Bombus possibly killed by Golden Raintree nectar...?
This just came across my email from the MD IPM Weekly report.
Note however, that there may be possible confusion between the golden rain tree (Koelreuteria paniculata) and the golden chain tree (Laburnum). The later (according to Wikipedia) is highly toxic in all parts, while the former has edible seeds...in any case, the observations below bear repeating so that we can all keep watch for problems. I believe that in Maryland that
Koelreuteria paniculata is more common and I think of it as incredibly attractive to Megachile sculpturalis.
Juang-Horng ‘JC’ Chong, Ph.D., Clemson University, sent out an interesting inquiry about bees being
killed by a golden raintree. Here are his question/observations:
Did anyone ever observe a large number of dead bumblebees associated with goldenrain tree? A good friend,
who is also the executive director of a local botanical garden, informed me that the goldenrain tree/Chinese
flame tree (Koelreuteria bipinnata) in the garden was in full bloom and killing bees. Last Friday, we counted
about 48 dead bumblebees (species not identified) under the tree. At the time, hundreds of honeybees, bumblebees
and other native bees were visiting the flowers; only bumblebees were found dead. Ignorant of the effects
of goldenrain trees on bees and suspecting that the hive and bees might be poisoned before visiting the flowers,
I suggested to my friend to clean up the ground and see what happens next. The ground was cleared on Tuesday.
Dead bumblebees were found on the ground on Tuesday afternoon (20) and Wednesday (42). The trees have
never been treated with any insecticides, systemic or otherwise. I have not heard of a similar occurrence. I
cannot confirm if something similar is happening in the neighborhood because those may be the only two
goldenrain trees within a radius of 10 miles.
David Held, Auburn University, had this response:
What a cool observation. It is possible that the nectar of certain trees may have a narcotic or toxic effect on
bees, although the two references that I have don’t include goldenrain tree but Sophora spp. In many instances,
the toxic effect can be traced to yeasts associated with the nectar. I would guess that an intoxicated bee that
wasn’t poisoned outright would die secondarily from desiccation on a hot summer day.
Here are the bee references for your interest.
P.G. Kevan, D. Eisikowitch, S. Fowle, and K. Thomas. 1988. J. Apic. Res. 27(1): 26-29.
P.G. Clinch, T. Palmer-Jones, and I.W. Forster. 1972. N.Z. J Agric Res. 15:194-201. -alkaloids in the nectar
inducing a narcotic effect on bees.
Sam Droege sdroege@...
w 301-497-5840 h 301-390-7759 fax 301-497-5624
USGS Patuxent Wildlife Research Center
BARC-EAST, BLDG 308, RM 124 10300 Balt. Ave., Beltsville, MD 20705
As imperceptibly as grief
The summer lapsed away, -
Too imperceptible, at last,
To seem like perfidy.
A quietness distilled,
As twilight long begun,
Or Nature, spending with herself
The dusk drew earlier in,
The morning foreign shone, -
A courteous, yet harrowing grace,
As guest who would be gone.
And thus, without a wing,
Or service of a keel,
Our summer made her light escape
Into the beautiful.
- Emily Dickinson