Failed Attempts to Establish IPM for Asian Cycad Scale and Coconut Rhinoceros Beetle on Guam

Abstract

Failed Attempts to Establish IPM for Asian Cycad Scale and Coconut Rhinoceros Beetle on
Guam

Aubrey Moore

Guam's ecosystems are under attack by invasive species. Many people know about extinction of
Guam's birds by the brown tree snake which invaded the island shortly after WWII. But the
contemporary ecological disaster which is currently happening in Guam's forests is not well known.
In 2002 a US Forest Service survey found the endemic cycad, Cycas micronesica, to be the most
abundant tree in Guam's forests and coconut palm, Cocos nucifera, to be the second most abundant
tree. Both species are now under severe attack by invasive insect species.
About 90% of C. micronesica trees have been killed by Asian cycad scale, Aulacaspis yasumatsui, first
detected in 2003. The predatory beetle, Rhyzobius lophanthae, was introduced and it is protecting
mature plants but no seedlings are surviving.
Coconut rhinoceros beetle, Oryctes rhinoceros, was first detected in 2007 and an uncontrolled outbreak
of this pest is currently killing coconut palms throughout the island. Following a failed eradication
attempt, Oryctes rhinoceros nudivirus (OrNV) and Metarhizium majus fungus were introduced as
biocontrol agents. OrNV unexpectedly failed as a biocontrol agent for CRB on Guam. Previously, this
pathogen produced excellent results when released on Pacific Islands infested with CRB. Subsequent
laboratory bioassays and genetic analysis showed that the CRB which invaded Guam belong to an
OrNV resistant biotype named CRB-G which is involved in all recent invasions of CRB in the Pacific.
The fungus, M. majus rapidly established and spread to CRB breeding sites throughout the island, with
infection rates measured between 10% and 38%. But this level of suppression was not enough to
prevent the current outbreak which was triggered by abundant breeding sites left in the wake of
Typhoon Dolphin which passed over Guam in May 2015.
Attempts to overcome these IPM failures will be discussed.