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Using Herbicides to Manage
Invasive Weeds
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Herbicide Development
Stimulus: realized chemical environment of plant easier to manipulate than climatic, edaphic, or biotic environments in which they grow
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Herbicide Classification Many Schemes
Degree of response among plants: selective controls some species in presence of others non-selective controls all species
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Herbicide Classification
Method of application: foliar applied soil applied broadcast entire area spot restricted area band
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Herbicide Classification
Length of soil persistence: persistent injure follow crop normal rotation residual injure/kill germinating weeds short time 1 growing season or less long residual control several growing seasons
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Herbicide Classification
Chemistry/herbicide family: inorganics organics
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Herbicide Classification
Organics: phenoxy-, benzoic-, pyridine-, quinolinecarboxylic acids sulfonylureas, imidazolinones, triazolopyrimidine triazines, substituted ureas, uracils thiocarbamates, halogenated acids dinitroanilines, carbamates, phosphoric amides aryloxyphenoxypropionates, cyclohexanediones nitrodiphenyl ethers those with no particular family
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Herbicide Classification
Plant related characteristics: systemic translocates throughout plant contact no translocation mode/mechanism of action
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Herbicide Classification
Mode/mechanism of action: amino acid biosynthesis inhibitors Escort, Amber, Plateau, Roundup auxin-like Tordon, Curtail, 2,4-D, Vanquish/Clarity photosynthetic inhibitors Velpar, Karmex, Krovar, Spike cell division inhibitors Treflan, Prowl lipid biosynthesis inhibitors Poast, Fusilade
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Herbicide Formulations
Form solutions: soluble liquids Tordon, Plateau, 2,4-D amine Form emulsions: emulsifiable concentrates 2,4-D ester, Treflan
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Herbicide Formulations
Form suspensions (need agitation): water dispersible granules Escort, Amber flowables Sencor wettable powders Karmex, Krovar Dry solids: pellets Spike
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Methods of Application
Broadcast: aerial or ground low volume liquid granules or pellets Spot treatment: typically by ground high or low volume liquid Band:
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Herbicide Application
Rule Number 1: Read and follow the label directions!! Rule Number 2: see Rule Number 1
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Factors Influencing Herbicide Performance
Plant factors: Weed ID Weed phenology/physiological status life cycle monocot v dicot location of meristems growth stage cuticle leaf number, shape, orientation, & pubescence metabolism Competition from desirable plants
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Factors Influencing Herbicide Performance
Herbicide factors: formulation volatility absorption dose placement retention use of adjuvant
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Factors Influencing Herbicide Performance
Climate: precipitation & relative humidity temperature wind light
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Factors Influencing Herbicide Performance
Edaphic (soil) factors: adsorption, degradation, leaching, volatility, availability for absorption texture organic matter pH moisture temperature
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Factors Influencing Herbicide Performance
Other factors: topography application efficiency sprayer calibration knowledge of operator Water Use clean water
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Commonly Used Herbicides
Rangeland & Non-crop
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2,4-D - Many Trade Names Auxin-like, systemic, selective
ester and amine formulations Short residual in soil average half-life 10 days Broadleaf herbicide many annual broadleaf weeds notably weak on kochia often tank-mixed High volatility
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Dicamba - Vanquish/Clarity/Overdrive
Auxin-like, systemic, selective Relatively short soil residual < 14 days good conditions metabolism low to medium leaching potential, weakly adsorbed Broadleaf herbicide many annuals, biennials, perennials thistles and knapweeds weak on toadflaxes & Russian knapweed Don’t use near water or trees/shrubs buffalograss sensitive to injury
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Picloram - Tordon 22K, Picloram 22K
Auxin-like, systemic, selective Residual herbicide average half-life 90 days high leach potential, weakly adsorbed Broadleaf herbicide thistles, knapweeds, leafy spurge, houndstongue, toadflaxes, bindweed, locoweed, larkspur, lupines … Grazon P+D is picloram + 2,4-D very weak kochia & some mustards Don’t use near water, trees/shrubs smoothbrome sensitive to injury
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Aminopyralid Milestone, Milestone VM, Forefront R&P
Auxin-like, systemic, selective Short residual average half-life 34.5 days in North America Lab studies show potential movement; limited movement in field Broadleaf herbicide - odd spectrum thistles, knapweeds, hawkweeds, oxeye daisy, dandelion, absinth wormwood … Forefront R&P is aminopyralid + 2,4-D Can spray to water’s edge Half-life in water 0.6 days Safe around some trees/shrubs
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Clopyralid Transline, Clopyralid 3
Auxin-like, systemic, selective Short residual average half-life 40 days moderate leaching, weakly adsorbed Broadleaf herbicide - odd spectrum thistles, knapweeds, hawkweeds, oxeye daisy, dandelion, locoweeds … Curtail is clopyralid + 2,4-D only control emerged weeds Don’t use around water Safe around trees/shrubs
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Metsulfuron – Escort/MSM 60/Cimarron Plus;
Amino acid biosynthesis inhibitor systemic, selective Moderate residual typical half-life 30 days persistence increases with soil pH Broadleaf herbicide perennial mustards, biennial thistles, arrowgrass, locoweed, halogeton, houndstongue, camelthorn, African rue … weak on toadflaxes, Canada thistle, diffuse knapweed must use a surfactant!!
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Chlorsulfuron – Telar/Chlorsulfuron 75 Cimarron Plus
Amino acid biosynthesis inhibitor systemic, selective Residual average half-life 40 days persistence increases with soil pH Broadleaf herbicide perennial mustards, Russian knapweed, Canada thistle RK, CT high rates and fall best must use surfactant!! Fall applications more injurious to some grass species
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Imazapic Plateau, Panoramic
Amino acid biosynthesis inhibitor systemic, selective Residual most “imis” persistent e.g. imazapyr 1-4 months Broadleaf and grass leafy spurge, bindweed, houndstongue, cheatgrass, foxtail barley … must use methylated seed oil!! Cool-season grass injury fall applications for leafy spurge
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Glyphosate - Roundup, Campaign, Rodeo, Aquamaster
Amino acid biosynthesis inhibitor systemic, non-selective Campaign is glyphosate + 2,4-D Rodeo is aquatic formulation Moderate persistence average half-life 47 days strongly adsorbed, no soil activity Broadleaf and grass many annuals, biennials, perennials Campaign good control perennial pepperweed
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Aminocyclopyrachlor Perspective, Method
Perspective - noncrop Telar + aminocylopyrachlor Method - noncrop aminocyclpyrachlor Amino-acid biosynthesis inhibitor + Auxin-like; systemic, selective Short to long residual Aminocylcopyrachlor half-life range days in North America Lab studies show potential movement; limited movement in field Broadleaf herbicide - odd spectrum thistles, knapweeds, leafy spurge, mustards (Telar) …
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