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Anderson, R. C., and D. E. Gardner. 1998. Investigations of koa (Acacia koa) decline in Hawaiian forests. Abstracts of the 1998 Hawaii Conservation Conference; 30-31 July; Maui. 15.
ABSTRACT
Koa (Acacia koa) is an endemic Hawaiian tree that serves as a keystone species in upland forests. It is second only to 'ohi'a-Iehua (Metrosideros polymorpha) in overall abundance of native overstory trees. Koa stands provide habitat for endemic understory plants, as well as many endemic insects and birds. An unexplained decline resulting in death of koa trees of all age and size classes has been observed over the past several years in both natural forests and agroforestry settings. The decline is often evident in patches, suggesting centers of decline, in which otherwise vigorous trees begin to wilt, develop chlorotic leaves, and die soon after the onset of symptoms. Previous study of the problem indicated that a seedborne vascular wilt fungus (Fusarium oxysporum f. sp. koae), pathogenic to koa seedlings, was associated with seed collected from healthy trees, and may be related to the current decline. In further studies, this fungus has been isolated from roots of dying koa and from healthy trees. Root samples (1-2 cm diameter) were collected from both dying and apparently healthy trees in the Mauna Loa strip areas of Hawai'i Volcanoes National Park. Roots were surface sterilized using standard methods, sectioned, and plated in petri dishes on 2% water agar. Following a short incubation of 3 to 5 days, F. oxysporum f. sp. koae was consistently isolated from the vascular tissue of dying and healthy roots. Greenhouse inoculations of koa seedlings confirmed pathogenicity and virulence of these isolates. The results suggest a close association between koa and this fungus, and a role of the pathogen in shaping koa stand dynamics under environmental and edaphic conditions favorable for disease development.

FULL TEXT
Full text not available for this publication.

HOSTS
Acacia koa - Koa

PATHOGENS
No pathogen information available for this publication.


RELEVANT TO BIOCONTROL
No.

KEY WORDS
Acacia koa.

IMAGES
16_096 -- young dead Koa tree, HAVO 16_096 - young dead Koa tree, HAVO
PATHOGEN: Aspergillus melleus
27_108 -- declining koa tree on Mauna Loa Strip Road 27_108 - declining koa tree on Mauna Loa Strip Road
PATHOGEN: Aspergillus melleus
27_109 -- declining koa tree on Mauna Loa Strip Road 27_109 - declining koa tree on Mauna Loa Strip Road
PATHOGEN: Aspergillus melleus
28_065 -- Fusarium growing from logs from dying koa tree on Mt. Tantalus, Oahu 28_065 - Fusarium growing from logs from dying koa tree on Mt. Tantalus, Oahu
PATHOGEN: Aspergillus melleus
45_080 -- Acacia koa 45_080 - Acacia koa
PATHOGEN: Aspergillus melleus
45_081 -- Acacia koa 45_081 - Acacia koa
PATHOGEN: Aspergillus melleus
45_082 -- Acacia koa 45_082 - Acacia koa
PATHOGEN: Aspergillus melleus

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