The project ‘Use of Stable Isotope Ratio Analysis (SIRA) for the identification of invasive species native in alien environments’ aimed to develop SIRA as an arthropod tree-pest decision tool to inform phytosanitary response.

Modern analytical technologies, used in other fields can be applied to entomological research and pest control. Wood-boring larvae assimilate the isotope ratios of the wood they feed on, and isotope signatures can provide clues to the geographic origin of the emerged adults. The Asian longhorn beetle (ALB) Anoplophora glabripennis is among the most damaging invasive tree-pest insects in Europe and North America, and its detection can trigger an eradication response. Knowing if the source of detected specimens is local or foreign can influence the degree of response. A captured beetle with a local isotope signature probably developed from an egg laid locally one or two years earlier. The response to this would involve much effort and destruction of trees to locate further adults, larvae and exit holes made by adults in order to eradicate the pest. A captured beetle with a foreign (e.g. Chinese) isotope signature is more likely to be the only beetle present and an opportunity exists to trace the imported host wood to determine whether other adults may have emerged. In this case, only lower-cost localised monitoring for additional adult beetles would be required.

A method based on the measurement of stable isotopes in adult ALBs to identify the origin of the wood from which they emerged was developed in the framework of the project activities.

The method can detect that an ALB has emerged from European wood in at least 95% of cases. The method was calibrated with ALBs from 11 locations in China (n=55) and 6 locations in Europe (Italy, n=28).

Additionally, samples of Monochamus galloprovincialis, Monochamus sutor, and Monochamus sartor – potential vectors of the pine wood nematode – from nine European countries (49 locations) were analysed.

To examine whether SIRA of one pest can instruct about another pest with a similar feeding habit, six pest species (n = 5 adults each) and timber from which they emerged 20 to 1047 days after seizure at US ports (between 2012 and 2016) were analysed for hydrogen and carbon isotope ratios. We found a positive offset for carbon from timber to beetle on all but one species on Populus wood.

Rearing beetles with lifecycles of 2 or more years in the laboratory is challenging. A most up to date guideline has been disseminated by USDA. However, to achieve higher survival rates from larvae to adult and create larger data sets, a more natural but controlled setting is recommended. While we demonstrated that SIRA can have a promising use in directing control efforts, more data may improve its power as an arthropod tree-pest decision tool.