Identification by MALDI-TOF MS of Coleopteran insect pests collected in the field

In the context of museum and cultural heritage protection, rapid and accurate identification of Coleopteran pests is crucial. This study evaluated the effectiveness of MALDI-TOF MS in identifying seven species of Coleoptera collected between 2014 and 2023 from 17 French cultural sites. A total of 273 specimens (205 field-collected and 68 laboratory-reared) were analysed. Although reproducible and species-specific MS spectra were obtained, intra-species reproducibility was higher for laboratory reared specimens frozenly-stored compared to counterparts field collected and stored at room temperature. Two successive blind tests were done against the reference MS database including, firstly (ie, database 1, DB1), only laboratory-reared Coleoptera MS spectra, and secondly, those of DB1 upgraded with MS spectra from field collected specimens (ie, BD2). Correct identification at the species were obtained for MS spectra query against DB1 for species which possess homolog in the database. However, the spectra reaching threshold for relevant identification were coming from essentially laboratory-reared Coleoptera. An upgrading of the reference MS database (ie, BD2), improved identification performance for field specimens, although limitations remained for species with MS spectra of low peak diversity like Pentarthrum huttoni. In parallel, three specimens per species and storing mode were submitted to molecular identification using COI and 16S markers. For field samples, the rate of successful PCR product sequencing was lower than 10%, which was likely attributed to DNA degradation of these samples stored long term at room temperature. Overall, the study confirmed that MALDI-TOF MS appeared as a promising tool for Coleopteran pest identification, especially when reference spectra matched both species and preservation mode.