Survey: Rapid ‘Ōhi‘a Death More Widespread Than Previously Thought

Recent aerial surveys of Hawaii Island forests showed that a fungal infestation of ‘ōhi‘a trees is much greater than earlier thought. Using a helicopter and specialized survey equipment, crews flew over the area and used satellite imagery to estimate the extent of the disease. Officials say that pending ground verification, new estimates show the infection has now spread to some 34,000 acres on the Big Island of Hawai‘i.

‘Ōhi‘a forests cover more than 800,000 acres on the island, and are considered the primary species providing habitat for countless plants, animals and invertebrates. State officials say the trees are also key to protecting watersheds that provide a significant amount of drinking water across the state.

Philipp LaHaela Walter, the State Resource and Survey Forester for the DLNR Division of Forestry and Wildlife commented in a department press release saying, “We used two surveyors at a time and flew a total of 8 ½ hours over state, federal and private lands covering about two-thirds of the Big Islands’s ‘ōhi‘a forests. Our next steps are to cover the rest of the ‘ōhi‘a forests with follow-up flights and to ground-truth the aerial operation. One of our priorities will be to double-check the Kohala area, where Rapid ‘Ōhi‘a Death may have been detected for the first time by our aerial survey.”

The survey was conducted by a team of experts from DLNR/DOFAW, the US Department of Agriculture Forest Service, the Big Island Invasive Species Committee and the National Park Service/Hawai‘i Volcanoes National Park. The University of Hawai‘i Cooperative Extension Service and the USDA Agricultural Research Service also assisted with planning.

State officials say the pathogen that causes the disease was identified in 2014 by USDA researchers.  Research into treatments for the particular fungus that causes Rapid ‘Ōhi‘a Death continues at the USDA Agricultural Research Service lab in Hilo.

DLNR officials say investigation into how it spreads is also being conducted with potential culprits being: insects, underground via roots, on small wood or dust particles, on clothing and shoes, and possibly on animals. Ultimately scientists hope that by identifying what is spreading the fungus they’ll be able to mitigate its devastating impacts.

Dr. Flint Hughes, with the USDA Forest Service commented, “Unfortunately Rapid ‘Ōhi‘a Death is spreading much quicker than we had hoped. The aerial surveyors noted ‘ōhi‘a trees with no leaves or brown leaves, likely impacted by the disease; as well as ‘ōhi‘a trees which have been dead for a longer time and those that have been affected by either drought or VOG. It’s important that we differentiate the causes of tree deaths and continue to carefully and closely monitor the spread of Rapid ‘Ōhi‘a Death to aid in reducing its spread on Hawai‘i Island and around the state.”

“It’s sad but not unexpected that we have a confirmed case of Rapid ‘Ōhi‘a Death in Hawai‘i Volcanoes National Park,” said Park Superintendent Cindy Orlando. “We are very concerned about the impacts to our cherished ‘ōhi‘a that thrives throughout the park, and we will continue to implement the stringent measures developed by our interagency partners to prevent the spread of this devastating disease. We will also continue to sample trees throughout the park,” Orlando said.

Dr. J.B. Friday, the extension forester with the UH College of Tropical Agriculture & Human Resources Cooperative Extension Service explained, “We know that the state Department of Agriculture’s moratorium on the transport and shipment of ‘ōhi‘a plants and parts is having a positive effect on curbing the spread. It’s impossible to determine whether the ban on ‘ōhi‘a shipping is 100% effective and that’s why we are trying to get the word out to all forest users, nurseries, and lei makers that Rapid ‘Ōhi‘a Death is fast killing what is considered one of the most important forest trees in Hawai‘i.”

Ohia wilt. Image credit UH-CTAHR/ J. B. Friday.

Rapid ‘Ōhi‘a Death. Photo courtesy: DLNR.

Rapid ‘Ōhi‘a Death. Photo courtesy: DLNR.

Rapid ‘Ōhi‘a Death. Photo courtesy: DLNR.

Ohia wilt. Image credit UH-CTAHR/ J. B. Friday.