Hoary Alyssum is dangerous to horses, whether it is growing green in their pasture, or is included in dry baled hay.
Check out the links below for more identifying information and warning signs of toxin ingestion in horses.
The plant
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photo © Robert Garner, PBase Gallery
Links to Hoary Alyssum photos and information
- Hoary Alyssum: Toxicity to Horses, Forage Quality, and Control
- Discusses the possible toxicity of the weed hoary alyssum to horses, and clinical signs of toxicity. Includes information on forage quality and palatability of hoary alyssum and its biology and control. For those who own or keep horses, and for hay producers.
- Hoary Allyssum
- Hoary Alyssum / Berteroa incana / Tall Whitetop
Native to southeastern Europe and southwestern Asia
Noxious biennial (rarely perennial)
Annual to short-lived perennial
In the Mustard Family
Grows to 0.7 metres tall - Hoary Alyssum in Hay, Pasture and Forage
- Hoary alyssum (Figures 1, 2 and 3) is a weed common to Minnesota, the surrounding states, and Canada. It is particularly adapted to dry conditions such as occur on sandy or gravely soils. Hoary alyssum is a member of the mustard family and is perennial in its growth habit. Hoary alyssum tends to increase in forages following drought or The grey-green leaf of hoary alyssum.winterkill, regardless of the soil type of the field.
- Hoary Alyssum in Pasture and Hay Fields in Southwest Michigan
- Farmers and horse owners should be on the lookout for hoary alyssum, a weed species that has been found in a few hay fields in southwest Michigan which can be poisonous to horses. University of Minnesota Researchers reported that the ingestion of hay that contains a high level of hoary alyssum can cause horses to experience depression and cause a swelling of the lower legs. Fever and short term diarrhea also can accompany ingestion of the plant. Clinical signs normally subside within 2-4 days after the horses are removed from the alyssum source. In severe cases, foundering with stiffness in joints has been observed.
- Hoary Alyssum - Stevens County Noxious Weed Control Board
- Key identifying traits
* Flowers are white with 4 petals, deeply divided
* Usually only branched at the top of the plant
* Leaves are alternate, blades are simple
* Fruit is oblong, with two compartments containing 2 to 6 seeds
* Seeds grow close to stem, are round to oblong, narrowly winged, grayish-brown and rough - Ontario Weeds: Hoary alyssum
- It is distinguished from other mustards with rounded seedpods by its stalkless, non-clasping stem leaves with smooth (entire) margins, the dense star-shaped hairs that give the whole plant a hoary appearance, and the broad septum (membranous partition) in the oval, hoary seedpods which are held erect and very close to the stem.
- Toxic Weed Hoary Alyssum Found in Drought-Affected Pastures
- News and veterinarian-approved articles on equine health care from The Horse magazine.
The 2007 growing season's drought conditions are causing challenges for anyone who handles plants or animals. Horse owners are no exception, and to a list of concerns including a shortage of hay and lack of pasture growth they need to add awareness of hoary alyssum, a weed that is poisonous to horses. Hoary alyssum is found across the northeastern and north central United States and Canada. - Beware Of Hoary Alyssum In Horse Hay | toxic weeds in horse hay
- Georgia horse owners are urged to check alfalfa hay for a toxic weed and to consult with their veterinarians if their animals get sick. Tommy Irvin, the state's ag commissioner, says the weed has been found in some alfalfa from the Upper Midwest.
photo © University of Wisconsin
Is your horse at risk?
Clinical signs: Horses experience depression and swelling of the lower legs, 12 to 24 hours following ingestion of hoary alyssum in hay or on pasture. A fever and occasionally short term diarrhea have also been observed. These clinical signs normally subside 2 to 4 days following removal of the alyssum source. In more severe cases, an apparent founder with a stiffness of joints and reluctance of the animal to move has been observed. Recovery of animals with founder may take several additional days. In very rare cases, circumstantial evidence exists associating the plant with the death of a few horses. (source in links)
Inspect your hay and pastures regularly.
Learn the early warning signs of a reaction to a toxin in horses, such as depression, swelling in legs, diarrhea and fever.
Treat affected horses immediately to minimize the long-term effects of poisoning as much as possible.
photo © Government of British Columbia
Removal and control.
Pastures should be inspected regularly and the plants pulled up by the roots and destroyed so that the seeds are not dispersed.
As with any weed control program, proper pasture and hay management is the first consideration. This includes annual fertilization of pastures, seeding adapted species, and controlled grazing to avoid overstressing desirable forages. For hayfields, proper soil testing and seeding to insure adequate forage stands that are vigorously growing and competitive will help to prevent high levels of alyssum developing. If herbicides must be used, the most effective in pure alfalfa are products applied to dormant stands or following first cutting. For grass pastures, of the various broadleaf herbicides available, the most economical approach would be to apply 2,4-D in the spring or fall to suppress hoary alyssum. (source in links)
More information on controlling the spread of this dangerous weed can be found at the links above.
photo © Michigan State University Extension
Anything to add?
Take a moment to leave a comment on this lens.
AllHorses wrote...
There are many other plants and trees that are toxic to horses, and some are very common! Many sites offer help identifying these trees and plants. This page has a good reference list for starters: http://ohioline.osu.edu/b762/b762_24.html
Posted July 18, 2008
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