The spread of ohia wilt on Hawaii Island is much greater than originally feared, with the deadly tree fungus being confirmed in Kona and Hawaii Volcanoes National Park for the first time, according to the state Department of Land and Natural Resources.
Helicopter overflights of 810,000 acres of Big Isle forests between Jan. 11 and Jan. 15 helped confirm that the wilt has spread to approximately 34,000 acres of ohia forest — more than double estimates made in 2014 using satellite imagery of the island, the DLNR announced Friday.
Perhaps most disconcerting about the latest data, said Flint Hughes, a forester with the Institute of Pacific Islands Forestry, were the new locations where ohia wilt, also known as rapid ohia death, appears to have taken hold.
“I’m speaking mainly about Kona,” he said Friday. “We have been on the ground confirming cases of (ohia wilt) mortality over in Kona, but now we’re seeing just how prevalent it is at this time. It’s still not nearly as extensive as what we have been seeing in Puna, but it’s possible for Kona to become that way.
“What’s disappointing is, we had hoped that the fungus would not be as virulent on the Kona side. We were hoping it would experience some environmental constraints, like it was too dry over there, but that doesn’t seem to be the case, unfortunately.”
The disease also was found to be in Hawaiian Ocean View Estates, which was particularly surprising, Hughes said.
“It’s very dry and very open in Ocean View. That was a surprise, and a disappointment,” he said. “Because if it can survive there, it’s a good indicator that (rapid ohia death) is capable of handling a lot of the environmental conditions on the Big Island. We’re concerned that there may not be too many places where ohia is growing and where (the disease) can’t survive. We wonder if those places even exist.”
Ohia forests cover approximately 865,000 acres of land across the state and are considered the primary species providing habitat for countless plants, animals and invertebrates, according to the DLNR. They make up about 75 percent of Hawaii native forests, Hughes added. These forests also protect watersheds that provide significant agriculture and drinking water across the state.
Philipp LaHaela Walter, the state resource and survey forester for the DLNR Division of Forestry and Wildlife, said the recent survey used two surveyors at a time, flying a total of 8.5 hours over state, federal and private lands covering about two-thirds of the Big Island’s ohia forests.
“Our next steps are to cover the rest of the ohia forests with follow-up flights and to ground-truth the aerial operation,” he said. “One of our priorities will be to double-check the Kohala area, where rapid ohia death may have been detected for the first time by our aerial survey.”
The DLNR also announced that its survey confirmed the presence of rapid ohia death within Hawaii Volcanoes National Park for the first time.
“It’s sad but not unexpected that we have a confirmed case of rapid ohia death in Hawaii Volcanoes National Park,” said Cindy Orlando, the park’s superintendent. “We are very concerned about the impacts to our cherished ohia that thrives throughout the park, and we will continue to implement the stringent measures developed by our interagency partners to prevent the spread of this devastating disease. We will also continue to sample trees throughout the park.”
The disease was first noticed in Puna forests around 2010. Four years later, scientists with the U.S. Department of Agriculture’s Daniel K. Inouye Agriculture Research Service lab in Hilo positively identified the cause of the disease as a new strain of the fungus Ceratocystis fimbriata, which has been known for decades as a pathogen of the sweet potato.
Observations show that the disease can kill between 50 and 90 percent of the ohia trees in a heavily infested area.
Scientists think its rapid spread around the island likely has been helped by hitching a ride on people, vehicles, equipment, ohia trees and products made from them. The state Board of Agriculture placed a quarantine on ohia in August, restricting all movement of ohia trees and their products to the other Hawaiian Islands.
“We know that the state Department of Agriculture’s moratorium on the transport and shipment of ohia plants and parts is having a positive effect on curbing the spread,” said J.B. Friday, an extension forester with the University of Hawaii College of Tropical Agriculture and Human Resources. “It’s impossible to determine whether the ban on ohia shipping is 100 percent effective, and that’s why we are trying to get the word out to all forest users, nurseries and lei makers that rapid ohia death is fast killing what is considered one of the most important forest trees in Hawaii.”
Research into treatments for the rapid ohia death fungus continues at the USDA Agricultural Research Service lab in Hilo. Investigation into how it spreads also is being conducted, with potential culprits being insects, underground via roots, on small wood or dust particles, on clothing and shoes, and possibly on animals. Ultimately, scientists hope by identifying what is spreading the fungus, they’ll be able to mitigate its devastating impacts.
Meanwhile, four bills seeking funding to fight rapid ohia death are currently working their way through the state Legislature. They include Senate Bills 3047 and 2271, and House Bills 2675 and 1597.
For more information, visit rapidohiadeath.org.
Email Colin M. Stewart at cstewart@hawaiitribune-herald.com.
