Coconut Rhinoceros Beetle
by James A. Bethke
This column focuses on insects that pose a threat to the ornamental plant production industry and have good potential for invasion and establishment in California.
In April, my staff and I attended the Entomological Society of America annual meeting in Honolulu, Hawaii and during our visit it was interesting to note all of the panel traps (fig. 1) in the trees all around the island.
More than 2100 panel traps are being used to determine the distribution of the coconut rhinoceros beetle (CRB), Oryctes rhinoceros (L.), on Oahu. This beetle is a huge specimen (fig. 2) and the larval stage (fig. 3) principally feeds on coconut and oil palms, but recorded host plants include the date palm and a variety of palms grown as ornamentals such as Roystonea regia, Livistona chinensis, Corypha umbraculifera, Raphia ruffia and Wodyetia bifurcata.
Fig. 2. Adult coconut rhinoceros beetle, Oryctes rhinoceros (L.). Photo: Mark Schmaedick, Entomologist, Land Grant Program, American Samoa Community College.
It has also been recorded on pineapple, sugarcane, pandanus and banana. Larvae can be found developing in mulch piles and green waste much like the scarab beetles in southern California such as the green fruit beetle (fig beetle).
Fig. 3. Coconut rhinoceros beetle, Oryctes rhinoceros (L.) larva. Photo: Mark Schmaedick, Entomologist, Land Grant Program, American Samoa Community College.
As most of you are probably aware, we have been invaded by several giant palm weevils (red palm weevil and South American palm weevil), but weevils (snout beetles) are very different than the CRB, which is a scarab beetle. Common scarab beetles include June beetle species; dung beetles, rain beetles and chafers, and immatures commonly feed on dung and detritus (decaying matter). Feeding damage on growing palms resembles the damage caused by the giant palm weevils. CRB damage palms by boring into the center of the crown where they damage and feed on the terminal growing point and on the sap. They damage developing leaves, which eventually expresses as v-shaped cuts in the expanding fronds and holes through the midrib.
CRB is a major pest of palms in India, the Philippines, the Palaus, Fiji, Wallis, Nukunono, American Samoa, Samoa (formerly Western Samoa) and Guam. CRB is native to the Asian tropics, but was accidentally introduced to western and central Pacific islands. Interestingly, CRB was likely introduced throughout the Pacific primarily as a result of the increased sea traffic during World War II (Nishida and Evenhuis 2000). CRB was first detected in Hawaii in December 2013 in Pearl Harbor on coconut trees. Hawaii has begun an intensive eradication effort against CRB. Oahu residents are being asked to check their mulch piles and green waste for any potential breeding populations.
Here in Southern California, we have been faced with the threat of the South American palm weevil, Rhynchophorus palmarum, reaching across the Mexican border into San Diego County. This beetle is one of the many giant palm weevils that threaten our palm tree industry in southern California. CRB is another looming threat that you should be aware of because as we all know, what ends up in Hawaii usually ends up in California.
James A. Bethke is County Director and Farm Advisor for Nurseries and Floriculture, UC Cooperative Extension, San Diego and Riverside Counties.
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