As the coconut rhinoceros beetle invasion threatens Guam’s coconut trees, it has inspired regional collaboration by researchers determined to understand what attracts a rhino. Decoding chemical cues that attract rhino beetles may unlock the secret to saving the island’s palm trees.
Dr. Matthew Siderhurst, a chemical ecologist from Eastern Mennonite University, and technician Dominick Skabeikis of USDA-ARS-Pacific Basin Agricultural Research Center, were recently on island working with the Coconut Rhinoceros Eradication team and University of Guam entomologist Dr. Aubrey Moore.
“One outcome of our collaboration with Dr. Siderhurst is the important improvement of adding lights to our CRB bucket traps, which has resulted in a three-fold increase in the number of beetles found in these traps,” said Moore. Many CRB reports indicate beetles being attracted at night to lit areas. “On this trip Mat and Dom are is collecting chemical compounds from local coconut trees and compost material for analysis at his lab in Hilo.”
Siderhurst held a postdoctoral research associate position with Dr. Eric Jang at the USDA-ARS-PBARC in Hilo, Hawaii, working to identify attractants for several economically important invasive insects. Hawaii is very concerned about the possibility of rhino beetles showing up in their coconut trees, so they are funding Jang and Sidehurst’s studies on CRB. The concern in Hawaii was heightened last week when a live rhino beetle was caught in the baggage area at the Honolulu International Airport. It is not known if the beetle was a hitchhiker from Guam.
Sidehurst has been conducting electrophysiology tests to find out which chemicals excite the beetle.
“We attach electrodes to their antennae and our equipment records the beetles’ reaction to the plant volatiles we pass over them,” said Siderhurst. “Our hope is to isolate the chemical in coconut trees that attracts the adult beetles to feed or aggregate, and use it as a improved lure to attract them to traps in order to suppress the population.”
The experiment to isolate chemicals from coconut trees involves wrapping the crown of a coconut tree in a huge plastic bag and then inserting glass tubes into the bag in order to pump air through the tree and extract the plant volatiles. The volatiles are then put through a gas analyzer to identify individual compounds.
University of Guam extension agent and Coconut Rhinoceros Eradication team leader Roland Quitugua is curious as to why the CRB is attracted to coconut palms and not areca (betel nut) palms. “I find coconut palms with rhino damage growing right next to betel nut trees that haven’t been disturbed by the beetles at all. What is it that draws them to feed on the coconut trees and not touch the betel palms?”
The Japanese proverb, “None of us is as smart as all of us,” certainly applies to the difficulties of controlling invasive species introduced to island ecosystems that have developed in isolation. USDA-ARS-PBARC Hawaii, USDA-APHIS, the U.S. Forest Service, the Guam government, and the University of Guam have funded this collaborative study of coconut rhinoceros beetles in the hope that we can learn how to control them before much more damage is done.
To report CRB sightings in Guam, call 475-PEST(7378). (UOG)