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A deadly new disease to the Hawaiian Islands known as Rapid Ohia Death has moved swiftly across 34,000 acres of Hawaii Island killing hundreds of thousands of ohia trees. Ohia trees cover more than 1 million acres statewide and are perhaps the most important tree in Hawaii. The ohia tree is fundamental to Hawaii’s watersheds and native forests, which are critical to the sustainability of the island’s source of fresh water.  

A Sense Of Urgency

Scientists are struggling to find a way to curb or eliminate the disease out of fear that, unchecked, the disease likely will kill the entire forested inventory of trees around the state. That, to this writer, seems catastrophic. While I’m a late-comer in joining others in sounding the alarm, and have no claim to any expertise in this field, I do grasp the threat to Hawaii’s water supply and feel compelled to join the other voices in the shout out toward the public’s need to know.

It’s puzzling that the disease is found on other agricultural crops but only seems to attack the ohia tree. Why the disease is fatal to ohia and no other plant is unknown. Equally troubling to the scientific community is how the disease spreads from tree to tree or forest to forest. The scientific name for the disease is Ceratocystis fimbriata; it is a fungus infection. The causes of the deadly infection might be traced to root issues, insects, or rooting animals, but scientists aren’t ruling out other causes. As of this writing, there is no known method of protecting ohia trees from becoming infected.  

Symptoms

The disease seems to have started in East Hawaii Island, in the Puna District. It first appeared about five years ago in a slow start but escalated rapidly. ROD is a fungal disease which affects the vascular system of the tree, preventing water from reaching the stems and leaves which then wilt and die. According to the University of Hawaii at Manoa College of Tropical Agriculture, symptoms of the disease start to show with trees that appear healthy but begin to turn yellowish or brown within days to weeks. Dead leaves remain on the branches for a long time. It doesn’t seem to matter if the tree is young or old. If an infected tree is cut down and a section of the tree removed, the fungus shows up as a dark stain in the sapwood on the outer edges and there may be an over-ripe fruit-like odor. Infected trees do not last long. Many die within two weeks of the initial infection. Many of the trees are in hard-to-access areas where the progress of the disease is difficult to track. Currently the disease has stayed on Hawaii Island and the State Department of Agriculture has set up emergency rules to keep ROD contained.

Origin Of The Species

According to botanical historian-researchers, the ohia here in Hawaii evolved from plants that came from New Zealand or Australia. Over thousands of years of speciation, there occurred a dramatic evolution of the original species, which eventually re-invented itself into the plant now endemic to Hawaii. That is, it’s a species original to the Hawaiian Islands.

Ohia is found on every major island with the exception of Niihau and Kahoolawe. It has widely and vertically proliferated across most climatic zones, from sea level to 10,000 feet; but today it is found mainly at higher elevations.  

Reasons To Care

It bears repeating that we should care about the loss of the ohia forests and the watershed canopy they provide because without them Hawaii’s supply of fresh water would be seriously threatened. But there are other reasons for concern. In the absence of the ohia forests, fast growing weeds and other invasive species will take over the soil, in a hostile vegetation conversion of vast acreages of important mountain-scapes. Ohia has become an important segment of Hawaii’s wood products industry for industrial and household uses, and as a building material for beams and rafters, structural posts and flooring. The wood is of fine, even texture and takes a good polish. It is an important source of fence posts and fuel in high country rural areas. This tree also provides important habitat to native bird species, several of which are endangered. It is one of the most significant plants in Hawaiian culture as stock for carving religious images called kii.  Its flowers and leaf buds are in high demand as culturally important body adornment for hundreds of hula dancers and in a variety of uses in Hawaiian cultural protocol ceremonies.

I recall being emotionally moved in a TEDx Talk by Dr. Pualani Kanaka‘ole Kanahele, a renowned Hawaiian scholar, author and high ranking cultural leader, who cited the cultural significance of the ohia plant. Following the cyclical birth of new land, old mountainside landscapes are buried under rivers of hot molten lava. Having erased everything in its path, the cooling lava begins to resolve itself into an empty, desolate, undulating and ropey landscape called pahoehoe. Then, one day, an ohia sprout suddenly creeps through a crack in the lava.  It is the first tree to appear on the new lava flow. Hawaiian legend has it that the ohia then calls forth the rain, which triggers a remarkable rebirth of the aina (land) marking the beginning of a new cycle of life, and with it, the renewal of the human spirit.

What Can Be Done?

In anticipation of losing much of the ohia forests, there is a prevention and mitigation plan in place. Emergency rules meant to keep the disease from spreading to other islands include sanitation protocols to avoid the spreading of the disease by infected vehicles, shoes and so forth. These protocols are important even in preventing the spread of the infection from one location to another on the same island.

Moving ahead, the Lyon Arboretum is currently working on a seed bank to search for resistant varieties to use in a future reforestation program. For those interested in assisting the effort to address the crises there is a  seeking donations to build up the necessary resources in preparing the long haul to recovery.