Rapid ‘ohi‘a death spreading quickly

  • Contributed by Daisy Chung

    A graphic shows the rapid ‘ohi‘a death process.

  • Contributed by state Department of Land and Natural Resources Division of Forestry and Wildlife

    Brenna Fowler with the Kaua‘i Invasive Species Committee, left, and Christa Mcleod with the Hanalei National Wildlife Refuge stand next to the boot-brush station installed at the Okolehao Trail at Hanalei National Wildlife Refuge.

  • Contributed by Kaua‘i Invasive Species Committee

    This map illustrates how widespread both species of critters causing rapid ‘ohi‘a death have become on Kaua‘i.

  • Courtesy J.B. Friday / University of Hawai‘i

    An ‘ohi‘a lehua flower is seen in the rain.

  • Contributed by state Department of Land and Natural Resources Division of Forestry and Wildlife

    An ‘ohi‘a tree in Koke‘e State Park that tested positive for Ceratocystis lukuohia is cut down by the state Department of Land and Natural Resources Division of Forestry and Wildlife crew to help stop the spread of the fungal disease.

  • Contributed by state Department of Land and Natural Resources Division of Forestry and Wildlife

    ‘Ohiʻa trees in Kokeʻe State Park that tested positive for Ceratocystis lukuohia are wrapped in a tarp to help stop the spread of the fungal disease.

KOKE‘E — Since the first detection of a more-harmful fungal pathogen known to cause rapid ‘ohi’a death was discovered in December of 2020 in Koke‘e, the state Department of Land and Natural Resource Division of Forestry and Wildlife and Kaua‘i Invasive Species Committee have cut down three infected trees.

KISC’s ROD Outreach Specialist Kim Rogers said their combined six field experts found a total of six trees with the Certocystis lukuohia fungal pathogen which is known to spread naturally, through the air and through the movement of mud, along Miloli‘i Ridge Road within Na Pali Kona Forest Reserve in Koke‘e.

“The other trees, we wrapped them in a tarp to prevent beetles from getting in and the fungus from escaping into the environment,” Rogers said. “So that leaves three trees that we didn’t want to fall because of the repercussions that dropping the trees would cause.”

According to Rogers, ambrosia beetles are attracted to dying trees, and they like to burrow themselves and create their own food source within the ‘ohi’a trees. However, they are only a part of the problem when it comes to spreading the disease.

“And they go in and they do their thing,” Rogers said. “Unfortunately, where this fungus grows is inside, just behind the bark of the tree in what’s known as the sapwood. And that just happens to also be where the beetles burrow into and create galleries, and that’s where they get their food and nourishment. And so the beetles burrow in there, and they kick out what’s known as frass, and that frass is their excrement, but it can also contain live fungal spores.

“So when they kick that frass out, that’s what’s dropping to the ground in the mud. And that’s what we move around,” Rogers said.

So far, KISC’s and DOFAW’s field crew have created a quarantine-like fence built around the three infected trees to avoid further movement of the fungal spores through the mud by the shoes of any nearby hiker.

Rogers said there are things that the public can do when they visit any part of Koke‘e to help stop the spread of the fungal spores which can’t be seen with the naked eye (see the informational box).

“One of them is via sanitation,” Rogers said. “Leave the mud where you found it, which of course is easier said than done. This fungus itself is microscopic. So it’s not like you can look at the bottom of your boots and be like, ‘Oh look, there’s a seed, I need to get rid of it.’ The first step is to use a boot brush or scraper to get as much mud off your boots and vehicle tires as possible.

“And then the second step is going to use rubbing alcohol — spray that on your footwear or your backpack or your truck tires, and that will kill the fungus,” Rogers said.

Rogers said this same fungal pathogen has been studied heavily on Hawai‘i Island for six to eight years now.

“Most of the science that we are basing all of our work off of comes from Hawai‘i Island, where they’ve lost over a million trees to this disease,” Rogers said.

The ‘ohi‘a trees throughout the islands are a vital part of the environment, and are the keystone species for numerous endemic and endangered plants and animals, said Rogers.

“‘Ohi‘a is super-critical to our watershed,” Rogers said. “So the water we drink — the water we use to irrigate our fields. We rely on ‘ohi‘a for that process that helps draw moisture from the air and helps hold moisture in place. A healthy ‘ohi‘a forest has a canopy understory and ground cover that helps hold rain, and it’s a place that helps prevent erosion.”

The two fungal species, Ceratocystis huliohia and Ceratocystis lukuohia, were first detected on the northern side of Kaua‘i in May of 2018, and since then Rogers said their field crew, the Hawai‘i Rapid ‘Ohi‘a Death Rapid Response Team, has been using technology to detect infected trees, like the most-recent detection of the lukuohia fungal pathogen in Koke‘e back in December.

“One of the things we’ll do as soon as that tree was detected in Koke‘e, we went out and did a benchmark, drone survey,” Rogers said.

“An aerial survey that gives us a picture in time. We’re going back at least monthly and doing that. And the reason why that’s important is that the only way we can detect a tree with symptoms of ROD is visible light. What happens is the leaves will turn this reddish-brown color. Sometimes if you catch it at its height, it’s like a super-bright red color.”

Rogers said volunteers are welcome to get in touch with KISC to be a part of their future “adopt-a-boot” brush-station program, where volunteers would coordinate a time to clean the sanitization boot-brush stations around the island.

Here’s how to help prevent ROD spread

From the University of Hawai‘i at Manoa’s College of Tropical Agriculture and Human Resources come the following tips to help prevent the spread of rapid ‘ohi‘a death:

• Avoid injuring ‘ohi‘a;

• Don’t move ‘ohi‘a wood or ‘ohi‘a parts;

• Don’t transport ‘ohi‘a inter-island;

• Clean gear and tools, including shoes and clothes, before and after entering forests.

• Wash the tires and undercarriage of vehicles to remove all soil or mud before and after entering forests.

•••

Stephanie Shinno, education, business, and community reporter, can be reached at 245-0424 or sshinno@thegardenisland.com.

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