Wednesday

The Oryctes and Scapanes, pests of greatest concern

International recommendations from:

Marshall, S. D., & Moore, A. (2016). A New Coconut Rhinoceros Beetle Biotype Threatens Coconut and Oil Palms in Southeast Asia and the Pacific.

A coordinated regional collaboration should be organized and adequately staffed and funded to accomplish 3 objectives:
  1. Survey CRB populations throughout the Asian/Pacific region to delimit the geographical distribution of CRBGuam and identify its centre of origin. 
  2. Survey CRB-Guam populations from the centre of origin to find isolate(s) of OrNV (or other pathogens) that are highly pathogenic for the CRB-G biotype. 
  3. In vivo or in vitro propagation of selected OrNV isolates for auto-dissemination on islands infested with CRBGuam. It is estimated that these objectives will take four years to accomplish, with an annual cost of $1M U.S.
Scientific references

Marshall, S. D., Moore, A., Vaqalo, M., Noble, A., & Jackson, T. A. (2017). A new haplotype of the coconut rhinoceros beetle, Oryctes rhinoceros, has escaped biological control by Oryctes rhinoceros nudivirus and is invading Pacific Islands. Journal of Invertebrate Pathology149, 127-134.

The coconut rhinoceros beetle (CRB; Oryctes rhinoceros) is a major pest of coconut and oil palm, but the discovery and release of Oryctes rhinoceros nudivirus (OrNV) in the 1960s and 70s suppressed the pest such that no new invasions of uninfested islands by CRB were reported for over 30 years after implementation of the biocontrol programme. Surprisingly, a highly damaging outbreak was reported from Guam (2007), which could not be controlled by OrNV. Subsequently, new invasions have been reported from Port Moresby, Papua New Guinea (2009); O’ahu, Hawai’i (2013); and Honiara, Solomon Islands (2015). We have found that all of these outbreaks have been caused by a previously unrecognized haplotype, CRB-G, which appears to be tolerant to OrNV. PCR analysis shows that OrNV is generally present at high incidence in established populations of CRB, but is generally absent from the invasive CRB-G populations. CRB-G from Guam was not susceptible to OrNV infection by oral delivery, but injection of the virus did cause mortality. Further genetic analysis shows that CRB populations can be divided into a number of clades that coincide with the endemic and invasive history of the beetle. Analysis suggests that CRB-G originated in Asia, though the precise location remains to be discovered.



Reil, J. B., San Jose, M., & Rubinoff, D. (2016). Low Variation in Nuclear and Mitochondrial DNA Inhibits Resolution of Invasion Pathways across the Pacific for the Coconut Rhinoceros Beetle (Scarabeidae: Oryctes rhinoceros).

The coconut rhinoceros beetle (Oryctes rhinoceros) is a severe pest of coconut and other palms that has invaded the South Pacific in the last decade. The beetle can cause great economic losses, not only to agriculture but also due to indirect impacts on tropical aesthetics and tourism. In the last decade, new invasive populations of the beetle have been detected on Guam and Oahu, Hawaii. Despite the beetle’s extensive invasion history and economic impacts, little is known about its invasion dynamics. We used 1,480 base pairs of cytochrome oxidase subunit I mitochondrial and 814 base pairs of carbamoyl-phosphate synthetase, aspartate transcarbamoylase, dihydroorotase nuclear DNA to conduct a population genetics analysis on eight beetle populations from Thailand, Vietnam, Taiwan, and China in the beetle’s native range and Palau, American Samoa, Guam, and Hawaii in the beetle’s invasive range, in an attempt to resolve invasion pathways. Genetic diversity was insufficient to generate strong evidence for O. rhinoceros movement patterns. Mitochondrial DNA provided a clear but poorly supported population structure. Although nuclear DNA proved to be more diverse, population structure lacked clear signal. This lack of diversity is congruent with a rapid, recent invasion. There appears to be no genetic exchange between populations once they establish, implying that they are rare, human-mediated dispersal events.