Detection of an invasive biotype of Oryctes rhinoceros (L.) in the Pacific

Introduction: Oryctes rhinoceros (coconut rhinoceros beetle; CRB) is a major pest of coconut and oil palm, but the discovery of O. rhinocerosnudivirus (OrNV) in the 1960s enabled the successful management of populations in Pacific Island Countries. Augmentative release of OrNV continues to be an important mechanism for CRB management. For ~40 years after adoption of this biocontrol strategy, no new outbreaks of CRB were reported from uninfested palm growing islands in the Pacific, ensuring continuity of palm based village economies. However, the situation has recently changed. For first time in ~40 years, CRB invasion into completely new areas has been reported in the Pacific (Guam, Port Moresby, Honolulu, and Honiara).

Methods: Palm damage assessments and CRB collections were conducted across several geographic locations within the Pacific and SE Asia regions. Pathogen challenge bioassays were performed on outbreak CRB using isolates of OrNV. Molecular analyses were carried out on tissue samples obtained from CRB collections to characterize differences between CRB populations and to detect presence of OrNV.

Results/Conclusion: Common to all new outbreak areas is the high incidence of severe palm damage not seen since the introduction of OrNV. Attempts to introduce OrNV into the Guam CRB population were unexpectedly unsuccessful, raising the possibility that the CRB population that invaded Guam (the CRB-G ‘biotype') could be resistant to the commonly applied OrNV isolates. Molecular analyses of several CRB populations demonstrated that the CRB-G ‘biotype' is also found in Honolulu, Port Moresby, Honiara, and Palau.