Dead `ohi`a in Kauai forest. Credit: DLNR photo. |
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The most aggressive form of Rapid `Ohi`a Death fungus has been
identified in a stand of native forest on the island's east side, just months after the less aggressive type was
found on the island.
The latest form is a fast-killing disease to which few or no
`ohi`a are resistant.
`Ohi`a is perhaps the most significant tree of the Hawaiian
forest—the canopy tree in many areas, and a nesting site for many birds. Its
attractive red flowers are a major food source for Hawaiian forest birds, and
its leaves and flowers are significant in Hawaiian culture.
Photos, a press release and other information are available
at the website of the state Department of Land and Natural Resources, which
announced the finding.
Here is the press release:
(Lihue)-Detection of Ceratocystis lukuohia, the more
virulent of the two fungal pathogens causing Rapid ʻŌhi‘a Death (ROD), has now
been confirmed in three trees on Department of Hawaiian Home lands parcel
behind Kalalea Mountain on the east side of Kaua‘i. This first detection of C.
lukuohia comes after the other pathogen resulting in ROD, Ceratocystis
huliohia, was detected on Kauai in three distinct locations this past year.
“These three trees that tested positive for C. lukuohia were
spotted by our rapid response team as they were conducting botanical surveys
across the island,” said Sheri S. Mann, Kaua‘i District Manager for the DLNR
Division of Forestry and Wildlife (DOFAW). “Later, a team trekked by foot to
visually inspect and take samples from the tree.”
ʻŌhi‘a 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 obviously news we didn’t want to hear,” Mann said.
“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.”
A benefit for Kaua‘i is the hard-earned research conducted
on Hawaii Island where ROD was identified more than four years ago. Hundreds of
thousands of trees have died due to ROD on Hawai‘i Island, more than 90 percent
due to C. lukuohia. Earlier this year, scientists at ARS described the
two-different species of fungi that cause ROD as C. huliohia and C. lukuohia.
Both species 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 ʻōhiʻa tree, C. lukuohia can kill a tree
within weeks,” said James B. Friday, the extension forester with the University
of Hawaii.
The Kaua‘i ROD Working Group does not know exactly when or
how the disease arrived on Kaua‘i-whether it was the result of human activity
or on its own, e.g. 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 ʻōhiʻa. It has a critical role in
the ecosystem’s function,” said Tiffani Keanini, project manager of Kaua‘i
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 ʻōhi‘a, 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 ʻōhiʻa on Kaua’i 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.
As there is no known cure to ROD, prevention is the key to
ensuring it doesn’t spread and both Kama‘aina and visitors can help by
following these key five guidelines:
1) Keep your eyes open. If you see ʻōhiʻa with a limb or
crown turning brown, take a picture, and contact KISC via email
(saveohia@hawaii.edu) or phone (808-821-1490). Samples of the wood must be
taken by trained technicians and tested in a laboratory to confirm the presence
of the ROD fungi.
2) Avoid injuring ʻōhiʻa. Wounds serve as entry points for
the fungus and increase the odds that the tree will become infected and die
from ROD. Avoid pruning and contact with heavy equipment wherever possible.
3) Clean gear and tools, including shoes and clothes, before
and after entering the forest and areas where ʻōhiʻa may be present. Brush all
soil off tools and gear, then spray with 70% rubbing alcohol. Wash clothes with
hot water and soap.
4) Wash your vehicle with a high-pressure hose or washer if
you’ve been off-roading or have picked up mud from driving. Clean all soil off
tires–including mountain bikes and motorcycles–and vehicle undercarriage.
5) Don’t move ʻōhiʻa wood or ʻōhiʻa parts, including
adjacent soil. The disease can be spread to new areas by moving plants, plant
parts, and wood from infected areas to non-infected areas.
©Jan TenBruggencate 2018