State hopes new rules for plant transport, compost stop invasive pest’s costly spread

HONOLULU (HawaiiNewsNow) - Coconut rhinoceros beetles and their much-larger larvae have infested Oahu, according to state agriculture officials.

But they’re hoping that new interim rules will help keep them from spreading to the rest of the islands, especially in materials that are meant to help in the wildfire recovery effort on Maui.

The rules restrict palm plants taller than 4 feet from Oahu.

But they also restrict compost, mulch and other landscaping products heading to the neighbor islands.

The invasive beetles that damage coconut trees have been spreading on Oahu since they were discovered on the island nearly 10 years ago. Last month, the first CRB was found on Maui — a dead one, inside a compost bag shipped from Oahu.

“Where the beetles entered more than likely is on Oahu. Where they exited could have been on Oahu, could have been on Maui. At this point, we don’t know that. We don’t have any evidence to say that that’s the case,” said Jonathan Ho, interim manager of the state Plant Quarantine Branch.

Ho said the adult beetles can be spotted by the damage they do to palm fronds. The eggs and larvae are a lot harder to detect.

“So you have these large volumes of mulch. Obviously, there’s no good way to inspect. And then you have movement of commercial products — potting mix, things like that — which can be infested,” Ho said.

“It likes mulch. I breeds in mulch. It lays their eggs there, it’s where their larvae live,” said Adam Lee, CEO and co-owner of North Shore Stables, which has been using ways to eliminate the beetle larvae without using pesticides.

Green waste and plant materials are also being used for erosion control for the Maui wildfires, including in so-called “socks” that block debris from going into storm drains.

“You see them when you do construction, when you see them along drains and stuff like that,” Ho said, adding that a lot of them are needed in Maui’s wildfire areas, especially Lahaina. “You’re trying to prevent all of that stuff going into the water, and now you have miles and miles of area that you need to contain.”

North Shore Stables has been training pigs to find and eat CRB larvae in mulch as an alternative to using insecticides. They say they still have a goal of eliminating the beetle on Oahu.

“They know that we can’t surrender Oahu because that’s basically saying the other islands will inevitably have infestations,” said Lee. “And that’s not OK.”