(Photos by Kersti Muul)
We’ve received multiple inquiries about dead/dying bumblebees, particularly along California SW from The Junction to Morgan Junction. One of the people who noticed was local naturalist (and more) Kersti Muul, who provided the photos. We investigated a similar phenomenon a couple years ago, and recalled it wasn’t a case of spraying – as most assume when they happen onto the bees – but was traced to a particular kind of tree. Kersti, also an arborist, subsequently noted the trees in question are lindens:
Other parts of the nation/world have noted this phenomenon. Last fall, the New York Times wrote about researchers looking into it; they hadn’t entirely solved the mystery.
Not all bees are susceptible to this, as noted in this one-sheet from Oregon. The dead bees Kersti saw/collected are almost all yellow-faced bumblebees, of the species Bombus vosnesenskii. That Oregon document also reminds us that lindens are the trees that draw so many aphids, their secretions drip onto cars parked beneath them (it’s not the sap making those little spots, it’s the bugs). But you don’t want to spray those trees to kill the aphids – because that will kill other insects, such as bees, too.
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