As a result of international trade, many bark- and wood-infesting insects are inadvertently transported in wood packing materials (WPM) such as crating, dunnage, and pallets. WPM is suspected as the likely pathway for most of these borers, although the exact mode of entry into the USA is unknown for all 25 borers. The top 10 countries of origin were, in decreasing order, Italy, Germany, China, Spain, Belgium, Russia, India, Mexico, France, and United Kingdom. We initiated studies in 2004 and 2005 to evaluate post-treatment insect colonization of logs and lumber with varying amounts of bark. Acer rubrum (red maple), Carya glabra (pignut hickory), Pinus resinosa (red pine), and Quercus rubra (northern red oak) were selected. All bark was retained on the logs. The logs were either heat treated according to ISPM-15 standards (56°C core temperature for 30 minutes) or left as untreated control logs. Overall, bark- and wood-boring insects (primarily Cerambycidae and Scolytidae) colonized and successfully reproduced in all treated and untreated logs of all four tree species tested. Although our studies indicated that borers will infest barked surfaces of WPM after heat treatment under ideal field conditions, it was not known to what degree treated WPM contains bark, and how often borers live are associated with the bark. A survey revealed that about 0.11% of all marked WPM entering the USA harbored live borers. The results of the surveys and studies may help regulators to judge the relative risk of bark associated with WPM and whether there is justification to require that WPM be manufactured from bark-free wood.

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