 3 days ofslaughter.Do not graze dairy animals within 7 days afterapplication.Do not cut hay within 30 days after application.Do not use on bentgrass, alfalfa, clover or otherlegumes, or on newly seeded pasture. When grassseed production is desired do not apply after headingbegins or when grass is in the boot to milk stage.Kills legumes.

dicambaBanvel, Vanquish, or Clarity; Rate: 0.25 to 2 lb ae/ATiming: Apply after weeds emerge. Treat annuals whensmall and actively growing. See label for proper timingand rates on perennials.Remarks: Controls many annual, biennial, and perennialbroadleaf weeds and many woody brush and vinespecies. Rate depends on weed species and growthstage at time of treatment. Can be applied using water,oil—water emulsions, or sprayable fluid fertilizer as thecarrier. May also be applied as a cut-surface treatmentto control unwanted trees or to prevent sprouts on cuttrees.

dicambaCaution: No waiting period between treatment andgrazing for nonlactating animals (see label for timingrestrictions on dairy animals). Meat animals must beremoved from treated areas 30 days before slaughter.Rates over 2 Ib ai/A may temporarily injure many grassspecies. Newly seeded grasses (see label) may beinjured at rates exceeding 0.75 Ib ai/A. Do not exceed8 Ib ai/A per season. Kills legumes.

glyphosateRate 0.1875 to 3.75 lb ae/ATime: Annual weeds are best controlled when small andactively growing. Apply to actively growing perennialweeds at or beyond full flower. Results are best if appliedin late summer or fall after seed forms. Fall treatmentsmust be before a killing frost.

glyphosateRemarks: Controls many annual and perennial weedspecies before renovating pastures. Rates depend onweed species, stage of growth, and density. Repeattreatments may be necessary to control weedsregenerating from underground parts or seed. May alsobe applied as a spot treatment or by wiper application toestablished pastures, but no more than 0.1 of any acreshould be treated at one time. Further applications maybe made to the same area at 30-day intervals.

· glyphosateCaution: A nonselective herbicide that kills forage plantscontacted. Total of all treatments must not exceed8 lb ai/A per year. Remove domestic livestock beforeapplication. Wait 8 weeks after broadcast applicationand 14 days after spot or wiper application beforegrazing or harvesting. Some glyphosate products ifapplication is 2 qts/A or less no waiting period betweentreatment and feeding or livestock grazing is required.Check label for specifics.

clopyralid 2,4-DCurtailRate: 2 to 4 quarts product/ATime: Apply when weeds are young and activelygrowing.Remarks: Use 2 quarts on light to moderate infestationsof Canada thistle and knapweeds (spotted and diffuse)in good growing conditions. Use 3 quarts for denseinfestations or under poor growing conditions. OnRussian knapweed, use 3 to 4 quarts.

CurtailCaution: Do not plant grasses for 30 days afterapplication. Do not use on newly seeded grass areasuntil grass is well established. Do not use on bentgrass.Do not spray pastures containing desirable forbs,especially legumes, unless injury can be tolerated.Do not use hay or straw from treated area for compostingor mulching on susceptible broadleaf crops. Do not grazedairy cattle in treated area for 14 days after application.Remove meat animals from area 7 days before slaughterif pasture was treated less than 2 weeks earlier. Do notcut for hay within 30 days after application. Do not usestraw or manure from treated areas for compost or mulch.

metsulfuronEscort, Ally, or CimarronRate: 0.33 to 2 oz product/A Escort0.1 to 0.4 oz product/A Ally0.1 to 1 oz product/A CimarronTime: Apply postemergence to actively growing weeds.Remarks: Controls a wide range of broadleaf weeds.For best results, use a nonionic or organosiliconesurfactant.

Escort, Ally XP, or Cimarron MaxCaution: Consult labels for each product; labels differsignificantly. Note restrictions on labels for use on fescue,timothy and ryegrass pastures. Note recroppingrestrictions on label.Ally XP, no grazing restrictions.Cimarron Max, Remove meat animals from treated area30 days prior to slaughter. No grazing restriction for nonlactating animals.

Other products labeled for pastures Tordon – restricted-use herbicideCrossbowSpikeMCPA – several em R&PTouchdown

Summary Provide proper nutrients and managementfor desired forage species. Identify weed problems and locations. Select which options or combination ofoptions you plan to use for control Perform the practices. Evaluate outcome

Credits University of Minnesota Extension, WeedControl in Pastures – Lesson 4 Colorado State University Extension, Range andPasture Weed Management by K.G. Beck Small Pasture Management Guide for Utah,Project Coordinator: James Barnhill, USUExtension Agent, Weber County. PNW Weeds – Pasture and Rangeland WeedControl Guide. Weeds of the West.

Weed control in pastures can be a very difficult challenge. Plant species are unique in livestock grazing systems. Focus on the plants that animals avoid eating and those containing low nutritional value. Good weed control takes dedication and utilization of several weed control methods. Introduction