There are a number of pathogens known damage and even kill Ohia trees.
The discovery of Ohia rust in 2005 highlighted the issue of imported pathogens. In an article in LICH Landscape Hawaii Magazine – October/November 2011, Janice Uchida (UH) and Robert D. Hauff (State of Hawaii Department of Land and Natural Resources Division of Forestry and Wildlife) provide more information about this fungus.
‘Serious action for a serious Ohi’a threat’
- Ohi’a rust or guava rust is called Puccinia psidii. This is not ROD-related.
- First found in nursery in 2005, killing ohi’a seedlings
- It has spread to Japan, Australia and other places (article date: 2011), although Hawai’I has one of the many strains
- Ohi’a trees comprise 80% of Hawaii’s native forest (400,000 ha)
- Likely to have been imported
- The headline picture is not described, but looks a bit like a ROD-affected stand
For more information on Piccinia Psidii:
- Wikipedia notes, ‘Puccinia psidii is a rust (a type of plant pathogen) native to Brazil with a very broad host range in the myrtle family (Myrtaceae)’
- Centre for Agriculture and Bioscience International (CABI) datasheet. Useful pictures for identification and good depth of information. According to the map distribution it isn’t present in the UK, however, it looks like Myrtaceae family is susceptible, including Eucalyptus, hence need some awareness!
- Gallery contains three pictures of rust on Ohia. Includes links to papers. Page maintained by James B. Friday.
- Article by J.B.Friday and Faith Campbell, April 2018.
Still need to read through the ‘more information’ links.
Rapid Ohia Death
LICH May/June 2015. Article on ROD,
‘Ceratocystis – wilt of ‘Ohi’a’
by J.B.Friday, Lisa Keith and Flint Hughes. This discusses the ‘newly detected disease [that] has been killing large numbers of ohia trees in forests and residential areas of lower Puna and Hilo on Hawai’i island.’
- it only takes a few weeks to kill trees after symptoms begin to show
- Identified as the vascular wilt fungus Ceratocystis
- 2014: 15,000 forested acres have been affected
- Crowns turn chlorotic then brown
- Disease does not appear to radiate out from infected or dead trees
- Characteristic dark staining of heartwood
- The fruiting bodies of Ceratocystis are called perithecia.
- Hygiene very important to inhibit spread to different areas
Since this article was written two strains of Ceratocystis have been identified, the vector might be wind-blown frass produced by the ambrosia beetle (they make galleries inside the trunks), and it has been discovered on a number of other islands.
This is clearly a cause for concern, and it is not clear what can be done to fix this. Will this rely on natural resistance of a few trees which then seed surrounding areas? Will the forests be allowed to regrow naturally without detrimental impacts of introduced wild animals destroying new plants? It is a problem. There is a great push for residents to plant as many as possible, but I wonder whether increasing the concentrations of plantings will contribute to the spread of this disease. Time will tell!