Poisonous Plants (Martinson)

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Transcript of Poisonous Plants (Martinson)

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My Horse University and eXtension welcome you to this live Webcast.Plants Poisonousand Harmfulto Horses

Krishona Martinson, PhDEquine Extension SpecialistUniversity of Minnesota


Meet our presenters:

Krishona Martinson, PhDEquine Extension SpecialistUniversity of MinnesotaRoger Becker, PhDExtension Weed SpecialistUniversity of Minnesota2


Poisonous and Harmful Plants

Weed Control

Steps to Minimize Poisonous Plants3

IntroductionWeed a plant growing out of place

Invasive a weed capable of displacingexisting plants; This is a concern especiallywhen non-native weeds invade nativeecosystems.

Noxious on a State or County noxiousweed list


IntroductionWeeds are generally:

Less palatableLess nutritiousLower yieldingLess dependable as a forageInvasivePoisonousOn the noxious weed list


IntroductionMost toxicity is seen in the fall or during a drought when feed is short



Poisonous and Harmful Plants

Weed Control

Steps to Minimize Poisonous Plants7

Annuals 1 year to complete lifecycleFoxtailEastern Black NightshadeCommon CockleburWeed Seeds

Weed Control mowing and herbicide (if needed) in springAlways read and follow label directions


Foxtail (Seteria species)Annual

Causes physical trauma to the oral cavityand GI tract

Lip or tongue ulcers

Hay/pasture would be less than 10% foxtail

No selective herbicide options in grass pasture


Tickle Grass (Agrostis hyemalis)Embedded in horses mouth


Eastern Black Nightshade (Solanum ptychanthum)Annual

Ingestion of 0.5% to 1% bodyweight can be toxic

Affects GI tract

Clinical signs include colic

Broadleaf herbicides 2,4-D andor Dicamba


Common Cocklebur (Xanthium stumarium)AnnualStems are hairy, rough to the touch andReach 2-4 feet tall. The leaf surface ishairy and rough to the touch.The fruit is a 2-seeded bur covered withHooked spines. Burs easily becomeTangled in horse manes/tails.Cocklebur can be poisonous to allanimals, especially cattle and hogs.Can be controlled mechanically by hand-pulling and chemically by Stinger


Common Cocklebur (Xanthium stumarium)Cocklebur seedlings can be poisonousto all animals, especially cattle and hogs.

Can be controlled mechanically by hand-pulling and chemically by clopyralid.


Common Cocklebur (Xanthium stumarium)Conditions of poisoning occur most oftenin early spring (2-8 leaf stage)

0.25% body weight (2.5 pounds)

Affects liver

Clinical signs include colic and death


Mustards (Brassica species)Corn Cockle (agrostemma githago)Problems occur when horses ingest weedseeds in oats or sweet feedAffects GI tract and clinical signsinclude colicDont use field/bin run oats thathave not been cleaned


Biennials 2 years to complete lifecyclePoison HemlockWild Parsnip

Weed Control mowing (difficult in first year) and herbicide application (if needed) in first yearAlways read and follow label directions


Poison Hemlock (Cornium maculatum)Plants can reach heights of 2-7 feet tall

Stems have purplish spots

Leaves have a lacy appearance

Flowers are white and are shaped likeumbrellas


Poison Hemlock (Cornium maculatum)Found in wet sites or along streams

All parts of plant are very poisonous to allanimals when eaten fresh and in dried hay

Seeds are especially poisonous

Broadleaf herbicides Dicamba and/or 2,4-D


Wild Parsnip (Pastinaca sativa)Stem is somewhat hairy, grooved, and2-5 feet tall

Leaves are course, with saw-toothededges

Flowers are yellow, and arranged in anumbrella shape


Wild Parsnip (Pastinaca sativa)Found in fields and along roadsides,and occasionally in wet pastures

If pulling by hand, wear gloves andprotective clothing, as contact can causesevere blistering of the skin


Wild Parsnip (Pastinaca sativa)May contain furanocoumarins

Severe sunburn may occur throughskin contact, or in the blood vesselsdue to ingestion

Severe sunburn reduced if shadedfrom sunlight


Wild Parsnip (Pastinaca sativa)Broadleaf herbicides Dicambaand/or 2,4-D

Apply in first years growth or insecond years growth prior toflowering


Perennials Survives 3 or more yearsWaterhemlockHoary AlyssumWhite SnakerootButtercup (Tall)HorsetailBrakenfern

Weed Control mowing and herbicide application (if needed) in the fall (prior to flowering)Always read and follow label directions


