Gardner, D. E. 1978. A seedling disease of koa caused by Fusarium oxysporum. Phytopathology News 12:190-191.
ABSTRACT
Koa (Acacia koa) seedlings grown from seeds in the greenhouse in soil taken from a natural koa habitat within Hawaii Volcanoes National Park (HVNP) exhibited symptoms typical of those of a vascular wilt disease. A Fusarium sp., identified as oxysporum, was consistently isolated from diseased plant root and stem sections plated on water agar (WA). Fifty seven percent of koa seedlings inoculated by dipping roots into conidial suspensions, and incubated with the roots suspended in water at 27-28 C, died or developed severe wilt symptoms. As evidence that the fungus is seed-borne, disease development was also observed among 86% of noninoculated seedlings from certain seed collections grown in sterilized soil or vermiculite. The fungus was isolated from root and stem sections of each inoculated or noninoculated wilted seedling. Approximately 10% of a wide sampling of nongerminated seeds plated on WA yielded F. oxysporum. Similarly, F. oxysporum cultures were obtained from stem sections of wilted noninoculated seedlings, and from seeds, of A. confusa and A. koaia. Seeds of these species were collected with HVNP, and from the Acacia koaia Tree Sanctuary on the island of Hawaii, respectively.
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