POTENTIAL BIOLOGICAL CONTROL OF THE COCONUT RHINOCEROS BEETLE ON O‘AHU, HAWAI‘I

Abstract

Many islands throughout the Pacific have had their palm trees devastated by Oryctes rhinoceros (Coleoptera: Scarabaeidae: Dynastinae), the coconut rhinoceros beetle. O. rhinoceros primarily feeds on coconut palms, Cocos nucifera, but can feed on a variety of other palms and plants of economic value. Integrated pest management is often used to control O. rhinoceros, with a combination of mechanical, cultural, chemical, and biological control methods. O. rhinoceros’s spread across the Pacific was influenced by agriculture, shipping, war, and tropical storms. In 2013 it was detected on the Hawaiian Island of O‘ahu. Due to the regulations associated with bringing in biological control agents to the Hawaiian Islands, a survey was conducted to identify local entomopathogenic fungus strains to test on the O. rhinoceros larvae. Soil samples from around O‘ahu were collected and 73 strains of Beauveria spp. and Metarhizium spp. were tested on lab reared O. rhinoceros first instar larvae. Heterorhabditis indica and Steinernema feltiae entomopathogenic nematodes were collected on O‘ahu for trials as well. O. rhinoceros larvae were reared in the University of Hawai‘i Arthropod Containment Laboratory, with field caught adults brought into the colony weekly. These larvae reflected the field population on O‘ahu, and were used in laboratory assays involving entomopathogenic nematodes and fungi. The entomopathogenic nematode testing did not yield substantial mortality, while the entomopathogenic fungal strains yielded greater than 60% mortality with five prominent strains. Promising entomopathogenic fungi results led to field testing on field caught larvae as well.