Rapid ʻŌhiʻa Death is a disease caused by two fungal pathogens. Ceratocystis lukuohia (destroyer of ʻōhiʻa) is the name of the more agressive fungus and Ceratocystis huliohia (disruptor of ʻōhiʻa) is the less agreessive fungus. Both of these fungal pathogens kill ʻōhiʻa, Hawaiʻi’s most abundant native tree.
The fungus enters the tree through a wound. A wound can be caused in many ways and might not be visible. Humans can wound trees by running over roots with a lawnmower, cutting through bark with a weedwhacker, pruning, cutting into trees to mark trails, hiking over exposed roots, etc. Strong winds, broken branches, included bark, and roots growing over lava rock can also cause wounds large enough to allow infection. Once the fungus enters the tree it grows into the vascular system (sapwood) and stops water from moving up to the crown of the tree.
The ROD-causing fungi are not visible on the outside of the tree, so a few characters may help determine if your tree might be infected. First, an apparently healthy tree's crown will turn from green to yellow then brown and appear dead over a few days to weeks if it has ROD. Next, leaf death will not be scattered but entire branches or the entire crown will die at once. If the tree is in a location were ROD is rare or unconfirmed, then it is possible that the tree died from something other than ROD such as injury or other pathogens. There are several diseases that kill ʻōhiʻa trees and show symptoms similar to ROD. If the tree is in a location where ROD is already prevalent, then it’s very likely that the tree has died from ROD infection. To be positive that the tree has ROD, a wood sample must be submitted for testing.
When the fungus infects a tree, it may take a year or longer before the tree shows symptoms of the disease (i.e., before the tree actually looks like it’s dying). Once a tree shows symptoms it usually dies within a few weeks. It seems that the disease does not kill trees as quickly in colder and drier locations.
Not at this point, but more detections have been made especially in the past two years. The more aggressive ROD-causing fungus, Ceratocystis lukuohia, has been confirmed on Hawaiʻi Island and Kauaʻi. The less aggressive fungus, C. huliohia, has been confirmed on Hawaiʻi Island, Kauaʻi, Maui, and Oʻahu.
The exact origins of the ROD-causing fungi are unknown, but we know that they are not native to Hawaiʻi. ROD is an exotic/introduced disease. There are several hypotheses for how these fungi originated: 1) a strain was brought in on a plant carrier that wasn’t showing symptoms of the disease, 2) a different strain was brought to Hawaiʻi and mutated or 3) two separate strains were brought to Hawaiʻi and recombined to create the strains that are killing ʻōhiʻa.
The fungal species that cause Rapid ʻŌhiʻa Death are specific to plants – humans will not be affected.
So far, the ROD-causing fungi are specific to ʻōhiʻa –you do not have to worry about ROD infecting other plants.
The fungi live in the sapwood of infected ʻōhiʻa trees and the spores can live for a year or more after the tree is cut. Moving wood such as firewood or posts from infected trees will move the fungal pathogens. In addition, humans can move fungi on clothing, shoes, gear (such as backpacks), and equipment (such as saws, machetes, and machinery). Beetles boring into infected trees create a fine boring dust mixed with infectious fungal spores that can settle to the ground and mix into the soil under ʻōhiʻa trees. If off-road vehicles drive through infected stands they can pick up mud from under the trees and transport the fungus to new locations.
No, not without a permit. The Hawaiʻi Department of Agriculture has declared a quarantine rule that prohibits interisland movement of all ʻōhiʻa plant or plant parts from Hawaiʻi Island including:
For more information on Hawaiʻi Department of Agriculture rules and recommendations see: http://hdoa.hawaii.gov/blog/main/reportingohiawilt
Several types of beetles, including ambrosia beetles and long-horned beetles, bore into infected trees and create a fine dust called frass. This beetle-made frass is contaminated by fungal spores and can be blown on the wind, spreading the disease. So far, studies have found that around 10% of beetles test positive for the ROD fungus, yet there is no evidence that beetles themselves cause ROD disease in healthy trees.
