Coconut Rhinoceros Beetle (CRB)

Adult male coconut rhinoceros beetle with a transparent background to demonstrate 2" length

~2 inches

Identifying

Adults

Adult coconut rhinoceros beetle (CRB) are black beetles averaging 2 inches in length with a visible horn. They are night-active and can fly. Although they do not bite, they may carry diseases, so they should not be handled with bare hands if possible.

Larvae

CRB larvae can grow up to three inches before pupating. These larvae crawl on their side and curl into a "C" shape when handled. As larvae, they live and feed on decomposing plant material. CRB prefer coconut palm green waste but can survive in most decaying plant material.

Lifecycle CRB- 11_30_20 (1).png

CRB breeding sites are typically established in decaying plant material like mulch, compost, decomposing stumps, or felled trees. After hatching from eggs, larvae begin feeding on the decomposing material. After growing through three larval stages, called instars, larvae pupate and emerge as an adult, leaving the breeding site. CRB spend roughly 3.5 months growing from an egg to an adult, and about 3 months as an adult. 

Where are they?

Historical Range

Although native to Southeast Asia, the distribution of CRB today includes many Pacific Islands, including O'ahu. To date, CRB has not been reported on any other Hawaiian islands, the mainland United States, Central America, or South America, but any tropical ecosystem that produces host species for the CRB is at risk of infestation.

How did it get to Hawai'i?

CRB was discovered at Mamala Bay, O'ahu December 2013. It is assumed the beetle came from Guam, as genetic testing has shown similarities between the beetles found in both places, although we do not know how it arrived. While it was first detected at the airport (HNL), there are both military and commercial flights from areas with CRB populations.

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Looking for damage

The CRB's preferred food sources are coconut, royal, date, and fan palm, but adult beetles can feed on other palm species and tropical plants like hala (pandanus), mai'a (banana), pineapple, kalo (taro), and kō (sugarcane). In areas with dense CRB populations, beetles are more likely to feed on something other than a palm.

Base of a palm frond with a two-inch bore hole cause by a coconut rhinoceros beetle

V-cut

If the beetle burrows into an emerging coconut palm frond, the damaged fronds will grow out of the crown in a v-shape with a scalloped edge. These distinct cuts form at a 45 degree angle. View the video below to see how v-shaped cuts are formed.

Close up of coconut palm with 2" bore holes caused by a coconut rhinoceros beetle

Bore hole

When feeding on coconut palms, CRB leave an oval-shaped hole about 2 inches across as it burrows through the innermost spear. This is called a bore hole and it can appear at the base of palm fronds or in leaves of other host plants. Similar damage can be caused by rats or other pests nibbling at the frond, but a bore hole is distinct in its clean oval shape.

Coconut rhinoceros beetle damaged shown on a fan palm. Coconut rhinoceros beetle feeding on immature palm fronds leave scalloped edges on the frond once it emerges.

Scalloped Edges

Whether the damage occurs on a fan palm or feather palm, scalloped edges will be present. As the beetle burrows into the crown of a palm, it cuts into un-emerged leaflets. View the video below to understand how scalloped edges are formed.

CRB Damage Video

How do traps work?

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  • We monitor ~3,100 traps island-wide.

  • Traps are checked anywhere from once a week to every 4 weeks.

  • The traps help us determine where we should be focusing our efforts by indicating potential populations. They are not effective in trapping every beetle.