Rhinoceros Beetle Huge Threat
By Glenn I. Teves, County Extension Agent, UH CTAHR
It moved around undetected for almost two years before it was found through a routine survey by University of Hawaii and USDA Plant Protection and Quarantine (USDA-PPQ) officials. The Coconut Rhinoceros Beetle (CRB) is one of the largest beetles to invade Hawaii and was discovered in an area surrounding Joint Base Pearl Harbor-Hickam. By that time, it was found in a one mile radius around the base. Red flags were raised in 2007 when it was first found in Guam, an island half the size of Molokai where a major U.S. military base covers half the island. It was only a matter of time before it would catch a direct flight to Hawaii. A dreaded and destructive insect of coconut, the CRB is found in many areas of the Pacific, south Asia, India, Africa, and the Middle East.
The beetle life stages include egg, larvae, pupae, and adult. Eggs are whitish brown, 1/8 to 3/16 inches, first oblong but growing into a rubbery circle in four to five days. Eggs will hatch in about 12 days and go through three larval stages or instars, maturing into large C-shaped larvae of 2 3/8 to 4 1/8 inches long. The pupae stage will live in soil or organic matter near trees for about 20 days, and will form into a cocoon. Adults will stay in cocoons for another 11 to 20 days to allow their exoskeleton to harden. Females can lay 70 to 140 eggs and will deposit them in logs or in heaps of organic matter. Adult beetles can range in size from 1 3/16 to 2 ¼ inches. A distinctive horn curving backward is found on both male and female beetles, but the male horns are larger. Under ideal conditions, three generations can be produced in a year. Decaying coconut wood is a preferred breeding area for this beetle.
The most damage is done during the adult stage by boring into the crowns of healthy coconut palms and penetrating from 3 to almost 20 inches into the cluster of leaves at the top of the tree. They bite through the unopened leaves and will most often injure the main rib of fronds. It will then bore outward again, emerging from the base of a central frond in the crown. The adult beetle will feed on sap produced by the injury. Mature fronds often have patches of missing foliage like they’ve been cut with a scissors to make V-shaped patterns in the fronds, and also holes in the midribs.
Beetles will also feed on breadfruit, mango, kamani, and hala, but coconuts are its preferred host. It has a large host range and, in the absence of the plants list above, will feed on sugar cane, ironwood, taro, banana, pineapple, agave, and many species of ornamental palms, possibly the native Loulu palm. Natural enemies include rats, pigs, and mongoose, and may also be attacked by certain ant species and other beetles. There’s also a fungus and a virus known to be fatal to this beetle.
If you find this insect or suspect damage by this insect, please contact the Molokai Maui Invasive Species Committee at 553-5236. Thanks to Hawaii Landscape Magazine as the source of information for this article. For more information, please visit: