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, 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 fungus itself is 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, you would have to submit a sample 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.
No. Cases of ROD have been confirmed on Hawaiʻi Island and Kauaʻi. Both Ceratocystis lukuohia and C. huliohia are present on Hawaiʻi Island, but only C. huliohia has been detected on Kauaʻi.
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 injuring trees, for example with lawnmowers, weed trimmers, or pruning saws will help in avoiding ROD and other fungal diseases.
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 (firstname.lastname@example.org) or the UH ROD educational specialist Corie Yanger (email@example.com). 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 cut the tree down safely and use it as fuel for an imu, fireplace, smokehouse or barbecue on site. If you can’t burn the wood, then you can cut it up and cover it with a tarp, cloth or weed mat to deter boring beetles.
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.
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, Moloka'i, O'ahu, and Kaua'i Invasive Species Committees (ISCS) | USFS Region 5 State and Private Forestry | USGS Pacific Island Ecosystems Research Center | Carnegie Airborne Observatory l Hawai'i Invasive Species Council l Hawaii Department of Agriculture -Plant Quarantine Branch