In 2009, a resident of Orchidland subdivision in Puna on Hawaiʻi Island found a strange beetle with extremely long antennae on the screen door. This report marked the first detection of a new species of longhorned beetle, Acalolepta aesthetica, in Hawaiʻi and the United States. Lacking an official common name, the beetle is called the Queensland longhorn beetle, reflecting its native home in Australia.
Despite survey efforts by the Hawaiʻi Department of Agriculture, the beetle wasn’t detected again for years, but that first incursion wasn’t a one-off and its population continued to grow. Four years later it was seen again. Sightings increased as the beetles spread across Puna. Over the last 3 months, the Big Island Invasive Species Committee has received over a dozen reports.
The arrival of this new insect has officials with the Hawaiʻi Department of Agriculture (HDOA) concerned. According to HDOA entomologist Darcy Oishi, the Queensland longhorned beetle could significantly damage citrus and other trees. The larvae tunnel through living wood creating big galleries, similar to termites, but on a much bigger scale. Oishi says, “They make these giant weeping wounds in branches or the trunk of a tree. The damage can cause dieback in a limb or the death of a tree.”
“They make these giant weeping wounds in branches or the trunk of a tree. The damage can cause dieback in a limb or the death of a tree,” says Oishi.
Not much known about this beetle, perhaps because it’s not a pest elsewhere. Its arrival in Hawaiʻi marks the first time this beetle has acted invasively with potential impacts only now being realized. The list of trees damaged by beetle larvae continues to grow. It’s been found tunneling through lemons, limes and other citrus; Polynesian-introduced trees such as ulu (breadfruit) and kukui; favorite food crops like cacao (chocolate) and possibly avocado; and introduced species such as gunpowder trees and sago palm. As the current world expert on the beetle, the Hawaiʻi Department of Agriculture has not identified any natural enemies in Hawaiʻi nor any effective controls methods.
Complicating research on control options is the presence of native longhorned beetles in our state. Important both as wood decomposers and food for native birds, our Cerambycid beetles are one of the many native insects that show amazing rates of adaptive radiation. From what entomologist estimate was three distinct arrivals, over 120 species evolved. One of the largest native insects in Hawaiʻi is a Cerambycid beetle; measuring 2 inches from tip to tail with sweeping antennae as long as its body, Megopis reflexa is closest in appearance to the invasive Acalolepta aesthetica.
The new wood-boring pest is not yet known from Maui or any of the other Hawaiian Islands, but farmers and residents can take steps to prevent its arrival. The best way to keep it from moving interisland is to not bring green woody material between islands, particularly if the vegetation shows signs of damage, such as weeping wounds where a beetle may have laid its eggs and larvae entered the tree.
Be alert to sightings of the beetle, often attracted to house lights at night. The adult measures from 2-4.5cm (3/4-1 ¾ inches) in length. The antennae on the male are twice as long as the body – giving rise the moniker “longhorned.” Antennae on the female are shorter. On either side of the thorax (the body part behind the head) are two thorn-like spines. The abdomen is dimpled and looks as though covered in peach fuzz. In contrast, the native Megopis beetle has ridges running down the abdomen, giving it a striped appearance.
Oishi also suggests looking for wounding on trees. The beetle larvae can be even larger than the adults and as they leave the tree to mature, they leave behind large holes, up to 1.25 cm (1/2 inch) in diameter, as big around as a pinky. Other indications are sawdust-like frass being pushed out of holes on the trunk, girdling on trunk, sap oozing from where the adult laid eggs, and branch dieback and drop. Find more details and the official pest advisory on the HDOA website: http://hdoa.hawaii.gov/pi/ppc/new-pest-advisories/.
On Maui, report any suspected sightings. Collect the beetle and contain it in a secure container. Take clear digital photos of the beetle and record the location, type of plant or tree, date, and how you found it. If you see damage on a tree, take photos. Use an object (coin or ruler) for reference. Email the photos and the information to HDOA.PPC@HAWAII.GOV or report it online through 643PEST.org.
Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia’i Moku, “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy, and quality of life.
This article was originally published on August 10th, 2018 as part of the Kiaʻi Moku Column for the Maui News.
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