Fight Against Rapid ‘ōhi’a Death Continues Statewide, 10 Years After First Discovered: Kauai Now

For more than a decade, land managers, scientists and pathologists have been struggling to find ways to protect trees from a fungal disease called Rapid ʻŌhiʻa Death, or ROD, that has killed more than a million lehua ʻōhiʻa, considered the most ecologically and culturally important native tree in Hawaii.

Last week, 10 years after the fungus was first discovered in the Puna District, many of the same people working on the front lines and behind the scenes gathered for a ROD Science Symposium.

JB Friday, a forester with the University of Hawai’i College of Tropical Agriculture and Human Resources, opened the symposium by outlining the history of ROD, beginning with the first suspected tree in 2012.

“The Puna landowner who reported the tree thought it was VOG (volcanic fog) or the effects of geothermal vents. When we saw the crowns (tops) of the trees dying, we thought it must be a root pathogen because there was no water getting to the tree. We then isolated different fungi, but we couldn’t find anything that would kill ʻōhiʻa trees,” Friday told the dozens of experts gathered for the symposium.

In 2014, another landowner from Puna brought some logs for testing and the UH Agriculture diagnostic lab isolated a world-known pathogen called Ceratocystis.

“That raised alarm bells,” Friday said. “Just because the fungus is in a tree doesn’t mean the pathogen is killing the tree.”

Dr. Lisa Keith of the USDA Agriculture Research Service conducted inoculation studies and found that the isolated pathogen was indeed able to kill ʻōhiʻa,” Friday explained.

The DLNR Division of Forestry and Wildlife and other organizations soon joined the hui to learn more about ROD and ultimately find ways to control this disease and keep Hawaii’s watersheds healthy.

Rob Hauff, DOFAW’s state conservation ranger, said, “We’re now finding ROD on Hawai’i Island, in pockets on Kaua’i and in a small number of trees on O’ahu. So far it hasn’t reached Maui.”

Since its initial discovery, scientists have identified two distinct forms of the disease, one more deadly than the other.

Friday credits the Hawai’i Department of Agriculture for instituting a quarantine on the movement of ʻōhiʻa plants and wood from Hawai’i Island to other locations in the state. “They listened to us. They said, this is bad. It was only on Hawai’i Island at that time and they put a quarantine in place.”

At first, researchers thought the bark beetles were spreading the fungus. One of the mysteries is how ROD reached O’ahu and Kaua’i and apparently skipped Maui.

“Our current model is that the disease is mostly spread through feces, the waste produced by beetles, but sometimes beetles can also transmit the disease directly as they forage for new trees,” Friday added.

Further research is needed to determine how often beetles directly spread the disease and to better understand the role of feral animals such as pigs, which have been shown to increase the likelihood of the disease occurring.
Research is still ongoing to better determine how ROD spreads.

On Friday, symposium attendees were encouraged to focus on protecting Hawaii’s critical ʻōhiʻa forests, which protect important watersheds in the state.

Hauff said some of the new scientific findings discussed at the symposium involve new tools, such as a beetle repellent known as verbenone.

“It’s a substance that you put on trees that keeps beetles away,” Hauff said. “So the hope is that where we detect the disease in new areas, it can prevent beetles from getting into trees and spreading the disease. It’s still experimental, but we hope it’s a tool that we can use in the future, particularly in places like Kauaʻi where the disease still has a chance to be contained.”

Scientists are also investigating the natural genetic resistance of some ʻōhiʻa populations to ROD.

“If we can propagate those trees and cross them with other resistant trees, we might have something that can help restore damaged forests,” Hauff said.

Although community attention to preventing the spread of ROD in forests has waned somewhat with other crises coming to the forefront, ROD remains an urgent problem. All those working to stop the spread of the disease are encouraged to know protocols such as not moving timber, treating tools and boots before entering forest areas, and reporting suspected infections to experts for immediate
attention.

“There are a lot of really smart people working diligently on this disease, and there is hope that we can eventually stop the spread of it,” Hauff concluded.