The fungus grows inside the sapwood of infected trees and not on the bark or leaves. The fungal spores themselves are not windborne. However, beetles boring into infected trees create a fine dust that is contaminated by fungal spores and can be blown on the wind, spreading the disease.
Scientists, researchers and land managers are working together to understand various aspects of this new disease.
Some of the current research includes:
There is currently no cure for trees that have already become infected with Rapid ʻŌhiʻa Death. Avoiding injuries to ʻōhiʻa is the best way to prevent disease from occurring. Keep lawnmowers, weed trimmers, and pruning saws away from ʻōhiʻa trees. Step over or around ʻōhiʻa roots while hiking.
Don't track disease-causing organisms around. Brush all soil and debris off of shoes, gear, and tools and then spray with 70% isopropyl (rubbing) alcohol. When spraying, coat shoe soles and allow the solution to sit for 15 seconds before hitting the trail.
There are currently no recommended fungicides (fungus-suppressing chemicals) for treating Rapid ʻŌhiʻa Death. Researchers are experimenting with different chemicals, however a successful chemical would only be used in a greenhouse setting or on individual trees. Using a fungicide would likely be expensive because the chemical would require repeat applications. A successful fungicide would also not be able to cure a tree that is already infected, but it may be able to slow the fungal growth and prolong the life of the tree.
Practice the “5 things you can do to help prevent the spread of ROD.”
If you’d like to do more, go to the homepage and click on the “How to Help” tab at the top.
If you think your ʻōhiʻa tree has ROD, there are several actions you can take. Read about our current recommendations. You can email photos of the tree, a description of the timeline of your observations (seeing a healthy tree progress to dead) and the location of the tree (e.g., neighborhood, town, etc.) to the UH extension forester, J. B. Friday (email@example.com) or the UH ROD educational specialist Corie Yanger (firstname.lastname@example.org). You can also reach them by phone.
Hawai'i Island residents can mail or deliver wood samples to Lisa Keith, Research Plant Pathologist, USDA/ARS DKI-PBARC, 64 Nowelo St., Hilo, HI 96720. Residents on other islands can submit samples to the local Hawai'i Department of Agriculuture Plant Quarantine Branch. A short video demonstrates how to take wood samples without felling the tree.
We recommend that you call an arborist who has been certified by the International Society of Arboriculture (ISA). Talk with the arborist about his/her current decontamination procedure as well as practices we recommend to prevent the spread of ROD. The Big Island Invasive Species Committee (BIISC) has a list of Certified Arborists for Hawaiʻi Island.
If you are fairly certain that the tree is infected and dead, then we recommend that you have the tree cut down safely. We recommend felling the tree on a still day to minimize blown sawdust and using a sharp saw to create chips rather than dust. You may use the wood as fuel for an imu, fireplace, smokehouse or barbecue on site but you may not dispose of it in an open brush fire unless you get a burn permit from the Department of Health. You can also cut the tree up and cover it with a tarp, cloth or weed mat to contain any dust or frass created by boring beetles. The fungus can live in the wood for at least four years.
Because the ROD fungus enters trees through wounds, the best thing you can do to protect your trees is prevent them from getting injured. Mechanisms of injury include: lawnmowing, weedwhacking, cutting, sawing, pruning, etc. If you have grass that grows up to the edge of your tree, pull the grass back or put down a mulch or solid barrier (such as plastic or rocks) around the base of the tree, about 6 inches away from the trunk, so that grass-trimming equipment will not accidentally injure the tree. Also, avoid stepping on ʻōhiʻa roots.
There are many ways to help spread awareness about ROD. Start to educate your family and friends about the threat of ROD and share and practice the 5 things everyone can do to prevent the spread of ROD. Invite a ROD researcher to give a talk in your community and help to organize the event. Request a ROD informational booth at a community event and volunteer at the booth (contact UH educational specialist, Corie Yanger for Hawaiʻi Island or the ROD Statewide Outreach Coordinator, Ambyr Mokiao-Lee for other islands). Print or request ROD brochures, stickers, handouts to share in your community.
