An adult Coconut Rhinoceros beetle, Oryctes rhinoceros. (Image courtesy of the Coconut Rhinoceros Beetle Response Project).
You’ve probably heard the alarming news about grubs of the Coconut Rhinoceros beetle (Oryctes rhinoceros) reaching Hawaiʻi Island residences, likely transported within store-bought soil or compost products. These beetles, also known as Asiatic Rhinoceros beetles, can reach up to 2 inches in length, and are known for boring into crowns and unopened fronds of palms to feed on sap, eventually killing the “tree” (technically a perennial flowering plant). Wounds caused by the beetles may also suffer from secondary fungal or bacterial infections, further harming palms that survive the initial attack. The beetles are particularly harmful to young palms.
Grubs of the Coconut Rhinoceros beetle, Oryctes rhinoceros, which were recently found in Waikōloa on Hawaiʻi Island and possibly transported by store-bought soil or compost products (Image courtesy of the Hawaiʻi Department of Agriculture).
On Hawaiʻi Island, these invasive beetles pose a serious threat to our five endemic species of loulu palms: Pritchardia beccariana, P. gordonii, P. lanigera, P. schattaueri, and P. maideniana, with three of these species already designated as endangered or critically imperiled.
The beetles are dark brown to solid black with a distinctive, elongated horn on their head. They prefer to lay their eggs (which develop into grubs) inside soft, decaying palms, mulch, or compost. When disturbed, rhinoceros beetles can produce hissing squeaks, created by rigorous wing movements. Grubs are a cream color and reach 2 to 4” in length, and can look a lot like other (invasive) beetle grubs, so be sure to check out the links below for more identification resources, and report any sightings to state’s toll-free Pest Hotline: (808) 643-PEST (7378).
Signs of boring and damage on a local palm due to the Coconut Rhinoceros beetle (Image courtesy of the Hawaiʻi Department of Agriculture).
Where did the beetles come from:
Coconut Rhinoceros beetles are native to Africa, China, India, and Southeast Asia, and are an established invasive pest on several other Pacific Islands including Guam, Palau, Fiji, and Samoa. These fugly beetles have unfortunately been found on Oʻahu for about a decade now, and were first documented on Kauaʻi in May 2023. The case reported on October 11, 2023 in Waikōloa Village was the first confirmed report for Hawaiʻi Island, and the beetle grubs may have been inadvertently transported in bags of compost or mulch.
Partner agencies including the Hawaiʻi Department of Agriculture (HDOA), the Department of Land & Natural Resources (DLNR), and the Coconut Rhinoceros Beetle Response Team are working to to detect and combat the invasion. For more information on the beetle and the response to their invasion of the Hawaiian Islands, check out: https://www.crbhawaii.org/.
What can I do to help stop the spread of the Coconut Rhinoceros beetle?
Signs of invasion by a Coconut Rhinoceros beetle on a packaged compost bag (Image courtesy of the Hawaiʻi Department of Agriculture).
Please help prevent the spread of these beetles in your area. A few simple things you can do:
1) Report any sightings of grubs or beetles to the state’s toll-free Pest Hotline: (808) 643-PEST (7378). If possible, collect the grub or beetle in a jar and keep any soil, compost or plant packaging.
2) Try home composting and avoid purchasing soil or compost from off-island. See some excellent tips on home composting or join a composting workshop here: http://recyclehawaii.org/resources/at-home/backyard-composting/.
3) If you do purchase store-bought soil or compost, check for holes where the beetles may have entered (e.g., small bumps or needle-like punctures surrounding larger holes in the bag), and report any suspicious looking bags to store management and to the Pest Hotline: (808) 643-PEST (7378). DO NOT purchase bags with suspicious holes or punctures.
4) Before purchasing potted palm plants, check for signs of beetle boring. DO NOT purchase or bring home palms with suspicious holes or bore marks at the base of the fronds.
Additional information and identification resources
For more information on these pests, check out the Coconut Beetle Response Project (www.crbhawaii.org/) and the Big Island Invasive Species Response Committee (www.biisc.org/). Let’s all do our part to prevent a more serious invasion.
An endangered native loulu palm (Pritchardia kaalae) above the Makua Valley on Oʻahu (Image courtesy of Magnus Manske/ Wikipedia Commons).
