Bark beetle found on Saipan 70 years ago resurfaces on Guam

John I Borja | Pacific Daily News

Show Caption Hide Caption Bark beetle on Guam Videos provided by University of Guam entomologist Aubrey Moore show bark beetles roaming about a piece of a nanåsu plant, also known as a beach naupaka.

A possibly endemic species that was last recorded 70 years ago is now a suspect in an investigation into what is causing one of Guam’s native plants to die.

The University of Guam worked with experts from the University of Florida to identify a specific type of bark beetle that’s attacking the island’s nanåsu, or beach naupaka, plant, according to UOG entomologist Aubrey Moore.

Landscape specialists noticed recently the plants were dying in several areas on Tumon Bay. Moore and his team examined samples of the affected plants and found small bark beetles inside. Beetle specimens were sent to the University of Florida, where they were identified as a specific type of bark beetle called Hemicryphalus argutus.

There are thousands of bark beetle species but this specific type was discovered on Saipan in the 1940s, Moore said. Up until now, that was the last time the beetle species was recorded, Moore said.

The nanåsu is an important part of Guam’s ecology, Moore said. It’s a hearty plant that’s salt-tolerant and grows on the beach. It can even grow on rocks and limestone, he said. More importantly, the nanåsu helps shape Guam’s beaches and prevents erosion.

“It’s not just ornamental. If we lose these plants, we lose our beaches,” Moore said.

The entomologist said it’s good news that the bark beetle isn’t invasive. The species evolved in this region, meaning the plant and beetle can co-exist, Moore said.

“I have no fear that this beetle can wipe out the plant,” he said.

While not much information is known of this specific beetle, others related to it feed on fungus, and the fungus is what kills the plant, he said. It’s possible that the bark beetles appeared only after the plant died and ate the fungus that killed it. He also noted that bark beetles carry fungus, and they could have brought the fungus into the plant.

Moore said an investigation into what is killing the native plant is ongoing.

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Coconut rhinoceros beetle

Meanwhile, research on a more harmful beetle is underway.

Moore is looking into ways to lure and kill the infamous coconut rhinoceros beetles that are plaguing the island’s coconut trees. UOG is collaborating with off-island experts to find solutions to control the beetle population.

Live beetles were sent to Maryland this week to see if a better lure can be created, Moore said. He also dissected beetles and sent guts to New Zealand where scientists can determine if they can create a virus to kill the beetle.

UOG will have a grant available later this year that will help it monitor the health and mortality of coconut trees. Moore said there currently isn’t a tree-monitoring program in place, and it's something that can help gauge how effective lures or viruses are against the invasive species.

The coconut rhinoceros beetle on Guam is so unique that it has its own biotype: CRB-G. It's been found in Palau, Hawaii and Papua New Guinea. Most of the newly reported infestations involve Guam’s beetle.

It’s very unlikely the species can be eradicated on Guam, but Moore hopes the virus can prevent the beetle from spreading further.

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Reporter John I. Borja covers infrastructure, environment and more. Follow him on Twitter @JIBreporter. Follow Pacific Daily News on Facebook.com/GuamPDN and Instagram @guampdn.