Fears of Invasive Beetle Spreading to West Hawai‘i

Queensland Longhorn Beetle. PC: BIISC

An invasive beetle caught the attention of Big Island farmers in the Spring of 2018 because of its assault on fruit trees in East Hawai‘i. Now, some farmers believe the pest may have spread to the west side of the island.

Acalolepta aesthetica, also known as the Queensland longhorn beetle, is destroying cacao, citrus, breadfruit and kukui on farms across the county’s windward side. It is believed the beetle may also pose a threat to other fruit trees and native forests.

Ken Love, executive director of Hawai‘i Tropical Fruit Growers, said a farmer in South Kona recently showed him what he believes to be evidence of the longhorn beetle inundating citrus and avocado trees.

“He was alarmed by the quantity of these things on the bark,” Love said.

Franny Brewer, communications director for the Big Island Invasive Species Committee, said she would be hesitant to say that the beetle has been confirmed in Kona. Several people have reached out to BIISC to report the presence of the pest on their properties, only for investigation to prove it was a different type of beetle or insect.

“I would be hesitant to say it turned up in Kona because there’s nothing between (the areas where it’s been confirmed) and there” Brewer said.

According to BIISC, there is no known treatment for the pest. However, farmers dealing with infestations on their properties are invited to attend an informational session on battling the beetle.

The session will run from 5 p.m. to 6:30 p.m. on Feb. 3 at Hawai‘i County’s Aupini Conference Room in Hilo. Love said speakers from the state Department of Agriculture, the county and BIISC are expected to be on hand.

“I hope they’re more proactive about (dealing with the beetle) than they’ve been in the past,” said Love, referencing what he’s considered to be a slow response to problems like the coffee berry-borer, which has seriously threatened the Kona coffee crop in recent years.

As for the Queensland longhorn beetle, BIISC wrote on its website that the pest was likely introduced to Hawaiian shores by accident via imported commodities from the Queensland region of Australia.

Beetles like the longhorn in question are wood-borers and are known to burrow into wooden packing materials. Acalolepta aesthetica, the pest’s scientific name, is related to the Asian longhorn beetle, which is infamous for devastating forests in North America with estimated costs for control at more than $600 million since the 1990s, according to the BIISC website.

The pest lays its eggs in the wood of weak or dying trees. When the larvae hatch, they tunnel through the branches, weakening the trees further and disrupting natural processes necessary for the trees to survive. In one case in Puna, an infested Sago palm became so weak it collapsed under its own weight, BIISC said on its website.

BIISC estimates the beetle arrived around a decade ago and slowly began to proliferate. By 2017,  specimens were collected in Hawaiian Acres, Kea’au and Kurtistown, BIISC said. In summer of 2018, specimens were captured in Pāhoa and Hilo, indicating the beetle may be becoming even more pervasive. In 2019, Love identified the pests’ presence in South Kona.

There is no known treatment for an infestation of the longhorn beetle. Adult beetles appear to be attracted to light at night, where they can be collected, BIISC said. Regular use of insecticide may also prevent infestations, but the Department of Agriculture has said research is sparse.

The best policy, according to BIISC, is prevention. The organization has advised caution when moving possible host plants, reiterating that infested trees should be destroyed.

BIISC is still accepting live samples of the Queensland longhorn beetle as of January, 2020. Specimens can be dropped off at 23 E. Kawili St. in Hilo. Photos can also be submitted by referencing the BIISC website.