LIHUE — Scientists have discovered the more aggressive form of Rapid Ohia Death in three trees behind Kalalea Mountain on Kauai and they’re moving fast to respond.
Lab results came back Monday on tests from the trees according to Kim Rogers, spokeswoman for Kauai ROD Working Group which is responding to reports — and those results showed Ceratocystis lukuohia, the more virulent of the two fungal pathogens causing Rapid Ohia Death (ROD) had infected the trees.
That makes four locations where ROD has been confirmed on the island since May. It is the first location where Ceratocystis lukuohia has been confirmed on the island.
This is obviously news we didn’t want to hear,” said Sheri Mann, Kauai District Manager for the DLNR Division of Forestry and Wildlife (DOFAW).“But within a day of learning the news, we scheduled a helicopter to conduct more digital mobile sketch mapping to identify any additional symptomatic trees. We followed that with pinpoint drone surveys conducted by the UH Hilo Department of Geography SDAV Lab and more tree sampling to try and determine the severity and distribution of the outbreak. It’s been a busy week.”
Ohia die for many reasons, although symptoms consistent with ROD include the sudden browning of leaves on limbs or the entire crowns of trees. The fungus is not visible on the leaves or the bark but grows in the sapwood just below the bark. The three trees that were sampled earlier this month stood out in a forest of green, because the entirety of the trees leaves had browned.
Samples were then sent to the USDA Agricultural Research Service (ARS) in Hilo for the necessary laboratory testing that confirmed C. lukuohia in all three trees.
“This is what’s been killed 90 to 95 percent of trees on the Big Island,” Rogers said. “It’s the most aggressive and that’s why response has been so fast.”
After the initial report, a team hiked into the Anahola area location by foot and investigated, then the drone team was called in to help.
Ohia on the Big Island have been dying from the disease for at least four years, and both species — C. huliohia and C. lukuohia — are new to science.
The difference between the two pathogens is how they move through the tree and how quickly they kill.
“The pathogen enters the tree through a wound; be it a broken limb, twig or, perhaps, a scuffed up exposed root. Whereas C. huliohia may take months to years to kill an ohia tree, C. lukuohia can kill a tree within weeks,” said James B. Friday, the extension forester with the University of Hawaii.
The Kauai ROD Working Group does not know exactly when or how the disease arrived on Kauai-whether it was the result of human activity or on its own, for example, via the wind.
Once additional lab results and drone imagery are available, the rapid response team will consult with the ROD science team to determine what management actions should be taken.
“Our priority is to save ohia. It has a critical role in the ecosystem’s function,” said Tiffani Keanini, project manager of Kauai Invasive Species Committee (KISC). “We are currently determining the best method to contain the spread and prevent ROD from entering pristine watershed areas. At this point, we are treating the recent outbreak with rapid response actions. As we learn more about the distribution and density of the affected area, we will likely adapt our management strategy efforts.”
The C. lukuohia detection site is located in a remote area at 550-foot elevation. This forest location is comprised of a mix of native trees and plants like ohia, koa, hala, and uluhe that are being crowded out by non-natives such as albizia, java plum, strawberry guava, and octopus trees. Unfortunately, any loss of a native tree will give rise to the faster-growing invasives unless aggressive native tree plantings take place.
“The Department of Hawaiian home lands supports the DLNR efforts to save the ohia on Kauai and we thank their team for their swift action to date. We will continue to monitor the situation and do all we can to assist. We encourage our beneficiaries and the public to follow the distributed guidelines to prevent more trees from becoming infected,” said Jobie Masagatani, Chairman of the Hawaiian Homes Commission.
The key to stopping the spread of ROD, according to scientists, is to watch for dying ohia trees and report them, avoid injuring ohia, clean gear and tools, wash vehicles well after being in the forest, and leaving ohia parts where they lie.
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Jessica Else, environment reporter, can be reached at 245-0452 or jelse@thegardenisland.com.
