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HILO, Hawaii (AP) — A fungal pathogen may be responsible for recent die-offs of beloved Hawaii trees, according to state scientists and tree experts.
For the last five years, native ohia (oh-HEE'-ah) trees have been under attack by what foresters call Rapid Ohia Death, and researchers say the cause may be a fungal pathogen known as Ceratocystis, the Hawaii Tribune Herald (http://bit.ly/1Az4QWT ) reported.
The pathogen has been found before on taro and Okinawan sweet potato. The effects are devastating, University of Hawaii extension forester J.B. Friday said.
"A lot of things can kill ohia," Friday said. "Most commonly, it's people clearing land with a bulldozer. They'll drive over the roots, injuring the roots, and that tree will decline and die over a year or two. . and there's the other usual stuff killing ohia, like the atmosphere — vog (a form of air pollution) or drought — which can take years. . But with Ceratocystis, the tree goes from green to yellow to dead in a matter of two weeks."
The trees die so quickly that they don't have time to drop their leaves, said Flint Hughes, an ecosystems ecologist with the Institute of Pacific Islands Forestry.
Scientists considered various explanations, including some that didn't seem plausible.
"One of them was earthquake activity (damaging roots)," Hughes said. "One of them was some kind of outgassing from subterranean lava, which never really seemed to be that satisfactory of an answer."
In January 2014, Friday brought a cross-sectioned sample of a dead ohia tree trunk to Brian Bush at the University of Hawaii Agricultural Diagnostic Service Center, said Lisa Keith, a research plant pathologist with the Pacific Basin Agricultural Research Center.
"I got this list of the fungi (Bush) found in the sample, and I thought, hmmm, Ceratocystis seems kind of unusual," she said. "It is a well-known pathogen that causes problems in a lot of different hosts."
She performed experiments with the fungus, including inoculating ohia seedlings in a controlled environment. She is confident the pathogen is the culprit, but many questions remain, she said, such as how the fungus spreads, where it came from and why it kills some trees and not others.
The questions will be a focus of research for years, Friday said.
"I think, in the long term, we're going to be working on this project for the next 20 years," he said. "It's like we've opened up this big box, this huge, complicated problem."
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Information from: Hawaii Tribune-Herald, http://www.hawaiitribune-herald.com/
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