HILO — State environmental experts are asking residents to use alternatives to ohia when making holiday wreaths to lower the risk of spreading rapid ohia death.

Ohia is popular in wreaths for its bright red flowers, but picking it risks wounding the tree and further transporting the disease, said Anya Tagawa, outreach and education specialist for the state Department of Land and Natural Resources’ Division of Forestry and Wildlife.

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Researchers are hosting two wreath-making workshops this month to demonstrate how to use alternative native plants to ohia — such as pukiawe, aalii and ohelo — to create wreaths with a similarly festive look. The first wreath-making workshop was Wednesday. The second and final workshop is this Friday.

“It’s a very common thing to do — (ohia) makes festive holiday wreaths,” Tagawa said. “And there’s no ban or regulation not to pick ohia. If you do, we’re recommending only taking the green leaf tips of the ohia plant material because the likelihood of transporting the disease is a lot less than the wooding material. But at the wreath workshops, we show alternative ways to create wreaths that look just as festive for the holiday season.”

ROD was islandwide as of September, when it was detected on a private ranch in North Kohala. Researchers worried at the time the fungus might have arrived via wind-born sawdust material — called frass — produced by the drilling activity of beetles attracted to dead and dying ohia.

They since have determined that might not be the case, said Bill Stormont, service forester for the Division of Forestry and Wildlife.

“Because of the elevation of the site, the ambrosia beetles are not present,” Stormont said. “We’re not seeing any infected trees produce any frass. There’s less concern about air-borne distribution of the inoculum from those.”

Half of roughly 100 trees sampled at the Kohala site tested positive for ROD. Researchers cut seven trees down and now are in a “monitoring phase,” Stormont said.

Stormont said researchers think a “wind event” in January that blew “heavily out of the south up the Kona coast” could have caused wounding and spread the fungus to North Kohala but they’re not yet certain. He said they’re worried about the potential for ROD to spread off-island.

“It’s a strong possibility that was a potential for these trees to get infected but we don’t know enough about this beast just yet to make any definite calls,” Stormont said. “We’re puzzled by this giant leap and the concern is the next 40 miles (from the Kohala infection site) puts us at Maui.”

Stormont also reminds residents that shipping ohia off the island is prohibited without a permit.

ROD also can spread via machinery used for landscaping and building. Homeowners and agencies are advised to clean equipment and to “think twice about the type of activities they’re contracting … and what impact that might have on the ohia trees on a given property,” said Flint Hughes, research ecologist with the U.S. Forest Service.

“Folks hiring operators need to think, ‘Is it worth the work, first of all’ and second, ‘Am I going to be creating a hazardous condition for the trees on my property?’” Hughes said. “Not to mention, it’s having those trees act as sources of inoculum for trees in the general vicinity. So it’s important to take those things into consideration.

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“If we care about ohia and the forest, we need to care for them. And we need to put in the effort to care for them and to be thoughtful about that.”

Email Kirsten Johnson at kjohnson@hawaiitribune-herald.com.