DNA barcode efficacy for the identification of economically important scale insects (Hemiptera: Coccoidea) in South Africa

Scale insects (Sternorrhyncha: Coccoidea) are one of the most invasive groups of insects. They are sedentary, cryptic, and often resemble the plant parts that they feed on. This coupled with increased international trade in fresh agricultural produce, makes them a major quarantine risk. An important limitation in controlling these pests involves species identification. When scale insects are intercepted on imported produce, they must be rapidly and accurately identified, using morphology-based keys. This is time-consuming and requires extensive taxonomic experience. In addition, intercepted specimens are often immature or damaged, making identification difficult or impossible. A reliable complementary tool is needed for identification. DNA barcoding may be of great value for this purpose. In this study we investigate the suitability of the nuclear regions 18S and 28S as complementary DNA barcodes to the mitochondrial CO1 gene, across 10 scale insect families. Combining multiple criteria, our results indicate that the concatenation of CO1 and 28S greatly improves the identification success rate of scale insects to 91.5 %, demonstrating the utility of DNA barcoding in pest management.