Ohia wilt, also known by the more disturbing moniker “rapid ohia death,” so far has claimed hundreds of thousands of Hawaii’s most iconic tree.
Ohia wilt, also known by the more disturbing moniker “rapid ohia death,” so far has claimed hundreds of thousands of Hawaii’s most iconic tree.
Today, the state Department of Land and Natural Resources and its state and federal partners are expected to announce a new awareness campaign tasked with spreading the word about ohia wilt and how Hawaii residents can do their part to slow the disease’s spread.
The pathogen, which first was noticed in Puna in 2010 and first identified in 2014 as the fungus Ceratocystis fimbriata, so far has killed large numbers of mature ohia trees in forests and residential areas of the Puna and Hilo districts of the Big Island. And in the last year, it has continued to spread — being found as far away as Kona.
Recently, the disease was found at the 5,000-foot level along the Wailuku River mauka of Hilo, a particularly disturbing finding, said J.B. Friday, an extension forester with the University of Hawaii College of Tropical Agriculture and Human Resources.
“(On a recent map of the spread), there are spots going all up the Wailuku River, which is bad because water can move (ohia wilt), moving it all the way down the watershed,” he said in a phone interview Tuesday morning.
“We also now have a positive identification in Volcano Village, in Holualoa in Kona, and we have a positive (identification) in Kealakekua. It’s proceeding to spread. But we still have no positives in North Kona, in Kohala and the Hamakua-Kohala side.”
He added that he has a suspicion tests currently being conducted on samples could reveal that ohia wilt has spread to areas in Ka‘u, as well.
“We’re still double-checking that,” he said.
Lisa Keith, with the USDA’s Agriculture Research Service, confirmed later Tuesday that the Ka‘u sample indeed turned up positive for the rapid ohia death fungus.
“We found it in Ka‘u,” she said. “In fact, it’s really easier to say now where it isn’t rather than where it is.”
The disease has the potential to kill ohia trees statewide, with a mortality rate of about 50 percent in infected stands, according to an information page hosted on CTAHR’s website at www2.ctahr.hawaii.edu/forestry/disease/ohia_wilt.html.
Despite the disease’s potential to seriously impact Hawaii’s ohia trees, scientists are making progress in their study of ohia wilt, with some promising leads, Friday said.
“We’ve had a couple of indications of the fungus’ vulnerability,” he said. “For instance, if the wood is dried out enough, (the fungus) will no longer be viable. Or if the temperature drops low enough.”
Keith said she, Friday and USDA Forest Service researcher Flint Hughes have been working to find management techniques and sanitation protocols that can be used to slow the progress of the pathogen, hopefully keeping it from spreading to the other Hawaiian Islands.
“There are strategies that work, and I think at this point that’s what we’re really trying to do is limit its spread,” she said.
Currently, the researchers are testing a fungicide that could be used to treat wood and other plant products from ohia, although a fungicide likely wouldn’t be a large-scale solution for the island’s ohia forests.
Keith added that there is some hope some ohia trees will prove to be naturally resistant to the disease.
“There are trees which are surrounded by ohia wilt, but they have not been infected,” she said. “There have been some newer studies into host resistance. But it’s still too early to tell in the disease cycle process.”
This summer, the state Department of Agriculture approved an interim rule restricting the movement from Hawaii Island of ohia plants and plant parts, including flowers, leaves, seeds, stems, twigs, cuttings, untreated wood, logs, mulch, greenwaste and even the sawdust from boring beetles.
A moratorium on the movement of soil from the Big Island, such as in exports of potted plants, also was supposed to take place in January, but now was pushed back to February as a result of testing that showed the fungus was not showing up in soil used by nurseries, Friday added.
For more information, visit www.rapidohiadeath.org.
Email Colin M. Stewart at cstewart@hawaiitribune-herald.com.
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Five Things You Can Do to Prevent the Spread of Rapid Ohia Death:
• Don’t move ohia: Do not move ohia wood, firewood or posts, especially from an area known to have rapid ohia death. If you don’t know where the wood is from, don’t move it.
• Don’t transport ohia interisland: Comply with the new quarantine rule to help prevent rapid ohia death from spreading. Don’t move ohia plants, wood or other ohia plant parts interisland without a permit.
• Clean your tools: Use only proven cleaning methods — other methods have been tested and they don’t kill the fungus. Tools used for cutting ohia trees (especially infected ones) should be cleaned with 70 percent rubbing alcohol or 10 percent bleach (if using bleach be sure to oil afterwards to prevent corrosion).
• Clean your gear: Clean your shoes and clothing. Decontaminate shoes by dipping the soles in 10 percent bleach or 70 percent rubbing alcohol to kill the rapid ohia death fungus. Other gear can be sprayed with the same proven cleaning solutions. Wash clothing in hot water and detergent.
• Wash your vehicle: Wash the tires and undercarriage of your vehicle with detergent especially after traveling from an area with rapid ohia death and/or if you traveled off-road.