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?