Judas Beetles: Discovering Cryptic Breeding Sites by Radio-Tracking Coconut Rhinoceros Beetles, Oryctes rhinoceros (Coleoptera: Scarabaeidae).

Abstract

The coconut rhinoceros beetle, Oryctes rhinoceros L., is a serious pest of coconut and other palms throughout Southeast Asia and on several Pacific Islands. Adults damage and sometimes kill palms when they bore into the crown to feed. In contrast, larvae feed only on dead plant material at breeding sites. Typically, coconut rhinoceros beetle populations are controlled with a combination of biocontrol, pheromone traps, and breeding site removal. A field trial was performed at two locations on Guam to test the feasibility of using the Judas technique, releasing radio-tagged adults to discover cryptic breeding sites, for potential coconut rhinoceros beetle control. Of 33 radio-tagged beetles that were released, 19 were successfully tracked to landing sites, 11 of which were considered to be active or potential breeding sites, in five different microhabitats. The remaining 14 beetles were lost when they flew beyond the range of receivers. Only one of the radio-tagged beetles was caught in the numerous pheromone traps present at the release sites. Percent emergence weight (%EW, ratio of current/emergence weight) varied significantly by the microhabitat to which coconut rhinoceros beetles were tracked. When microhabitats were further grouped, the difference in mean %EW between the arboreal (74 ± 2%) and the soil-associated (82 ± 3%) groups were found to be highly significant. The %EW for coconut rhinoceros beetles that were successfully located (78 ± 2%) and those that were lost (72 ± 2%) also differed significantly. Radio-tracking coconut rhinoceros beetles shows promise as a method to identify cryptic breeding sites, which could then be treated, removed, or destroyed.