Rapid ohia death advancing

Rapid ohia death continues to spread on the Big Island, according to data from recent aerial surveys.

Rapid ohia death continues to spread on the Big Island, according to data from recent aerial surveys.

Approximately 47,000 acres of forest now show symptoms of the high-mortality disease, which is caused by a strain of the fungus Ceratocystis fimbriata.

Survey helicopters also flew in January and February of this year, when 38,000 acres were found to be affected.

Part of the reason for the increase in acreage is because the survey area itself was expanded to include more land, said Philipp Lahaela Walter, state resource and survey forester with the state Department of Land and Natural Resource’s Division of Forestry and Wildlife.

But rapid ohia death itself is “definitely spreading,” he said. “We see a big outbreak on the Kona side, just upslope of Kealakekua, which just shocked us, honestly.”

Puna, where outbreaks of rapid ohia death were first noticed, is slowing a bit in ohia die-off.

A tree that is infected by Ceratocystis fimbriata displays yellowing leaves, which then brown and die. Its sapwood displays a telltale dark stain.

“The reason we call this rapid is because the period of time from … manifestation of symptoms to death is quite quick,” said Flint Hughes of the U.S. Department of Agriculture Forest Service.

There is a gap between initial infection and manifestation of symptoms, but researchers are not yet sure how long that is.

Lahaela Walter stressed that trees in the affected areas would need to be sampled by a laboratory to confirm the presence of Ceratocystis fimbriata.

“We can only see symptoms (from the air), but ohia trees die for all kinds of reasons,” he said.

The survey team consisted of DLNR/DOFAW, the Forest Service, National Park Service, and members of state invasive species committees, with additional planning by the University of Hawaii Cooperative Extension Service and the USDA Agricultural Research Service.

Helicopters surveyed forest on Hawaii Island, Oahu, Maui, Molokai, Lanai and Kauai.

Although some dead ohia were found on other islands, they were not confirmed ROD cases.

“At this point, we do believe that the disease is contained on the Big Island for right now,” Lahaela Walter said. “We really hope that this new quarantine is going to help prevent it spreading.”

A temporary quarantine on transport of ohia from Hawaii Island went into effect last summer. The state Board of Agriculture is expected to rule on a permanent quarantine later this month.

The 47,000 acres represents about 9 percent of the island’s surveyed forest.

“There is still a lot of healthy forest out there, and we still need to be active in protecting those large expanses,” Hughes said. “Making sure other trees don’t become vectors — that’s a big part of our strategy.”

“It’s really the public that makes the difference here,” Lahaela Walter said. “We heavily rely on the public, and so far the public has been great and motivated.”

For more information, visit rapidohiadeath.org.

Email Ivy Ashe at iashe@hawaiitribune-herald.com.