Waterhemlock (Cicuta maculate)The small white flowers are borne inflat-topped, umbrella-like clusters atthe tips of stems and branches

Found in swampy areas and marshes,wet meadows and pastures, and alongstream banks and low roadsides


Waterhemlock (Cicuta maculate)Toxicity decreases through thegrowing season, and the toxicity ofabove-ground parts may be negligiblewhen dry

The roots are toxic at all times, evenwhen dry

Only 8 ounces will kill a horse


Waterhemlock (Cicuta maculate)Signs will develop within an hour, and includenervousness, and dilated pupils, muscle tremors,difficulty breathing, falling down andconvulsions

Death, may occur within 30 minutes of theonset of signs

Broadleaf herbicides: Dicamba and/or 2,4-D


Hoary Alyssum (Berteroa incana)Some horses experience depression, fever, and"stocking up," or swelling of the lower legs,12 to 24 hours following ingestion

These clinical signs normally subside 2 to4 days following removal

Hoary alyssum is mostly a concern in hay


Hoary Alyssum (Berteroa incana)Severe symptoms have been observedin horses ingesting hay containingmore than 30% hoary alyssum

Toxicity is variable and approximately45% of horses do not seem to react


Hoary Alyssum (Berteroa incana)Death has not been observed

Founder can be an issue with prolongedingestion or when stressed

Hay containing hoary alyssum shouldnot be fed to horses


White Snakeroot (Eupatorium rugosum)Plant reaches heights of 1 to 3 feettall

Leaves have toothed edges andflowers are white

Found only in shady areas

1 to 10 pounds of plant material isthe toxic dose


Buttercup (Ranunculus species)Affects lower GI tract and blisteringof lips and mouth

Clinical signs include colic

Mechanically controlled by handpulling. Chemically controlled byBanvel and MCPA


Field Horsetail (Equisetum arvense)Stems are tough and wiry, hollow and jointed

Found mostly on wet, sandy soil

It is poisonous to livestock when eaten in largequantities

Chemically controlled by Roundup (spot treatmentonly) or Triclopyr. Use caution when spraying near awater source.


Bracken Fern (Pteridium aquilinum)Plant grows 1 to 4 feet tall

Found in open pastures, woodlands andparticularly on acid soils (under pine trees)

Conditions of toxicosis occur if ingestionfor 30 or more days as 20% or more of thediet


Bracken Fern (Pteridium aquilinum)Affects brain and clinical signs include seizures

Mechanically controlled by frequentmowing. Chemically controlled by Ally(spot treatment only)



Control avoidance and species removal


Japanese Yew (Taxus cuspidata)Avoid introducing as landscapeornamentals in proximity to horses

Do not put clippings into pasture

Do not put yew wreathes on boxstall doors

Can cause death


Foxglove (Digitalis sp.)Rhododendron (Rhododendron sp.)Oleander (Nerium oleander)Avoid introducing foxglove, rhododendron, oleander as ornamentals in proximity to horses

Most are associated with overgrown or escaped landscapes

All can cause death37

Foxglove, Rhododendron & Oleander


Woody SpeciesChokecherryBlack WalnutMapleOak

Control avoidance and species removal


Chokecherry (Prunus virginiana)Chokecherry bark, leaves and seeds arepoisonous

Damaged leaves pose the greatest risk

Do not plant around horses

Cyanide is the toxin

Clinical signs include anxiety, breathingproblems, staggering, convulsions, collapseand death


Black Walnut (Juglans Nigra)Toxicosis includes using the shavings forbedding

Affects the vascular organs

Clinical signs include stocking up andfounder

Do not use dark shavings for bedding


Maple (Acer species)Ingestion of 1 to 3 pounds of wiltedleaves per 1,000 pound horse (Fall orSummer Storm)

Signs of toxicosis include colic and/orred/brown urine

Affects red blood cells and the liver


Oak (Quercus species)Most species of oaks can cause livestockpoisonings

Ingestion of LOTS of acorns with greenhull still attached

Affects the kidney (tannins)

Clinical signs include colic

Photo Credit: ACC-CTC 43

Grazing PrecautionsEndophyte Infected Fescue



Endophyte Infected FescueCan cause dry gangrene in feet and ears(restriction of blood flow), prolongedgestation, no/reduced milk production(agalactia)

Prevention: plant endophyte free fescue


Moldy Sweetclover (Melilotus species)Harvested for hay AND hay gets moldy.

An unknown mold converts the