Frequently (and not so frequently) Asked Questions
BRIEF: Do you have any information on hoary allyssum?
QUESTION:
We recently had a horse die, the vet said it was a poisonous plant. I believe its
called "hoaryallysum", I don't have the correct spelling. We had some straw we
baled up and put down for bedding, that's the only thing different. The other
horses and mules didn't get sick. Would you know how much of this the horse
would have had to eat? We need to know what it looks like so we can get rid of
the straw bales that are bad. The horse that died from this had a very severe
cough, it seemed similar to when a human has dry heaves.
We are planning on plowing up the new seeding that had the straw on it, because
we don't know what we are looking for in a weed or plant. If you could send me
some information or someone to contact, I would be very grateful.
ANSWER:
Although hoary allyssum is poisonous to horses, it is reported to cause a high
fever, colic, and swelling of the limbs rather than a cough. This person may
have misunderstood her veterinarian. The poisonous plant may well be on the farm
but the horse might have died of allergic lung disease (heaves) from dust in the
straw or from pneumonia. The straw bales may be bad because they are dusty. If
you lack papers on hoary allyssum I can send copies to you campus mail.