The fungus killing Hawaii’s most widespread native forest tree is continuing to make its way across the Big Island but does not appear to have reached any other Hawaiian island yet.

That’s the latest information about the fungal disease causing rapid ohia death from aerial surveys taken across Hawaii last month, state officials said in a news conference Friday at the World Conservation Congress at the Hawai‘i Convention Center.

“We are all scared that it will get to the other islands,” said Philipp Lahaela Walter, state resource and survey forester with the state Division of Forestry and Wildlife.

Officials said rapid ohia death is now afflicting more than 47,000 acres of native forest, up 13,000 acres from surveys conducted at the beginning of the year.

That includes new substantial outbreaks for the first time near Kona.

“Who knows how it got over there?” said Walter, who led helicopter survey teams last month over nearly 1 million acres on six different islands where ohia is known to exist.

“The researchers were as awestruck as us when they saw how widespread it is over there in such a short amount of time. It’s already such a big area, and it’s really scary, actually,” he said.

While some of the increase in infected trees is due to an expanded survey area, he said, much of it is because of new tree mortality, although he added that the new deaths must still be confirmed for rapid ohia death with tests in the laboratory.

There are dozens of other causes of death for ohia, he said, but nothing kills as quickly as rapid ohia death.

The pathogen, in the genus Ceratocystis and of unknown origin, causes the crowns of ohia to turn brown and die within as little as a few days to weeks.

Discovered only two years ago, the fast-spreading disease has killed hundreds of thousands of trees and is threatening native forests and watershed areas on Hawaii island.

Especially alarming to many is the fact that ohia is a cornerstone watershed species in Hawaii and is one of the most cherished and culturally important plants in the islands.

Scientists still don’t know how to stop it, but they’re working on it.

“The spread on the Big Island happened before we even knew what was going on,” said J.B. Friday, extension forester at the University of Hawaii at Hilo.

Similar diseases can spread when beetles bore into infected trees and create an infected sawdust that can be spread by the wind or humans. Scientists suspect this is how rapid ohia death fungus is spreading.

In August the state Department of Agriculture imposed a ban on the export of ohia, its parts and products from Hawaii island without a permit, in an effort to stop the spread.

Aerial surveys suggest that the disease may be on the move in the same direction as the prevailing winds, and officials have warned the public against entering areas with rapid ohia death and possibly carrying out spores on vehicles and footwear.

Rapid ohia death still hasn’t been seen in the northernmost area of the Big Island, going up the Hamakua Coast to Kohala.

Rob Hauff, state protection forester, said state foresters on the island are working with a science team to try out some containment experiments.

“We want to see if we can contain the disease along the Wailuku River, but we need more information to help with a rapid response, should it find its way to another island,” he said.

Scientists are working to plot the rate of mortality, Friday said, and remote sensors have been installed in the forest in hopes of learning mortality rates on a larger, landscape scale.

The U.S. Department of Agriculture has been testing tree samples from other islands and hasn’t found any infected trees.

Elsewhere, monitoring and genetic testing for resistance and the collection and storing of seeds is underway. Aerial surveys of all the islands will continue twice a year, officials said.

Hauff said scientists haven’t seen any particular patterns on the landscape. The disease, he said, has been found at sea level and high elevations, and in wet areas and dry forests.

A strategic response plan, he said, is now in the works to provide direction for what’s needed in research, management and outreach.

Officials have proposed a budget for next year that will see $1.5 million going for research and technology; $945,000 for containment, early detection and rapid response; and $600,000 for public outreach.

Is the spread to the rest of the islands inevitable?

Both Hauff and Friday said they are optimistic the disease can be contained.

“The disease has probably been here longer than we first found it,” Hauff said. “But with DOA’s quarantine, and if we continue to get the message across — don’t move firewood, clean your boots, practice proper sanitation protocols when going from forest to forest — then we certainly have a chance of slowing this down,” he said.

Christy Martin of the Coordinating Group on Alien Pest Species was less optimistic.

“Everything that has been of concern has found a way (to spread),” she said. “It doesn’t mean it’s going to happen today or tomorrow but …”

Officials said the crisis is especially alarming to Native Hawaiians because the tree maintains an important place in the culture. Many hula halau, for example, decided not to use the lei and adornments from the ohia tree at the Merrie Monarch Festival this year in an effort to halt the spread the disease.

“A lot of people are heartbroken,” Friday said.