Confirmed: Beetles Help Spread Rapid Ohia Death

University of Hawaii researchers have confirmed a culprit in the spread of rapid ohia death.

The fungal blight that’s been killing native ohia trees has infected 135,000 acres of forest on Hawaii Island since 2010. Earlier this year, it emerged on Kauai.

Scientists suspected that its spread has been aided by beetles burrowing into infected trees, and a new paper from the University of Hawaii’s College of Tropical Agriculture and Human Resources confirms that to be the case.

In particular, the college’s research implicated a non-native ambrosia beetle, known as Xyleborus ferrugineus, as one of the causes.

Mark Berthold, a spokesman for the college, said identifying these sources will help researchers come up with ways to contain the plant disease.

“It kind of narrows down the search as far as where it’s spreading to and how it’s spreading,” Berthold told the Tribune-Herald.

To make the connection, researchers studied frass, the sawdust and woody droppings produced by beetles.

They found that 62 percent of the frass contained the fungus’ DNA and 17 percent had viable fungus spores with the potential to spread to healthy trees.

The disease is spread through frass when it comes into contact with a wound on another tree, said Kylle Roy, a former CTAHR researcher who is one of the paper’s authors. She said this beetle is a significant contributor to the spread of the disease because it produces a high amount of frass compared to other species.

Roy, who now works for the U.S. Geological Survey as a geneticist, said research is ongoing in regard to other sources of the disease’s spread, including other beetle species that could be responsible.

“As ROD is getting spread, we are getting new research sites across the island,” she said.

TOM CALLIS Hawaii Tribune-Herald

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