Pests and Diseases
A newly identified disease has killed large numbers of mature ʻōhiʻa trees (Metrosideros polymorpha) in forests and residential areas of the Puna and Hilo Districts of Hawaiʻi Island. Pathogenicity tests conducted by the USDA Agriculture Research Service have determined that the causal agent of the disease is the vascular wilt fungus, Ceratocystis fimbriata.
The Koa Pest and Disease Image Gallery contains nearly 100 digital photos of pests and diseases of koa (Acacia koa Gray) in Hawaii.
Koa wilt is a serious, often fatal disease of the native Hawaiian koa, Acacia koa. Trees affected with the disease rapidly lose their canopies and may die within a few months. Young trees less than 15 years old seem to be affected more often than old trees, and the disease is more often seen on trees planted below 2,500 feet elevation than on trees growing in the forest at higher elevations. Both koa and koaia (Acacia koaia) are susceptible to koa wilt.
Koa moth (Scotorythra paludicola)
A sudden outbreak of the koa looper moth has occurred in the Hilo and Hamakua districts of Hawaii Island since January 2013. The moth has defoliated koa trees (Acacia koa) over tens of thousands of acres of windward, lower elevation forests. Outbreaks of this native insect have occurred regularly on Maui but have not been observed on Hawaii Island for 50 years. Koa trees in good health will probably survive defoliation but with reduced growth. For more information see the Hawaii DLNR Division of Forestry and Wildlife’s koa moth fact sheet. More photos of the moth, caterpillars, damage to leaves, and defoliated koa stands may be found at the koa moth gallery, Will Haines' (UH CTAHR) gallery, and at Karl Magnacca’s (DLNR – DOFAW) on-line gallery.
Haines, WP, ML Heddle, P Welton, and D Rubinoff. 2009. A recent outbreak of the Hawaiian koa moth, Scotorythra paludicola (Lepidoptera: Geometridae), and a review of outbreaks between 1892 and 2003. Pacific Science 63(3) 349-369. doi: 10.2984/049.063.0305
Stein, JD and PG Scowcroft. 1984. Growth and refoliation of koa trees infested by the koa moth, Scotorythra paludicola (Lepidoptera: Geometridae). Pacific Science 34(4): 333-339
Photos courtesy of Karl Magnacca, DLNR-DOFAW
A new rust pathogen has been discovered infecting ohia, eucalyptus, rose apple, and other trees in the Myrtaceae. This fungus could be a serious pest both in native forests and on tree farms and in nurseries.
A new species of thrips (Klambothrips myopori) has recently been discovered attacking naio (Myoporum sandwicense) on Hawaii Island. These insects have been injuring and killing other species of Myoporum in California and have now arrived in Hawaii. The insects cause gall-like damage in young leaves and may eventually kill the tree. They initially were found on cultivated naio papa at resort areas in the South Kohala and North Kona districts and Waikoloa Village and have spread to natural naio populations in Kau and Hawaii Volcanoes National Park and has been found on landscape plantings in Hilo. These thrips only attack naio (Myoporum spp.) To prevent this pest from spreading to neighbor islands, please do not move naio off Hawaii Island. If you find these insects attacking naio on other islands, especially wild populations, please notify Cynthia King, Hawaii Division of Forestry and Wildlife Entomologist, (808) 587-0019, or by email at firstname.lastname@example.org, or call the Hawaii Pest Hotline 643-PEST.
- Hawaii Department of Agriculture New Pest Advisory on Naio Thrips
- Link: Information and photographs of Myoporum thrips from the County of Los Angeles.
- Division of Forestry and Wildlife Naio Thrips Survey
Will the blight end the chestnut?
The farmers rather guess not.
It keeps smoldering at the roots
And sending up new shoots
Until another parasite
Shall come along to end the blight.
- Robert Frost