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‘Ōhi‘a: Tree of Life


Summer 2019

Majestic ‘ōhi‘a line Pihea Trail above Kalalau Valley. Photo credit: Nate Yuen.

I ola ‘oe

I ola mākou nei

My life is dependent on yours.

Your life is dependent on mine.

No other Hawaiian tree embodies this ‘olelo (saying) like ‘ōhi‘a. These trees are unique to Hawai‘i—found here and nowhere else in the world—covering nearly one million acres across the state. ‘Ōhi‘a are pioneers of fresh lava flows, breaking down rock and creating conditions for other plants and animals to thrive. As the backbone of Hawai‘i’s native forests, ‘ōhi‘a are a critical source of freshwater, shelter, and food. Too, their myriad root system prevents soil erosion and helps keep our reefs and marine life healthy. The many relationships nurtured by these trees have inspired hula (dance), mo‘olelo (stories), mele (songs), and ‘oli (chants).

A Newly Identified Disease


A disease called Rapid ‘Ōhi‘a Death (ROD) has killed hundreds of thousands of ‘ōhi‘a on Hawai‘i Island. The disease is caused by two newly discovered species of fungi: Ceratocystis lukuohia, destroyer of ‘ōhi‘a, and Ceratocystis huliohia, disrupter of ‘ōhi‘a. Both fungal pathogens can infect ‘ōhi‘a when the fungal spores enter through an open wound in the tree. Over the course of a few months, the fungus spreads inside the tree until it cuts off the flow of water, killing the tree. There is no known cure or way to eradicate the disease, so we must work together to protect ‘ōhi‘a by preventing the spread of ROD wherever possible.

In May 2018, C. huliohia was first detected on Kaua‘i’s east side. In November, it was also detected in additional areas on the south and north sides of the island. Then, in December 2018, both C. huliohia and, disturbingly, the more aggressive C. lukuohia were detected in the forest behind Anahola Mountain. At this time, all of these detections are in remote areas--from elevations of 500 to 1,500 feet above sea level--and not on maintained trails.
 


Do you hike?

Do you like to enjoy Kauai’s forests--hiking, hunting, birding, hiking? You can help to mālama (take care) of our ʻōhiʻa trees and prevent the spread of Rapid ʻŌhiʻa Death disease by picking up your own FREE ROD decontamination kit! Complete with a boot scrubbing brush, a spray bottle of 70% rubbing alcohol, and directions, this is something you'll want to keep in your vehicle, so it's readily available. Don’t forget, to help save ‘ōhi‘a,  please clean your shoes and gear before and after entering the forests. And when you’re out there, tread carefully to avoid stepping on ʻōhiʻa roots. Any break in the bark can allow the ROD-causing fungus to enter the tree. Remember, when you save ‘ōhi‘a, you save more than just a tree. To pick up your kit, drop us a note at saveohia@hawaii.edu. While supplies last.


Installation of Boot Brush Stations Begins


Recently, the Hawai‘i State Department of Land and Natural Rosources' Division of Forestry and Wildlife (DOFAW) started installing boot brush stations at trailheads around the island. The use of these will help prevent the spread of the microscopic fungal spores that can be carried in mud. Please help save ‘ōhi‘a by giving ROD the brush off!

Watch this 90-second video to learn about proper bio-sanitation protocols.

Help stop the spread of Rapid 'Ōhi'a Death by cleaning your boots and gear.

Science Spotlight

Scientists recently confirmed that Ambrosia beetles are a definite culprit in the spread of the fungal pathogens that result in ROD. Here's how:

  1. As decomposers, beetles are attracted to dead and dying trees. When they enter a dead ʻōhiʻa, they burrow beyond the bark into the sapwood.
  2. If a tree has died of ROD, these beetles will ingest Ceratocystis lukuohia and/or Ceratocystis huliohia in the exact spot where the fungus colonizes, or grows--the sapwood, or xylem.
  3. Live fungal pathogens are then released into the environment by way of the sawdust-like frass that beetles excrete.

In their research study, scientists with the University of Hawai
i’s Department of Plant and Environmental Sciences proved the hypothesis that the sawdust-like frass excreted by beetles can contain viable Ceratocystis pathogens.

In general, the microscopic fungal pathogen enters ʻōhiʻa through wounds in the tree. Any wound that penetrates the bark makes ʻōhiʻa susceptible to the disease. There are many ways a tree can be wounded--by animals, humans, machinery, and strong winds.

Simply put, wounds allow the fungal pathogens to enter the tree, and beetles release the pathogens back into the environment.

This research is important, because it helps with forest management decisions. For example, if laboratory testing indicates an ʻōhiʻa has died of ROD and there is evidence of beetle activity releasing frass into the environment, foresters many decide to fell a tree and cover it with a tarp to reduce the chance of beetle activity. If there is no evidence of beetle activity and there’s a possibility that felling the infected ʻōhiʻa will injure a nearby healthy ʻōhiʻa, foresters may decide to leave the tree standing.


Upcoming Events

July 23: Growing ʻŌhiʻa and Collecting ʻŌhiʻa Seeds for Conservation Workshop.

August 3rd: Anaina Hou Garden Party.

August 15 - 18: Kauai County Farm Bureau Fair.


Please check the KISC website for details and the most up-to-date listings of events.


Field Trips: Seed Collecting

Lyon Arboretum is leading a mission to collect two billion ʻōhiʻa seeds from as many different ʻōhiʻa trees across the state as possible, and you can help. These seeds will be kept in seed banks in several locations and secured for possible future restoration efforts. If you'd like to participate in upcoming group outings to collect seeds, email Kim at saveohia@hawaii.edu. Please indicate whether or not you've attended any of Lyon Arboretum-sponsored ʻōhiʻa seed banking workshops. Click here to learn more about this project.

FAQ

Each issue, we’ll answer a frequently asked questions. Want to submit a question? Email saveohia@hawaii.edu.

Q: How can I tell if a tree has ROD? 

A: ROD-causing fungi cannot be seen from the outside of the tree; it grows and spreads within a tree for months or longer before the leaves start to wilt and brown. Suddenly, it will seem, leaves on entire  limbs or even the entire crown of the ‘ōhi‘a will turn yellow and, then, brown. Dead leaves don’t immediately drop and may remain on branches for some time. To confirm whether an ‘ōhi‘a has ROD, a sample of the wood must be taken by a trained technician and tested in a lab.

 

Saving 'Ōhi'a: Hawai'i's Sacred Tree

For the past few months, we’ve been screening the documentary, “Saving ‘Ōhi‘a: Hawai‘i’s Sacred Tree.” Now, it’s available to view online in its entirety here. This 30-minute film is set on Hawai‘i Island but covers many of the same issues Kaua‘i faces. It’s a great way to quickly understand the role the tree holds in our environment and in the Hawaiian culture, as well as, the science behind the disease and ways we can help stop its spread. Just recently, the documentary film was awarded three Emmy Awards, the television industry's equivalent of the Academy Awards.

 

You Can Help Save 'Ōhi'a

1) Keep your eyes open. If you see ʻōhiʻa with a limb or crown turning brown, take a picture and contact Kaua‘i Invasive Species Committee 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, weed-whacking, and stepping on roots 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 soapy water and dry on high heat.

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 the vehicle's 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.

Sharing is Caring. Please share this newsletter with your friends and colleagues--anyone who is in a position to help educate neighbors and visitors about ʻōhiʻa and Rapid ʻŌhiʻa Death. Thank you! 

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Copyright © 2019 Saving 'Ōhi'a, All rights reserved.


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