Classical insect and mite taxonomy is a highly specialised skill. Taxonomists generally operate within a few areas of expertise and have limited opportunities to pass on their knowledge to the next generation or colleagues in other countries. DNA sequencing is increasingly used to complement classical taxonomic methods for the rapid and accurate identification of arthropod species and is of particular use to researchers and diagnosticians involved in plant protection. However, this method relies heavily on the accuracy and availability of sequences on public databases which although useful for biodiversity studies can be less reliable at the species level. Ideally, all barcode sequences should have been derived from a vouchered specimen, which was initially identified by a taxonomic expert, however this is not always the case. Errors can also be compounded if any newly generated molecular identification is based upon a previous misidentification.

Some important plant pest groups, such as scale insects (Infraorder: Coccomorpha), can be difficult to distinguish between morphologically. Furthermore, barcoding scale insects using the standard cytochrome c oxidase subunit I (COI) barcoding gene region has proven to be problematic, with alternative gene regions needing to be considered (Park et al, 2011). This Euphresco project aimed to exchange knowledge and expertise between partners on molecular barcoding methods for challenging arthropod pests. In-house studies on extraction and sequencing techniques were shared, some of which have been summarised in this report, including: DNA extraction method comparisons; comparing storage media for insects prior to extraction; and comparing alternative gene primer sets for identifying Coccomorpha specimens. A Test Performance Study (TPS) for the comparison of molecular methods identifying specimens of the Infraorder Coccomorpha (soft scales and mealybugs) was performed. One DNA extraction method using a non-destructive technique was evaluated, and the effectiveness of three barcoding primer sets were assessed in their ability to identify the Coccomorpha specimens tested. The participants found the TPS useful for optimising methods for extracting and sequencing this insect group.