honey bee threats

Is death camas a threat to honey bees?

A while back, beekeeper Bill Reynolds of Minnesota asked if I knew anything about the toxic effects of mountain death camas on honey bees. He was concerned because he recently found a large patch of it not 100 yards from his hives.

Although I found many references that claimed death camas is deadly to honey bees, I haven’t been able to find any information about how attracted honey bees are to it. It sounds like both the nectar and pollen are toxic, but whether honey bees like it or not is unclear.

The whole death camus issue is murky. First of all, the plant is known by several different scientific names, depending on who you ask: it may be referred to as Zigadenus venenosus, Zigadenus nuttallii, or Toxicoscordion venemosum. In addition, it bears a vast collection of common names including mountain death camas, grassy death camas, mystery grass, poison garlic, poison wild onion, poison camas, and hog potatoes.

Apparently bees leaving death camas flowers exhibit erratic flight. If this is the case, the poison acts quickly—maybe so quickly that a forager can’t get home to report her findings to nest mates? I don’t know. But a paper by Hitchcock (1959) reported that Osmia lignaria (orchard mason bees) fed death camas toxin were paralyzed then died. Similarly, both larvae and adult bees fed sugar water laced with death camas toxin were killed in 89% of the bee species tested.

Oddly enough, there is a specialist pollinator for mountain death camas, a species of ground-dwelling bee called Andrena astragali. Trepedino (1982) found that the scopae of this little bee contained primarily the pollen of mountain death camas, which was taken back to the nest and stored for the larvae. The adult bee, however, nectared on plants other than death camas for its own energy needs.

So there’s lots of interesting information out there, but none that answer the question. Has anyone ever seen honey bees foraging on death camas? Should Bill worry or not?


Mountain death camas growing in Minnesota. © Prairie Home Farm.

Mountain death camas growing in Minnesota. © Prairie Home Farm.

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  • Rusty,

    I emailed Marla Spivak (Ph.D Entomology University Minnesota) about the camas too. Her response was: “Yes, mountain death camas is toxic to bees. But likely it is not growing in sufficient density to be attractive to bees—I would not worry too much about it.” Marla didn’t have any additional information to add.

    Since taking the image above, I’ve only notice a fly working this flower on each of my walks into that area. I’ve not notice any unexplained deaths at the hive, so I guess at the moment the camas is not a problem, but one worth monitoring.


  • Very interesting. I’ve got loads of the blue camas on my place, and a few “albino” white plants that are not the poisonous variety. (but I’m not going to try eating them) A group from Oregon state that collect native plant seeds here have found only one Z. venenosus plant that I know of. I was not aware that they were toxic to honey bees too.

  • Rusty,

    I’ve read your info on moving a hive but you stated that actually moving is another subject and that’s what I need to know/see. I’m older and new to beekeeping. This year in Colorado we had more moisture and I finally got to put on a super. Problem is they are defensive and I can’t work in the garden so I need to move the hive. I’m not sure how to get the straps on. Could you give a little advice. Greatly appreciated. Great site and info.

    • Donna,

      It depends how far you are moving the hive, but for short distances I strap the whole thing together (top to bottom) with a ratcheting tie-down (the kind frequently used to secure loads in pickup trucks) and then tip the whole thing onto a furniture dolly or hand truck.

      If you don’t have all the equipment, you may have to move a box at a time, but this doesn’t allow you to lock up your bees. The aggressive/defensive phases usually don’t last very long, so maybe you could wait it out. Moving a hive is heavy work, so be careful.

  • I didn’t realize we started our hives last year right next to a large patch of Death Camas with white flowers. Our bees don’t touch them and they’re in full bloom right now. They don’t seem to be affected by them to date.