Second strain of fungus fingered in rapid ohia death

The bad news just got worse for Hawaii’s indigenous ohia trees.

The trees are under attack by more than one strain of fungus, researchers at the University of Hawaii at Hilo have found.

And humans likely have a large role in spreading the spores, they say.

A research team at the U.S. Department of Agriculture’s Agricultural Research Service in Hilo has discovered that the disease known as rapid ohia death is caused by more than one strain of the fungus Ceratocystis fimbriata, which they suspect can be transferred through trauma to the ohia bark as well as through soil under infected trees.

“We have found evidence of spores in the mud and soil,” said UH-Hilo graduate student Blaine Luiz in a statement released Friday. “Humans can definitely track things very far with vehicles and shoes.”

Luiz is working with the USDA team trying to halt the condition.

Agricultural Research Service research plant pathologist Lisa Keith maintains that human activity contributes most to the spread of rapid ohia death, but they also are examining other possible vectors such as beetles and pigs.

It was previously believed that a single isolate of Ceratocystis fimbriata, a vascular wilt fungus, was the fungus responsible for the growing number of ohia deaths on Hawaii island, but researchers now know that there are two types of the fungus.

Luiz also says that there appear to be slightly different symptoms, which are currently being examined by contrasting the disease cycles of the two types in the laboratory at the Agricultural Research Service facility in Hilo.

Luiz said the best prospect for prevention is to find naturally occurring resistance within the ohia.

Some of the trees in large die-off areas have survived, and Luiz wonders whether there is something about these trees that allows them to withstand the fungi.

The researchers emphasize the importance of not moving any ohia trees, the chopped wood, seedlings or soil near infected trees from one area to another.

“I think we can really curb the transmission,” says Luiz. “I think we’re not too late to stop this spread.”

On the net:

>> Learn about affected areas at the state Department of Agriculture website: hdoa.hawaii.gov.

>> Find updates on the rapid ohia death website of the College of Tropical Agriculture and Human Resources at UH-Manoa: rapidohiadeath.org.