Regarding treatment of citrus: My friend Jody Johnson studied IMI (imidacloprid) treated maple trees and the impact on hive bees. Trees were being treated to control Asian Longhorn Beetle. By the way, Jody was very concerned about the potential harm that neonic treatments of maples might cause to bees. However, the facts are what they are:

> 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.

> Pesticide use is necessary for agriculture especially as we prepare to feed 9 billion people by the year 2050 (UN 5/12/24). Knowing how a pesticide translocates through a plant is useful to many, including botanists, APHIS (for the control of invasive species), entomologists, toxicologists, farmers, landscapers, and gardeners. The knowledge that IMI partitions to leaves mostly and less to flowers, that it distributes differently through plants depending on the species and that different injection methods cause different times in peak expression allows IMI to be used more efficiently to target insects.

> Norway and Sycamore maples and the willow were treated by APHIS to control the Asian Long Horned Beetle and could contribute to IMI levels in the pollen. Of the six types of pollen identified, red maple appeared to be a major pollen source during the week sampled given that the average red maple pollen content was 42%.

> 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 that is visited by honey bees. This link from treated red maple leaf to honey bee water source may be worthy of study.

Josephine Johnson. (2012)  The role of pesticides on honey bee health and hive maintenance with an emphasis on the neonicotinoid, imidacloprid. PhD Dissertation

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