Even if you don't have ʻōhiʻa on your property, you may come into contact with ʻōhiʻa. Think about whether you use forest products (for example, wood or lei materials), hike or hunt. If you participate in these activities, it is highly important to share and practice the 5 measures for preventing the spread of Rapid ʻŌhiʻa Death. ʻŌhiʻa are the foundation of our forested watersheds in Hawaiʻi and are responsible for replenishing our fresh water supply. Educate friends and family on the importance of this issue and help to prevent spreading ROD.
Yes, ʻōhiʻa can be burned safely in a fireplace, barbecue, imu, or smokehouse but take precautions to prevent spreading Rapid ʻŌhiʻa Death. Burn ʻōhiʻa firewood obtained from your property or from your neighborhood. ROD-causing fungus will not survive heat from a fire, will not get carried in the ashes, and will not be a threat to humans as the fungus is specific to plants.
If you have to move ʻōhiʻa wood, keep it contained in a box or another enclosed vessel. At the very least, cover the wood with a tarp to keep wood particles from flying around.
If wood is cut to firewood size before it's moved, there will be less chance of moving the disease than if they are moved and then cut. Buyers should be particularly aware of the risk of spreading ROD by cutting at a new location, especially areas of mostly healthy ʻōhiʻa forest. When cutting ʻōhiʻa, use as few saw cuts as possible to reduce the amount of fine particles. Once wood is bucked up, use an axe to cut wood into suitable firewood pieces.
Alternatives to ʻōhiʻa firewood include kiawe (Prosopis pallida) and macnut (Macadamia integrifolia). REMEMBER: always check firewood to for diseases and pests, like ROD or fire ants, before you move it.
Yes, ʻōhiʻa can be sold legally for firewood; however, please handle the wood and advertising responsibly to avoid spreading Rapid ʻŌhiʻa Death (ROD) disease.
Within the Island of Hawaiʻi there are no legal restrictions to moving or selling ʻōhiʻa. The Hawaiʻi Department of Agriculture quarantine restricts shipping of ʻōhiʻa off Hawaiʻi Island, which means any piece of ʻōhiʻa (log, posts, foliage, etc.) has to be tested free of ROD disease before moving off the island.
We highly recommend that people not move ʻōhiʻa firewood or posts because moving infected wood can indeed spread ROD. The best practice for firewood is to not move ʻōhiʻa wood out of your neighborhood.
If you sell ʻōhiʻa wood, be transparent in your advertising. If you aren't certain of the presence of ROD, say so as a disclaimer. Let buyers or potential buyers know that the current recommendation is to keep ʻōhiʻa wood in your neighborhood.
When cuting ʻōhiʻa, keep saw cuts to a minimum to avoid creating a lot of fine particles. Once wood is bucked up, use an axe to cut the wood into pieces suitable for firewood. If the wood will be cut up at another location, the buyer should be aware of the risk of spreading ROD by cutting at the new location, especially areas of mostly healthy ʻōhiʻa forest.
The fungus that causes ROD can infect trees through injuries or breaks in the tree’s bark. Campers and hikers can prevent the spread of ROD by sanitizing gear, taking care to not injure ʻōhiʻa trees while hiking, and not moving ʻōhiʻa firewood.
Always clean your shoes and gear before and after entering forests. 1. Use a brush to scrap off all dirt and seeds. 2. Spray to coat the bottoms of your shoes with 70% isopropyl (rubbing) alcohol -do the same to hiking poles if you use them.
Many hiking trails through native forest will have ʻōhiʻa roots exposed on the path. To avoid injuring ʻōhiʻa, don’t step on or crush roots.
Don’t mark trails by “blazing” or cutting into trees with a hatchet or machete. Mark trees with paper or flagging if necessary.
Collect or purchase locally-sourced firewood and always inspect it for pests, especially little fire ants, before moving it to another location.
Transport cut wood in a container or at least under a tarp to avoid wood chips or sawdust blowing around.
Burning ROD-infected ʻōhiʻa will kill the disease-causing fungus.
Loggers and millers can help to prevent the spread of ROD by incorporating best practices for handling ʻōhiʻa into the processes for cutting trees, transporting wood, and sanitizing equipment.
