Using Livestock to Manage Invasive Weeds K. George Beck Bioag Sciences & Pest Mgmt Colorado State University

Basic Principles Using Grazing Animals for Weed Mgmt 1) Must be available1) Must be available 2) Livestock control/management:2) Livestock control/management: –must be able to adjust grazing pressure fencing, herdingfencing, herding –weed growth stage or time of year may be important for adequate control may need to keep off other times of yearmay need to keep off other times of year

Basic Principles Using Grazing Animals for Weed Mgmt 3) Direct weed control v. pasture conditioning:3) Direct weed control v. pasture conditioning: –direct damage by consuming weeds –indirect control by making pasture more competitive and “resistant” to invasion e.g. stimulating grass growth with proper grazing managemente.g. stimulating grass growth with proper grazing management strongly influenced by livestock class and interactions between livestock class and pasture speciesstrongly influenced by livestock class and interactions between livestock class and pasture species

Basic Principles Using Grazing Animals for Weed Mgmt 4) Livestock classes & grazing selection pressure:4) Livestock classes & grazing selection pressure: –Graze with one class may create problems feeding preference for various plant speciesfeeding preference for various plant species –e.g. cattle v. goats or sheep for leafy spurge changing livestock class can change feeding selection pressurechanging livestock class can change feeding selection pressure –combining livestock classes may better control weeds and condition pasture graze sheep or goats in leafy spurge infested pasture before cattlegraze sheep or goats in leafy spurge infested pasture before cattle

Basic Principles Using Grazing Animals for Weed Mgmt 5) Integrated weed management:5) Integrated weed management: –increased selection pressure on weed populations increased number of weed control methodsincreased number of weed control methods increased time of stress on weedsincreased time of stress on weeds –potential for synergisms

Basic Principles Using Grazing Animals for Weed Mgmt Sustainability:Sustainability: –proper use of grazing animals for weed control could enhance value & productivity of the world’s 7.9 billion acres of pasture –increased animal species on farm/ranch may improve economic opportunities –diverse weed control selection pressures, potential for better control –reduced herbicide use

Integrated Management of Canada Thistle Flagler CDOW Wildlife Area:Flagler CDOW Wildlife Area: –Major complaints about area being source of Canada thistle for neighbors –CDOW in cooperation with local FFA began project to evaluate grazing with herbicides to decrease CT and improve plant community for wildlife Chose to graze in spring with cattleChose to graze in spring with cattle Spray area in fall with herbicidesSpray area in fall with herbicides

Integrated Management of Canada Thistle Flagler CDOW Wildlife Area:Flagler CDOW Wildlife Area: –1990 CT dominant plant species in 300 acre areaCT dominant plant species in 300 acre area 75% cover75% cover –Integrated mgmt system: 1990, spring applied 2,4-D amine 1 qt/A1990, spring applied 2,4-D amine 1 qt/A 1991, grazed 180 cow calf pairs 41 days1991, grazed 180 cow calf pairs 41 days –Applied Banvel + 2,4-D in fall; 0.75 qt + 4 fl oz/A 1992, grazed 180 cow calf pairs 48 days1992, grazed 180 cow calf pairs 48 days –Applied Banvel + 2,4-D in fall; 0.75 qt + 4 fl oz/A

Integrated Management of Canada Thistle Flagler CDOW Wildlife Area:Flagler CDOW Wildlife Area: –Original goal was to decrease CT by 90% in 10 years However, achieved this goal in 3 years!However, achieved this goal in 3 years! –CT cover less than 8% –Increased native vegetation by 50% –Observations on cattle Trampled much of CT, dispersed litterTrampled much of CT, dispersed litter –Opened litter layer to expose to sunlight stimulated growth of desirable plants Consumed CT rosettesConsumed CT rosettes

Integrated Management of Leafy Spurge 2 experiments in North Dakota:2 experiments in North Dakota: –Lym, R.G., K.K. Sedivec, and D.R. Kirby Leafy spurge control with angora goats and herbicides. JRM 50:

Integrated Management of Leafy Spurge 2 experiments in North Dakota2 experiments in North Dakota –Repeated seasonal grazing 35 angora goats on 14 acres35 angora goats on 14 acres –1992 May 19 – Aug 24 (97 days) –1993 May 20 – Aug 18 (90 days) –1994 May 26 – Jul 7; Aug 1 – Aug 21 (63 days) With or without herbicidesWith or without herbicides –Tordon + 2,4-D 1 pt + 1 qt spring applied –Tordon + 2,4-D 1 qt + 1 qt fall applied –Spring herb + graze –Graze + fall herb –Graze alone –Herbicides alone

