Invasive beetle species in Hawaii can now be identified faster with new genetic test

Researchers at the University of Hawaii have developed a new genetic-testing method for identifying the invasive coconut rhinoceros beetle, which promises to be much faster than existing physical identification methods. The new tool, reported in the Journal of Economic Entomology, could be a significant step toward keeping the species—a damaging pest to coconut palm trees that was first seen in Hawaii in 2013—from becoming widespread.

Coconut rhinoceros beetle and a similar species, oriental flower beetle, are nearly indistinguishable until they've grown to their later life stages, which makes early detection difficult. Currently, egg or larvae samples from the field had to be raised in a lab until their third life stage, which could take several weeks, before insect scientists could determine which species they were looking at.

However, a genetic testing method known as a multiplex polymerase chain reaction (PCR) assay, can be used to identify the species with genetic material extracted from samples of the beetles' eggs, larvae, or excrement. Researchers Shizu Watanabe, Ph.D., and Michael J. Melzer, Ph.D., of the Department of Plant and Environmental Protection Sciences, College of Tropical Agriculture and Human Resources, at UH identified genetic markers in the beetles' DNA that can be used for differentiation via the test. Once samples are received in the lab, the PCR assay can be conducted in just a few hours, Melzer says.

The new method will help "ensure that eradication efforts are being directed at coconut rhinoceros beetle and not oriental flower beetle. This assay will help to prevent any misidentification in the field," Melzer says. "Such misidentifications might result in resources targeting oriental flower beetle, or worse, ignoring a coconut rhinoceros breeding site because the specimens discovered were identified as oriental flower beetle."

"For species that require highly technical expertise for identification, molecular assays represent a reasonably straight-forward approach for identification, either as stand-alone assays or in parallel with morphological identification," Watanabe and Melzer write in their article. "For pests of regulatory concern, rapid and accurate insect identification is essential, and molecular assays can address these needs."