RE: And to this day, no one will even consider measuring the levels of contamination found in nectar and pollen after these injection treatments.

Jody Johnson did her PhD Thesis on the maples of NYC

Title of Dissertation: The role of pesticides on honey bee health and hive maintenance with an emphasis on the neonicotinoid, imidacloprid

This study was undertaken to determine how IMI translocates through a red maple tree when it is applied by either soil or trunk injection. To quantitate the degree to which honey bees are exposed to IMI in the nectar or pollen from injected trees, we monitored leaves, flowers, pollen, nectar, and foraging honey bees in treatment areas for IMI levels and six of its metabolites. The study locations were in New York City where IMI is being used by Animal and Plant Health Inspection Service (APHIS) to control the invasive Asian Longhorned Beetle

Two studies described here attempt to quantitate IMI’s presence in surface water and to track its movement through the vascular system of the red maple (Acer rubrum) to determine to what levels honey bees are exposed through water, pollen, and nectar. Of the 108 water samples collected, 9 samples ranged from 7-131ppb (LD50=280ppb), and 14 samples were at the limit of detection by ELISA assay. The red maple study revealed ranges of IMI in plant tissue of 0-53,300 ppb in leaves, 0-5440 ppb flowers, 0-32 ppb pollen, and 0 ppb in nectar, supporting evidence of predominantly xylem transport.

The results we found suggest that IMI is not a risk to honey bees through the pollen of red maples but the high concentration of IMI in red maple leaves may raise a different issue to honey bees. The concentrations of IMI at levels on the order of 103 ppb in leaves could be an exposure risk to honey bees if the concentrations were released from the leaves. One scenario for exposure is through the decomposition of leaves in pooled water 

Another scenario is that IMI released from decomposed leaves is taken up again by other plants like the common dandelion (Taraxacum officinale), the pollen of which is foraged by honey bees.

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