Amy Tsuneyoshi
Hawai‘i Herald Columnist
Have you been digging around in your compost pile and uncovered huge, fat, white wriggling grubs that crawl on their sides and curl up into a “C” shape? If you are on O‘ahu, it may be coconut rhinoceros beetle larvae. There are other beetles that have similar larvae or grubs, but those don’t grow to be as large as the CRB larvae, which can become three inches long!
Coconut Rhinoceros Beetle (oryctes rhinoceros) is native to Southeast Asia and was first detected on O‘ahu in 2013 in the Pearl City peninsula region. It primarily feeds on young coconut leaves but has been reported to impact other palms, cycads and fibrous plants like banana, papaya, sugar cane, pineapple and hala. If the beetle population is large, the feeding damage can ultimately kill the plant.
The adults are two inches long and have a hard black body. They have a horn on their head like their namesake – rhinoceros, and can fly, but not great distances. Since they are nocturnal, you probably won’t see them out during the day. They chew holes into unfurled leaves or soft wood to extract the plant liquid and create tunnels as they burrow. In their wake, they leave behind frass and chewed up plant fiber, which is perfect material to lay their eggs. The tiny eggs hatch in one to two weeks and the emerging larvae start feeding on decaying material, growing up to three inches in five months.
There are various ways CRB can spread, which they’re doing so on O‘ahu, and the most likely method is by being transported unknowingly in infested green waste, compost, mulch, and potting soil while they are in the egg or larvae stage. When purchasing commercial bags of compost/potting soil, check for large holes in the bag. It’s possible for the beetles to chew through the bag to lay their eggs. As of July 1, 2022, the Hawai‘i Department of Agriculture implemented an interim rule that prohibits transporting CRB host material without a permit. If you need a large load of mulch, make sure you are buying it from a compliant vendor that has gone through the training and are taking precautions to prevent the spread of CRB.
How can you help?
- Check your mulch, compost or green waste piles for any larvae or beetles.
- Monitor your palms and other plants for suspicious damage such as new palm leaves with “v” shaped damage, declining health of plants, or two-inch holes near the growing point of the plant.
- If you spot any damage or find beetles/larvae, please contact the coconut rhinoceros beetle response team at (808) 379-5244, info@crbhawaii.org, or report it online at crbhawaii.org.
Amy Tsuneyoshi grew up playing in the mud and still finds joy in getting her hands in the soil. She grows a variety of edible and ornamental plants in her urban jungle as well as Native Hawaiian plants. She has a degree in horticulture from the University of Hawai’i at Mänoa and is currently the President of the Friends of Hälawa Xeriscape Garden.