When cutting ʻōhiʻa avoid injuring nearby ʻōhiʻa trees, especially if those trees appear healthy and are not intended for harvest. Any break in the bark can allow ROD-causing fungus to enter and cause infection in the trees.
Sawdust can be full of fungal spores. Minimize the amount of sawdust by keeping chainsaws sharp.
If possible avoid harvesting on dry, windy days when sawdust can blow for miles.
Transport logs in a container or covered with a tarp, if possible, to reduce sawdust or wood chips blowing around.
Cut firewood to size on the logging site rather than transporting whole logs and cutting them up and spreading potentially infected sawdust elsewhere.
Prevent the spread of ROD disease by sanitizing equipment and vehicles before and after use.
Clean saws and other tree-cutting tools between sites. Remove wood particles and debris before coating tools with 70% rubbing alcohol spray and allow to sit for 15 seconds before using the tools again.
Wash vehicles with a pressure washer or other high pressure water source to remove all mud and debris, especially from the undercarriage, wheel wells, and tires. Vacuum vehicle interiors where practical. Be careful with ATVs, as pressure washing can damage seals and bearings.
Testing or treating by an approved method is required by law for any ʻōhiʻa wood or post to be shipped off of Hawaiʻi Island. Permitting and testing for off-island shipping is conducted by the Hawaiʻi State Department of Agriculture. ʻŌhiʻa trees can live for months while infected with the fungus that causes ROD, and many trees that did not show symptoms have tested positive. The only way to know if an ʻōhiʻa is infected with Rapid ʻŌhiʻa Death is to test a wood sample.
The fungus that causes ROD will die when wood is heated to over 140 degrees F or dried to less than 15% moisture content. Any ʻōhiʻa lumber or flooring can be used safely after it has been dried in a lumber kiln. Heat treating has been shown to kill the ROD causing fungus in small posts, but there is currently no treatment to kill the fungus in larger posts and the Hawaii Department of Agriculture is still developing approved methods for treating posts.
The fungus that causes Rapid ʻŌhiʻa Death enters trees through wounds. If you need to work with a bulldozer to clear land, there are steps you can take to minimize injuries to ʻōhiʻa trees.
Where possible, choose to work with a bulldozer operator located in your neighborhood or area. Look for someone who operates a small, low-impact machine.
Ask the operator to bring a clean machine to your property or work site to prevent spreading ROD.
Hand clear the path for the bulldozer ahead of time. Trees can be hand-cleared and tree ferns can be transplanted. Use a gravel layer on top of soil to minimize the need for removing soil. Try to place the driveway path where valuable trees are less dense and make the path only as wide as you need to fit your vehicle. Ask the bulldozer operator to give ʻōhiʻa a wide buffer to minimize damage to roots and trunks.
Fresh injuries to ʻōhiʻa can be sprayed with a pruning sealant to prevent ROD-causing fungi from landing on the wounds and causing infection. Be aware that the use of pruning sealant will not guarantee that the tree will be safe from infection.
University of Hawaiʻi at Mānoa College of Tropical Agriculture and Human Resources | USDA ARS Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center | USDA Forest Service Institute of Pacific Islands Forestry | Department of Land and Natural Resources, Division of Forestry and Wildlife | University of Hawaiʻi at Hilo | The Nature Conservancy (TNC) | Hawaiʻi Association of Watershed Partnerships | Coordinating Group on Alien Pest Species (CGAPS) | Big Island, Maui, Molokaʻi, Oʻahu, and Kauaʻi Invasive Species Committees (ISCS) | USFS Region 5 State and Private Forestry | USGS Pacific Island Ecosystems Research Center | Global Airborne Observatory | Hawaiʻi Invasive Species Council | Hawaii Department of Agriculture -Plant Quarantine Branch | Hawaiʻi Volcanoes National Park | Hawaiʻi Tourism Authority |Hawaiʻi Island Seed Bank | Maui Nui Botanical Gardens | National Tropical Botanical Garden | Lyon Arboretum | Laukahi Hawaiʻi Plant Conservation Network