This is pretty interesting because, in deciduous trees, much of the imidacloprid does accumulate in foliage, but is then shed with leaf fall to be broken down by microbial activity.
Some Things to Think About Before Injecting
Hemlock woolly adelgid feeds in the xylem ray parenchyma cells. Parenchyma cells are the living tissues within the xylem. It is a network of radial and axial tissues that form a reticulated network. This allows you to begin to manage a number of trees efficiently.
Simply, start with a survey of high-value trees. High-value trees are those that provide ecological services or they may have value because of how old they are. Old-growth hemlock has been recorded as old as 600 and 900 years, it is our redwood of the east! Minimally trees that ought to be considered for treatment may simply be seed trees, those trees that will become the seed bank once HWA burns through the forest.