I should qualify my statement.
"Unfortunately this theory doesn't include tree or weed pollen?"
(A)"It is to do with the pollination method used by some" trees
(B)"Agricultural intensification has led to the decrease of the diversity of wild and domestic pollinators"
Weeds
Thanks for your interesting question @prydefoltz I hope this data clarifies my theory.
The use of weedkillers has changed the amount of weed pollen captive bees can access.
That would make sense with some trees ... but it is worth a try for sure ... I am think honey, lemon and ginger tea ... will hit the spot:)