Coconut Rhinoceros Beetle threatens palms in the Pacific Region

Coconut is an important crop in Pacific societies. They serve as a source of oil, fiber, food and timber. It is also an important small-holder crop that contributes to food security, improved nutrition, employment and income generation. Production of coconut is affected by the introduction of an invasive pest, the scarab beetle Oryctes rhinoceros, commonly known as coconut rhinoceros beetle. The coconut rhinoceros beetle is a major pest of palms especially of coconut and oil palms, and its presence in an area can have damaging effects and pose a threat to the industry. The beetle is endemic to the tropical Asia region and the beetle’s feeding characteristics are damaging and can be fatal for palms.

CRB’s history of introduction into the Pacific goes back to the year 1909 when infested rubber tree plants were brought into Samoa from Sri Lanka (formerly known as Ceylon). The beetle established itself and spread across Samoa. Not long after its introduction in Samoa, reports of its presence in other Pacific Island countries were made including Palau and Papua New Guinea. This spread was believed to be through the uncontrolled movement people and goods in th region. In 1963, a viral pathogen, Oryctes rhinoceros Nudivirus (OrNV) was discovered in Malaysia and hailed as the biological controlling agent to end the phase of the damage coconut rhinoceros beetle was causing to palms. OrNV established in the Pacific eventually suppressing the CRB population to a level insignificant for any devastating impacts.

However, in 2007, an unexpected incursion was discovered in Guam, called CRB-G (G for Guam). This Oryctes rhinoceros behaved differently to the other Oryctes rhinoceros in the Pacific. Eradication was attempted but the CRB-G population could not be controlled, even despite the introduction of the existing OrNV biological control. The failed attempts lead to population boom across the island of Guam. Eventually the CRB-G population spread and observations of similar damaging symptoms were reported in other Pacific Island countries like Port Moresby, Papua New Guinea (2009), Oahu, Hawaii (2013) and Honiara in Solomon Islands (2015). Coconut rhinoceros beetle was back.

This photo, Coconut Rhinoceros beetle is copyright (c) 4th October, 2016, SPC. Available under https://www.spc.int/updates/news/2016/10/curbing-the-coconut-rhinoceros-beetle-in-the-pacific

The observation of the presence and destructive characteristics of the beetle raised concerns and a group of researchers from Ag-Research (New Zealand), The University of Guam and the Secretariat of the Pacific Community (SPC) collaborated on research aiming to control the invasive population in Guam and identifying the new haplotype together with its distribution in an attempt to control the beetle with OrNV. The research involved various processes including the trapping of beetles in 12 different geographical locations in the Asia-Pacific region were coconut rhinoceros beetle is known to be present including Guam. Pheromone lures were used to collect live adult beetles for the research. Once beetles were caught, the researchers extracted the mid-gut, extracted DNA and used the DNA to identify the beetle species and also to map out where the different variants of coconut rhinoceros beetle are found.

The work of Marshall, Moore, Vaqalo, Noble and Jackson resulted in identifying the haplotype involved in the coconut damages in Guam and in some other Pacific Island countries. Results of the research confirmed that the origin of the initial CRB population in Samoa and the Pacific from Sri Lanka. It also found that the CRB-G haplotype is genetically distinct from the CRB populations already established in the Pacific region and is highly damaging to palms. It also found that CRB-G is tolerant to the OrNV isolates commonly used as the biological control of coconut rhinoceros beetle.

With these findings, it can now be confirmed that CRB-G poses a threat to the Pacific Island countries as the beetle is capable of damaging and killing palm trees, including coconut, otherwise sometimes described by locals as the “Tree of Life”. More so, the findings of the researchers have aided in identifying the cause of the issue thus, allowing for improvement and effective control of coconut rhinoceros beetle, through biosecurity measures such as effective border monitoring and restrictions from countries containing CRB-G and also by looking at new isolates of OrNV for effective control. These efforts will contribute to the life expectancy of the still swaying palms trees in the Pacific Islands.

Bala Asigau is a postgraduate student in the Postgraduate Diploma in Applied Science. She wrote this article as part of her assessment for ECOL 608 Research Methods in Ecology.

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