A Deadly Fungus Threatens to Wipe Out Native ‘Ōhi‘a on Hawai‘i Island

As if Hawai‘i’s native forests weren’t in enough danger, the ‘ōhi‘a faces a new, deadly fungal foe on a massive scale.

The disease decimates a forest at the outbreak epicenter in the Puna district of Hawai‘i Island.

photos: j.b. friday, university of hawai‘i

Kūpuna tell us the ‘ōhi‘a tree’s purple blossoms of Lāna‘i sprang from an ancient battle.

Today’s ‘ōhi‘a of every color are fighting for their lives: A fungus has already killed more than half the ‘ōhi‘a on 6,000 acres of Hawai‘i Island. That’s just as of last year; infected trees usually die in a matter of weeks, and it takes only two to three years for all ‘ōhi‘a trees in an area to succumb to the fungus. Without a cure, the plague will continue to spread and wipe out ‘ōhi‘a across thousands of acres.

According to legend, Kawelo, ancient kahuna of Lāna‘i, prayed to death Lanikāula, the kahuna from Moloka‘i who had laid curse after curse upon Kawelo’s people. Kawelo burned Lanikāula’s kūkae, or excrement, in a ceremonial fire, spewing deep purple smoke that staned the ‘ōhi‘a trees to create the pōlehua, the famed dark-purple lehua blossom. 

The fungus causes  staining in the sapwood, as seen in this cross-section sample of an infected tree.

But the crisis is not just about ‘ōhi‘a, explains associate specialist from the University of Hawai‘i’s College of Tropical Agriculture and Human Resources, Dr. J.B. Friday. “It’s the birds, the watershed, everything ‘ōhi‘a means to the forest. Other trees may grow in, but they won’t be native. It’ll be all weeds, like in Puna.” ‘Ōhi‘a is often the first native plant to sprout on a fresh lava flow and forms the foundation of diverse native forests and watersheds across the archipelago. After ‘ōhi‘a forests of Lāna‘i disappeared, thorny kiawe, bare dirt and weeds took their place. 

The fungus, Ceratocystis fimbriata, grows inside the tree, choking its ability to take in water and causing the ‘ōhi‘a to wilt, turn shades of yellow or brown and, eventually, die. The origins of this new fungus are still a mystery; scientists analyzed the fungus’ DNA to discover it hasn’t been found anywhere else in the world. Friday suspects a reason for the breakout in east Hawai‘i Island could be due to damage from Hurricane Iselle that made ‘ōhi‘a susceptible. “Hurricane Iselle broke branches, which are like open wounds and can get infected,” he says.

With no cure or treatment, the fungus continues to spread throughout Hawai‘i Island, leaving experts worried it could spread to other large ‘ōhi‘a populations on O‘ahu, Maui, Moloka‘i and Lāna‘i, where ‘ōhi‘a also continues to play a significant role in watersheds, native forests and Native Hawaiian cultural traditions. To slow the fungus’ progression, Friday warns against the transportation of ‘ōhi‘a from infected areas for use as construction material, firewood or seedlings. The fungus has also been found in soil, so those traveling through infected areas should be careful to clean shoes, equipment and vehicles.

Did you know? Hawai‘i boasts more than 10,000 native species. For those living in native forests, ‘ōhi‘a is often a backbone to their ecosystem.

For more information visit ohiawilt.org