Across the USA and Canada, ash trees are being wiped out by a small green beetle, the emerald ash borer (Agrilus planipennis). …Rapid diagnosis of emerald ash borer infestation is important but beetle attack is not obvious in its initial stages. Trent University researchers devised a method to detect emerald ash borers by examining the metabolites present in the leaf. Sampling leaves is a rapid method of diagnosing a large number of trees, without the lengthy task of searching for larvae in the bark. …Following the chemometric results, 13 metabolites were shown to be appropriate biomarkers for the presence or absence of beetle attack. …The new method will speed up identification of this harmful pest since it only requires leaf samples, rather than a careful examination of the tree bark. Confirmatory detection of the beetle can then be carried out when positive results are obtained.