Coconut rhinoceros beetle (CRB, Oryctes rhinoceros) has imposed severe economic and ecological damage to plantation and urban palms on the Pacific Islands onto which it has invaded. The beetle historically achieved its invasive range due in part to military activities in the region, and initially established on Oahu nearby Joint Base Pearl Harbor-Hickam. The prevalence of CRB-infested palms near military lands raises the risk that equipment and personnel transfers will result in continued accidental introductions to locations where palm species are a prominent feature of local ecosystems (e.g., California). To reduce the risk of further damage to ecosystems and economies, there is a marked need to develop and deploy sensitive surveillance tools that allow detection of initial CRB incursions, the location and spatial extent of nascent CRB populations, and the success of control programs. In addition, identification of individuals with the virus-resistant biotype is a high priority as it influences policy and management decisions. In this project, the project team will adapt an existing environmental DNA (eDNA) survey protocol for use in (1) surveillance of CRB at the points of likely initial incursion, (2) detecting nascent satellite populations outside of these incursion sites, (3) accurately delimiting a nascent population’s geographical range and (4) estimating local CRB abundance and the proportion of individuals that are the virus-resistant biotype. If the project team can achieve these goals, it will transform Department of Defense (and other agencies’) approaches for to CRB surveillance and control.
eDNA is material, such as shed cells, waste products, exuviae, and reproductive secretions, that is continuously released into the environment by all living organisms. This DNA material can be collected within bulk samples of water, soil or sediment, and then assigned to species using standard molecular techniques. The project team has developed and field-tested sampling tools that allow aggregation of terrestrial pest insect eDNA for other pest insects. The project team will execute a series of lab-based experiments designed to vet a previously identified CRB mitochondrial marker for use within an eDNA survey. eDNA samples will be assessed in the laboratory to differentiate between the biotypes that are susceptible or resistant to biocontrol pathogen, Oryctes rhinoceros nudivirus. Finally, the project team will conduct a series of field experiments as a precursor to validate the CRB eDNA survey on Hawaii and other locations of interest.
Development of a rapid and cost-effective eDNA survey can substantially elevate the chances that a very small number of CRB individuals can be detected when present, and can provide critical information on local CRB abundance in support of active control measures. This includes (1) increasing detection rates of initial incursions around high-traffic sites (airports, seaports) and of satellite populations, (2) producing more spatially accurate delimiting surveys, (3) identifying the presence and relative abundance of virus-resistant CRB biotype individuals, and (4) confirming the success of site control or eradication efforts.