Ohia seedlings can survive at least a year without succumbing to Rapid Ohia Death, a new study in the journal Restoration Ecology has found.

Those results offer a “glimmer of hope” in the fight against the fungal disease, the study’s authors say. Rapid Ohia Death, or ROD, is estimated in recent years to have killed at least one million of the native trees in Hawaii, most of them on the Big Island.

The study by the U.S. Geological Survey and the University of Hawaii Hilo found that new Ohia trees will grow despite a heavy presence of the disease in the soil around them.

Questions remain over whether the new trees will survive into maturity. But they at least stand a fighting chance to grow if protected against other lethal threats – namely invasive plants and hoofed animals, said Stephanie Yelenik, a research ecologist with the U.S.G.S. and the study’s co-author.

Dark staining of the sapwood hidden beneath the bark reveals the presence of Rapid Ohia Death. A new study shows seedlings can survive at least a year without getting infected by the disease.

Lisa Keith

“What this tells us is those things that managers know how to deal with are more important in the first year of a seedling’s life than ROD itself,” Yelenik said Friday. “That’s good news.”

Ohia trees help maintain the islands’ water supplies and natural resources, researchers say. They’re also important to Hawaiian cultural traditions.

For the study, researchers in 2018 began planting seedlings at Keaukaha Military Reservation — an area rife with ROD, Yelenik said. They were planted under both healthy and ROD-infected mature Ohia trees.

Some seedlings were protected by fences against pigs and goats while others weren’t, she said. Similarly, some were protected against invasive weeds while others weren’t.

Some 41 of those first 120 seedlings at Keaukaha died — but none of the dead trees tested positive for ROD, according to the study. It found that the trees were six times as likely to die where the weeds were allowed to grow, and three times as likely to die in the unfenced plots.

Researchers will continue to monitor how the seedlings fare and at what point they start showing signs of infection, Yelenik said.

The prevailing theory, she added, is that the disease is largely spread through the trees’ “wounding” — when bark is scraped off and parts are left exposed.

Researchers have already started expanding the seedling study to see how they fare in other areas, including Hawaii Volcanoes National Park and private land near Hilo, Yelenik said. They also aim to plant seedlings in the Big Island’s Kalopa State Recreation Area, she added.

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