[Pollinator] Details of Virginia Linden Tree Bee Kill and insights on Bee Sampling

[Droege, Sam]

 All:
As Aimee code from Xerces mentioned previously there was a Linden tree
associated  kill event in Reston, VA

Table below documents the species involved (I did all the identifications)




Queen Worker Male Female Unknown  Total
Bombus bimaculatus 21 160 100 281
Bombus impatiens 26 134 160
Bombus griseocolis 5 62 47 114
Bombus perplexus 28 521 40 589
Bombus unkown  25 25
Xylocopa virginica  23 42 23
Apis mellifera 6 1 7
Megachile mendica 10 10
Megachile gemula 1 1

Andrena vicina
11 11
Andrena pruni 1 1
Andrena perplexa 5 5
Andrena barbara 6 6
Andrena species  2 2
Eucera rosae  1 1
Total  80 883 210 38 25 1278

Here is what we know:

   - 3 trees involved
   - *Tilia cordata *(note:  this species is not associated with Linden
   poisonings in Europe)
   - Trees were in parking area of a residential area of Reston, Virginia
   - At least 2 trees with noticeable soil injection points
   - Management company said they were treated in March and had been
   treated every year for about 6 years
   - Unclear what chemicals were involved or whether treatments changed or
   whether more trees were treated elsewhere
   - Company was advised by their lawyers to no longer speak to anyone
   - 3 people reported the kill but no kill was reported in previous years
   - Most of these bees were picked up on one day
   - 500 or so were picked up by State of Virginia for analysis and not
   available for species determination
   - Management company would not allow additional collections
   - Trees were not netted after kills were known
   - Note that only 6 *Apis *were found...despite much greater activity
   ...likely they took nectar back to hives, not clear if there was honey bee
   mortality at the hives
   - A chemical assay of bees and flowers will be made by the state
   - Pattern is very similar to those of Oregon Linden mortality
   events...and seems likely to involve neonic treatment

We are looking at followup studies to see if mortality continues in
subsequent years pending permissions

Note that the kill documented here is only part of the total kill

   - Birds were actively eating the dead and dying bees
   - Bees could have flown off and died
   - Small bees were not found...but were likely present
   - Mostly bees were collected from only 1 day, the tree would have been
   blooming several additional days

Who knew...

There were so many bumble bees in the area....this is good news from bad.
I think we often in our minds underestimate the true number of bees in an
area.  Here we are in average suburbia with lots of development and have
this many bumble bees at one place.  When sampling bees we never reach
anywhere this number under any circumstance I have seen.  Thus we have to
wonder how representative some of our low number samples might be, with the
notion that we need to probably err on higher capture rates in our studies
rather than lower.

sam

The earth has many keys,
Where melody is not
Is the unknown peninsula.
Beauty is nature's fact.

But witness for her land,
And witness for her sea,
The cricket is her utmost
Of elegy to me.

   - Emily Dickinson






-- 
*Why Did you Mow My Flowers? *
*- Bee*
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