Report for period ending 12/31/14 Work continued on our previously reported efforts to determine the level of imidacloprid in leaf tissue required to prevent ACP phloem feeding behaviors. This work involved both field studies and concurrent laboratory-based studies. In the field, trees of varying size classes were treated with the recommended rate of imidacloprid. At 2, 4, and 6 weeks post-treatment, leaf samples were collected and analyzed for imidacloprid concentration. The levels of imidacloprid detected in leaf tissue ranged from a low of 2.5 PPM (2,500 PPB) to a high of 12.3 PPM (12,300 PPB), varying with tree size and generally decreasing with increased time following application. However, in some field plots, ACP were observed feeding on treated plants 2-3 weeks following imidacloprid application. Tests of the ACP did not show any decline in susceptibility to imidacloprid where collected from trees with an average level of imidacloprid in leaves of 2-3 PPM (2,000-3,000 PPB). This was in direct contrast to previously published studies suggesting that 200-250 PPB (0.2PPM) is sufficient to control ACP. This finding was examined further in the laboratory by feeding ACP on citrus leaves with a known level of imidacloprid. Our work had previously focused on developing a system for obtaining leaves with a desired level of imidacloprid residues delivered systemically (not foliar application). Using the methods we developed, we fed adult APC on leaves containing 0, 6, 12, 60, 120, and 600 PPM imidacloprid. The results of these feeding studies yielded inconsistent results with as much as 50% survival at the 600 PPM level in some replicates. Based on these results, we suspect that the imidacloprid may be unevenly distributed in the leaf tissue over time, allowing areas of lower concentration for ACP to feed. We are now examining this hypothesis by measuring imidacloprid in different parts of the leaf (center vs leaf margin) to determine movement over time and potentially how long full leaf protection may last.