coconut rhinoceros beetle

A male coconut rhinoceros beetle specimen. (Photo: Wikimedia Commons)

As if Hawaii didn't have enough invasive species to deal with, a giant tree-killing beetle from Southeast Asia may now be poised to wage war on the islands' iconic palms.

The coconut rhinoceros beetle was found near Honolulu in late December, stirring fears it might repeat its costly invasions of India, the Philippines, Fiji, Samoa, Guam and several other Pacific islands. The beefy beetles bore into the crowns of coconut palm trees, where they injure young tissue and drink the sap. They cut through growing leaves as they bore deeper into the crown, creating signature V-shaped cuts in the palm fronds.

This damage can kill the trees directly, and also leaves them vulnerable to secondary infections. After feeding, the adult beetles — which only live for about three months — ditch the trees and go breed in piles of trash, compost or other organic materials.

Hawaii's first coconut rhino beetles were discovered Dec. 23 on a golf course at the U.S. military's Joint Base Pearl Harbor-Hickam. No one is sure how they got there, but at least one major breeding site and several smaller ones have been found so far, spurring an aggressive campaign to stop the invasion before it spreads. Authorities have already set up about 500 pheromone-baited traps in the area, and they're asking the public to keep an eye out for the pests and to remove any rubbish piles that might attract them.

The Hawaii Department of Agriculture (HDOA), the U.S. Department of Agriculture (USDA) and the University of Hawaii (UH) are collaborating on the effort, hoping to avoid what has recently unfolded in Guam. That U.S. territory could lose up to 70 percent of its coconut palm trees to rhino beetles, which one Guam mayor has described as "worse than the brown tree snake," the most notorious invasive species in Guam's modern history.

"The threat of the coconut rhinoceros beetle has been a growing concern in Hawaii since it turned up in Guam in 2007," says Dr. Neil Reimer, administrator for HDOA's Plant Industry Division. "We have initiated the strong, coordinated efforts among HDOA, USDA, UH and other partners that will be required to effectively manage this invasive pest."

coconut rhino beetle damage

Holes bored into the trunk of a palm tree by coconut rhino beetles. (Photo: Hawaii Dept. of Agriculture)

Hawaii can learn from Guam's experience, but it also has a few advantages. Since brown tree snakes wiped out most of Guam's native birds last century, it has few predators left to eat the beetles. Hawaii has also lost lots of birds to alien predators like mongooses, but its avian populations are likely still strong enough to keep the beetles in check — with a little help from exotic opportunists like rats, pigs and mongooses. Oahu also has nearly three times the land area of Guam, and smaller islands are more susceptible to invaders.

Still, Oahu authorities are taking nothing for granted. Coconut palms may no longer be a cash crop in Hawaii, but they're huge for local ecology, culture and cuisine, not to mention their iconic role as ornamental plants and tropical touchstones for tourists. Dying palm trees are now a safety risk on Guam's beaches, according to the Pacific Daily News, and Hawaiian officials worry rhino beetles might also eat more economically vital crops.

Coconut rhino beetles are reportedly unfazed by most of Hawaii's legal pesticides, but CNN reports the state is mulling more drastic measures — including biological controls like fungi and viruses — if the invasion gets out of hand. In the meantime, researchers from the University of Guam are helping Hawaii fight the beetles with newly designed traps that work better than older models. Solar-powered, ultraviolet traps with light-emitting diodes catch three times as many beetles as traditional pheromone traps, for example, while "barrel traps" that mimic the insects' breeding sites can be 10 times more effective.

If you see signs of coconut rhinoceros beetles on Oahu, or on any other Hawaiian island, call the HDOA's pest hotline at 808-643-PEST (7378). And to learn more about the state's efforts to beat the beetles, check out this report from Honolulu's KHON-TV:

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Giant 'coconut rhino beetle' invades Hawaii
The beetle has already wreaked havoc around the Pacific, and recent sightings in Hawaii could spell trouble for its iconic palm trees.