Public urged to watch for symptoms of rapid ohia death
The ohia tree is the foundation of the Hawaiian rainforest. Like bones to our body, ohia are essential to the rainforest. Ohia make up 80 percent of the rainforest canopy, filtering light down to other plants and breaking up large raindrops that then fall gently on the forest floor.
Due to the structure of an ohia-dominated rainforest, significantly more water reaches the forests floor to recharge aquifers than in a forest dominated by invasive species like strawberry guava. The native tree’s coarse bark provides surface for ferns and mosses. Its nectar-rich flowers nourish forest birds. But these trees — which exist only in the Hawaiian Islands — are at risk from a phenomenon referred to as rapid ohia death.
Scientists have been working fast to learn as much as they can about the pathogenic fungi that are killing ohia on the island of Hawaii. The first reports of dying ohia came from Puna in 2010. Ohia die for many reasons — but this was different. Trees young and old were succumbing to an unknown disease and the spread didn’t follow a clear pattern — some trees would remain healthy while all around them, their neighbors’ leaves turned brown and died. Then another patch of dying trees would show up miles away. Researchers and scientists scrambled to understand what was happening.
Scientists discovered that rapid ohia death is caused by two new species of the fungus Ceratocystis. The more aggressive of the two fungi spreads and grows in the vascular system of the tree until it cuts off water flow. These particular species were unknown to science until they started killing ohia in Hawaii. Their closest genetic cousins come from Latin America and Asia, and the fungal species attacking ohia likely arrived in Hawaii on imported material.
As of now, ROD is found only on Hawaii island but it has spread fast. From Puna, it spread across 135,000 acres, from Hilo into Volcano and Kona and north to the Hamakua Coast. The most recent detection is in Kohala, a mere 40 miles from Maui.
While the ROD scientists are still working to understand more about the disease, they do know a few key facts that can help stop its spread:
• The fungi are in the woody tissue and can be found up to four years after a tree has died.
• Spores from the fungi are found in the sawdust created by non-native boring beetles. That sawdust can be picked up by the wind and can also land in the surrounding soil and then be carried elsewhere on tires and boots.
• Wounds on healthy trees provide an infection site for the pathogen, much like an injury in your skin offers a place for germs to enter your body.
The Hawaii Department of Agriculture has enacted quarantine measures on the movement of ohia and soil from Hawaii island in hopes of preventing ROD’s spread to other islands. You can help.
First, take precautions to prevent the spread. If you hike or hunt on Hawaii island, clean your gear and boots afterward. Brush off the dirt, then spray with 70 percent isopropyl rubbing alcohol. Purchase locally grown plants to avoid the risk of moving spores in soil or on plants.
Second, take the time to get to know ohia — learn how to recognize this unique Hawaiian species and the stories and cultural values associated with it. Ohia are among the first plants to colonize bare lava flows, and not coincidentally are tied to Pele in legend. Hula practitioners use the tree’s wood, leaves and blossoms both as ornament and instrument in their dance. Ohia nectar is the staple food of many Hawaiian honeycreepers, ‘i’iwi, akohekohe and apapane among them. This tree and the forest it supports is one reason there is water when you turn on the tap. Consider planting one in your yard or adopting one along a trail or road you frequent.
Finally, watch for symptoms of the disease: entire ohia trees or limbs with leaves turning from green to brown within a few days or weeks; leaves will remain intact, frozen in place. If you suspect ROD on Maui, contact the Maui Invasive Species Committee at 573-6472.
Conservation groups across Maui are taking part in efforts to prevent the spread of ROD and detect it early. Crews regularly survey ohia forests by helicopter and collect ohia seeds for storage. Show your ohia love: Find more information at www.rapidohiadeath.org or on Facebook.com/rapidohiadeath.
* Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. “Kia’i Moku,” “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy and quality of life.