Hawaii Invasive Species Council

Ceratocystis huliohia and Ceratocystis lukuohia

What is ROD? Rapid ʻŌhiʻa Death is a new fungal pathogen, that attacks and can quickly kill ʻōhiʻa trees (Metrosideros polymorpha). The disease has been recognized as two distinct species, Ceratocystis huliohia (ROD canker disease) and C. lukuohia (ROD wilt disease), with significantly different disease behavior– although both ultimately lead to tree mortality. It was first identified on Hawaii Island in 2014. ʻŌhiʻa is endemic to Hawaii and comprises approximately 80% of Hawaii’s native forests. It is a keystone species in the forest, and its loss will negatively impact watersheds, cultural tradition, natural resources, wildlife, and way of life in the Hawaiian Islands.

 

 

 

 

 

 

 

 

 

 

Photo credit above: JB Friday 

C. huliohia distribution (left), C. lukuohia distribution (right):

 

 

 

 

 

 

 

 

 

DESCRIPTION:

• Disease symptoms begin with wilting and yellowing of leaves at the end of branches.
• Symptoms of ROD include rapid browning of crowns, crowns of healthy trees browning in days to weeks is a typical symptom. (See more photos)
• Wood beneath bark will show dark staining of sapwood, this can produce a fruity smell.
• The fungus attacks the vascular system of the plant, which is the system that allows for transport of water, minerals and byproducts of photosynthesis to travel throughout the plant. When this system is blocked, the plant rapidly wilts and dies. 
• “The presence of ROD can only be determined by sampling and testing the sapwood. ROD grows inside the tree, not visible on leaves or bark.” (OISC)
• “Trees within a given stand die in a haphazard pattern; the disease does not appear to radiate out directly from infected or dead trees.” (OISC)
• One way that ROD spreads is through ambrosia beetles, they spread the disease by burrowing galleries into the tree and spreading infected frass. “Frass is the sawdust and woody droppings produced by ambrosia beetles and other wood-boring insects when they bore into and colonize trees.” (UH)

IMPACTS

• Full grown mature trees can rapidly die within weeks to days after infection.
• Loss of ʻōhiʻa leads to breakdown of ecosystems, ʻōhiʻa supports and creates habitat and sustenance for many birds, insects, and understory plants. 
• “The mortality rate for ROD infected trees is 100%.” (OISC)
• Loss of ʻōhiʻa will lead to a decrease in the recharge of our watersheds, ʻōhiʻa is one of the most efficient trees for collecting rainwater and mist and transferring it down into our aquifers to become drinking water. 
• Loss of ʻōhiʻa has a negative impact of Hawaiʻi’s culture, being an important plant in moʻolelo (story), lei, hula, and in countless other spaces. 

ERADICATION & CONTROL METHODS:

• Currently, there is no cure for trees that have been infected by the disease, due to this fact, early detection and prevention is key.
• Avoiding injuries to ʻōhiʻa is the best way to prevent the disease from spreading. “Keep lawnmowers, weed trimmers, and pruning saws away from ʻōhiʻa trees. Step over or around ʻōhiʻa roots while hiking.” (CTAHR)
• Don’t spread ROD, brush all soil and debris off of shoes, tools and equipment. After brushing, spray down after with 70% isopropyl rubbing alcohol. Allow rubbing alcohol to coat the bottom of shoes for a minimum of 15 seconds before hitting the trail. 
• “There are currently no recommended fungicides (fungus-suppressing chemicals) for treating Rapid ʻŌhiʻa Death.” (CTAHR)
• Researchers are currently looking for ROD resistance trees that may already be present in the environment. Greenhouse trials have given promising results, and field trials are currently occurring. (2024)
• Fencing around forests is an effective method to keep hooved animals out, which spread ROD by damaging trees. (See Interactions Between Feral Animals and Rapid ʻŌhiʻa Death)