The rapidly spreading fungus currently posing a threat to Hawaii's native forests might be the result of ambrosia beetles taking control of dead ohia trees. The disease has taken out thousands of the trees thus far, posing dangers to the Big Island's water supply as well as its endangered native bird populations.
The root of the cause is likely in the dust that ambrosia beetles spread, which can travel miles in the wind and lead to the rapid spread of the disease. James Friday, a University of Hawaii forester, believes that the disease - ohia death - likely gets picked up in these dust clouds and makes its way around the island. Thus far, it has affected 35,000 acres of forest over the course of a few years.
"That means it's going to be harder to stop," Friday said. "We can have some control of people going in and out of the forest, but we haven't much control over what blows in the wind."
The exact cause of the spread has yet to be revealed, but scientists are urging property owners to cut down dead trees, contain dust and protect their wood in order to prevent infestation. Hikers and forest workers are being told to ensure that their clothes, tools and shoes are clean when leaving forests to prevent the spread of the disease, which can easily attach to these items through the adhesive pores of the fungus.
The disease has made its way to numerous areas of the island including Puna and Hawaii Volcanoes National Park and shows no sign of slowing down. It works by invading the water circulation system in the ohia tree trunks and kills up to 90 percent of invaded trees.
"The spread of the infection has been downwind," Friday said. "We'd like to get the dead trees on the ground and covered up, particularly in new, critical areas. But controlling beetles is hard. There are so many of them. We're not going to be spreading insecticide across the forests."
Lisa Keith, a research plant pathologist with the U.S. Department of Agriculture in Hilo, says that scientists are currently searching for the source of the disease, although comparisons to the worldwide disease database have yielded no results thus far.
"We are doing molecular analysis of the ohia fungus with other similar strains, trying to figure out how the pathogen got to Hawaii and what plant material it might have come in on," she said. "The fungus might have come in on some nursery plants, certain changes might have occurred, and a new very susceptible host - ohia - became infected. We are also trying to figure out if other agricultural crops might be vulnerable to the disease."