Scientists have identified and named the two plant pathogens responsible for rapid ohia death.
The plant disease was first observed in Puna in 2010 and has since been found in 135,000 acres of native forests on Hawaii Island.
By analyzing samples, researchers found that the pathogenic fungi responsible for the disease, tentatively identified as Ceratocystis fimbriata, is actually new strains never seen before. These only attack ohia and were either imported or evolved by interacting with other fungi strains.
While they both have a preference for ohia, neither are closely related — one had DNA similar to Ceratocystis in Asia, while the other has roots in Latin America, according to a news release from the state Department of Land and Natural Resources and University of Hawaii
The new strains were named Ceratocystis huliohia, meaning to change the natural state of ohia, and Certocystis lukuohia, the destroyer of ohia. The agencies said this is the first time Hawaiian names have been given to plant pathogens.
Scientists consulted with Kekuhi Keali‘kanaka‘oleohaililani of the Edith Kanaka‘ole Foundation on naming them.
C. lukuohia is the more deadly variety, from which rapid ohia death gets its name, while damage from C. huliohia might be limited to a branch or two. But both can kill the trees.
Research was done by the U.S. Department of Agriculture’s agricultural research service, UH, University of Pretoria in South Africa and Iowa State University.
J.B. Friday, a UH extension forester who is researching ways to stop the spread of the fungi, said both strains are being labeled as rapid ohia death, also known as ohia wilt, for management purposes.
He said understanding where the disease comes from will help limit its damage to Hawaii Island’s forests.
Knowing there are two strains helps explain what’s being seen in the forests and why not all trees are killed quickly.
“The good news is, first of all, we know what’s going on,” Friday said.
The U.S. Department of Agriculture’s argricultural research service is investigating resistance in different ohia varieties. Last December a University of Hawaii at Hilo student, Blaine Luiz, working with the USDA lab, found some initial indications of resistance in some seedlings of two different varieties of ohia on Hawaii Island, Friday said.
“That was with a few dozen trees,” he said. “We are starting to look at more.”
“It’s set to be a much bigger project,” Friday added.
Email Tom Callis at tcallis@hawaiitribune-herald.com.