In an effort to combat a fungus that’s ravaging native ohia trees on Hawaii island, state quarantine officials want to put more restrictions on wood that might be infected.

The proposed temporary rule aims to prevent further spread of the pathogen, formally Ceratocystis fimbriata, which disrupts the vascular system of the ohia tree, halting the flow of water.

That stains the crown brown and death follows within weeks. Once infected, a stand of trees can die within three years, scientists say.

By the end of last year, the fungus, also known as ohia wilt, had killed half of the ohia lehua trees on about 6,000 acres from Kalapana to Hilo, ecologists estimate. Flint Hughes, a research ecologist with the U.S. Forest Service, said this year ohia wilt has spread tens of miles, into the Hilo Forest Reserve and along Saddle Road below Hawai‘i Volcanoes National Park.

“We’re seeing a significant spread of the disease,” Hughes said.

The quarantine proposal is slated to go before the state Board of Agriculture on Aug. 25. Details about the interim rule are scheduled to be available for public review Tuesday on the board’s website.  

Under the proposed interim rule, ohia lumber exhibiting symptoms of ohia wilt will not be allowed to be shipped off island.

“Lumber that do not exhibit symptoms of ohia wilt will be allowed for shipment,” said acting Plant Quarantine Manager Amy Takahashi.

Jeff Anderson, owner of Jeff Anderson Saw Milling Services in Ocean View, which sells ohia lumber and poles, said he is unsure how the rule would affect his bottom line.

“I know its going to be tougher,” said Anderson, who’s been in business since 1994.

Takahashi said native forests on all of the Hawaiian Islands are at risk if the fungus spreads from the Big Island. It’s unknown how the fungus reached the island, where the problem arose about five years ago.

So far, the disease has not been reported on other islands.

Ohia lehua, or Metrosideros polymorpha, is culturally important to Native Hawaiians and serves as a foundation for native forests by providing cover for native plant species, including ferns and mosses that capture rain for Hawaii’s watersheds.

“It’s the keystone species in terms of forest development,” Hughes said, noting that ohia trees comprise about 50 percent of the biomass of a native forest.

Researchers say besides showing vascular discoloration or dark staining, infected wood can smell like rotten bananas.

There’s currently no cure for ohia wilt, and fungus from infected wood can remain contagious for longer than a year.

Scientists are continuing to look into the methods in which the fungus spreads. Researchers have determined it spreads in wood, soil and insect excrement. Pigs and beetles also could be vectors, researchers say.

Ohia wood is used for a variety of purposes, including construction, furniture and wood trim. Present in many facets of Hawaiian culture, ohia lehua figures prominently in chants and legends; its blossoms are used as an adornment in hula, and early Hawaiians used the wood to carve images of deities.