Repeated Seasonal Grazing T+2,4-D spr + grazing + grazing Graze + T+2,4-D fall T+2,4-D Spr only T+2,4-D Fall only Graze only Non-trt LS stems/0.25 m 2

Integrated Management of Leafy Spurge 2 experiments in North Dakota2 experiments in North Dakota –Rotational grazing w/1300 angora goats 7 paddocks grazed in succession7 paddocks grazed in succession –Each graze 3 times/yr 1992 –Each graze 2 times/yr 1993 and 1994 With or without herbicidesWith or without herbicides –Same treatments Goats concentrated on LS infestationsGoats concentrated on LS infestations –Grazed 2-3 hr morning; 2-3 hr late afternoon –Penned remainder of time

Rotational Grazing T+2,4-D spr + grazing + grazing Graze + Graze + T+2,4-D fall T+2,4-D Spr only T+2,4-D Fall only Graze only Non-trt LS stems/0.25 m 2

Experimental Design Three pastures used Three pastures used –One or two grazing events compared to no grazing for 4 years First grazing in April DK bolting inches tallFirst grazing in April DK bolting inches tall –Cattle grazed days Second grazing in May DK again inches tallSecond grazing in May DK again inches tall –Cattle grazed days 50% utilization of plant species50% utilization of plant species

Data Collection Data:Data: –Diffuse knapweed: Density, cover, height, seed production, tumbling over winterDensity, cover, height, seed production, tumbling over winter –Other species: CoverCover –Urophora spp larvae Larvae per flowering shootLarvae per flowering shoot

Diffuse Knapweed Seed Production Seeds/plant a ab b a b b a b c a b b

Diffuse Knapweed Shoots Remaining After Winter % shoots remaining b b a b a a c b a

Diffuse Knapweed Density April 2000 Shoots/m 2 b a a

Western Wheatgrass Cover April 2000 % cover a a b

Blue Grama Cover April 2000 % cover c b a a a a c b a

Diffuse Knapweed Pure Live Seed September 1999 PLS/m 2 a ab b

Cattle Graze Diffuse Knapweed Summary After 4 years of treatments:After 4 years of treatments: –56% decrease DK density non-grazed –Cover WWG 2.5X in non-grazed than grazed twice –Once or twice grazed 2.6X & 4.8X blue grama than non-grazed –Graze twice decreased seed production and PLS by 50% compared to non-grazed –Graze once or twice decreased tumbling over winter 9 to 37%

Leafy Spurge Grazing Research Varied sheep stocking intensity:Varied sheep stocking intensity: –Four sheep stocking rates 2, 4, 6, or 8 sheep per acre2, 4, 6, or 8 sheep per acre –Three grazing durations 10, 20, or 30 days10, 20, or 30 days With or without flea beetlesWith or without flea beetles –Flea beetles released at one end of plot Experimental controlsExperimental controls –No sheep grazing –With and without flea beetles Experiment conducted for 5 yearsExperiment conducted for 5 years

Leafy Spurge Grazing Research Summary 6 to 8 sheep/A graze 10 days for 5 yr6 to 8 sheep/A graze 10 days for 5 yr –Decreased leafy density 83-94% 8 sheep/A graze 10 days for 5 yr plus flea beetles8 sheep/A graze 10 days for 5 yr plus flea beetles –Decreased leafy spurge density to zero! 81% from sheep81% from sheep 19% from flea beetles19% from flea beetles Smooth brome and leafy spurge apparently primary competitorsSmooth brome and leafy spurge apparently primary competitors –SB also competed with western wheatgrass and Kentucky bluegrass

Leafy Spurge Density Sheep Grazing Only Days of grazing Sheep per acre Shoots/0.1 m 2

Smooth Brome Cover Sheep Grazing Only Days of grazing Sheep per acre % Cover

Leafy Spurge Density Sheep Grazing + Flea Beetle Herbivory Days of grazing Sheep per acre Shoots/0.1 m 2

Smooth Brome Cover Sheep Grazing + Flea Beetle Herbivory Days of grazing Sheep per acre % Cover

Western Wheatgrass Cover Sheep Grazing Only Days of grazing Sheep per acre % Cover

Kentucky Bluegrass Cover Sheep Grazing Only Days of grazing Sheep per acre % Cover

Colorado State University Weed Science