Schematic of our expectation that larval emerald ash borers (Agrilus planipennis; EAB) deposit sufficient DNA as they develop under the bark to be detectable in tree cores from within or nearby feeding galleries. EAB DNA deposited in feeding galleries may also become incorporated into the tree’s transport tissues surrounding the galleries and, if so, cores collected at some presently unknown distance from a gallery may correspondingly contain detectable EAB DNA. No matter the source, we expect the availability of EAB DNA from tree cores to be highly seasonal and peak either when larvae are most actively feeding or when the host tree moves large quantities of nutrients and water to the leaves or roots – shown here by downward arrows – in the transport tissues (beginning and end of the growing season, respectively) or a combination of the two. In the present study, core samples were extracted from sample trees at breast height (1.37 m) above ground level.