Rapid ʻŌhiʻa Death
Wilt of ʻŌhiʻa

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.

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Koa wilt

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. 

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Myrtle rust

Myrtle rust, also called guava rust or ʻōhiʻa rust in Hawaiʻi, is a plant pathogen that has spread from its origin in Latin America to Hawaiʻi, the Pacific, Australia, and New Zealand in the past few years. The fungus has a broad host range, attacking most trees in the myrtle family (Myrtaceae), including guava, Eucalyptus, Eugenia, Melaleuca (paperbark), and Metrosideros (ʻōhiʻa and pohutukawa), and Syzygium (mountain apple and rose apple in Hawaiʻi).

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Koa moth
(Scotorythra paludicola)

A sudden outbreak of the koa looper moth occurred in the Hilo and Hamakua districts of Hawaii Island in 2013. The moth 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 had not been observed on Hawaii Island for 50 years. 

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Myoporum thrips

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 Hawaiʻi. The insects cause gall-like damage in young leaves and may eventually kill the tree.

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Koa Pest & Disease Image Gallery

Koa Pest and Disease Image Gallery, by Dr. Scot Nelson and Dr. J. B. Friday. Nearly 100 digital photos of pests and diseases of koa (Acacia koa Gray) in Hawaii.

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For more information on forest pests and diseases

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

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