Hi Sue --
>are alive with bees gathering what looks like dot size grains of
>yellow on the underside of the leaf only  and are packing the brood nest
with
 
If my memory serves me correctly several cottonwood like trees (Populus)
have resin that developes on the leaf or near where the leaf connects.
Bees collect this resin and make propolis from it.  If indeed the bees
are packing cells with this resin then for me this is news.  I feel that
more than likely they are getting nector from another souce.
 
 
Brett D. Bannon
Folsom, NM  USA
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