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Aggressive form of tree-killing disease found on Kauai

December 24, 2018

LIHUE, Hawaii (AP) — Scientists have discovered on Kauai the more aggressive form of a fungal pathogen that kills trees native to Hawaii.

Lab results confirmed last week the more aggressive strain of rapid ohia death, which has affected more than 210 square miles (546 square kilometers) of Big Island forest since it was discovered more than four years ago.

Scientists at the U.S. Department of Agriculture have identified two different species of rapid ohia death, Ceratocystis lukuohia and Ceratocystis huliohia. The less aggressive form, Ceratocystis huliohia, was found for the first time on Kauai earlier this year.

The more aggressive form was recently found in three trees behind Kalalea Mountain. Rapid ohia death has now been discovered at four locations on the island since May.

“This is obviously news we didn’t want to hear,” said Sheri Mann, Kauai district manager for the state Division of Forestry and Wildlife. “But within a day of learning the news, we scheduled a helicopter to conduct more digital mobile sketch mapping to identify any additional symptomatic trees.”

The mapping was followed by drone surveys conducted by the University of Hawaii and acquiring more samples to “determine the severity and distribution of the outbreak,” Mann said.

All the leaves on the three trees had browned, standing out in the green forests and leading to scientists taking samples earlier this month. The samples were tested in a U.S. Department of Agriculture lab in Hilo, producing positive results for the more aggressive strain.

“The pathogen enters the tree through a wound; be it a broken limb, twig or, perhaps, a scuffed up exposed root,” said James Friday, the extension forester with the University of Hawaii. “Whereas C. huliohia may take months to years to kill an ohia tree, C. lukuohia can kill a tree within weeks.”

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