Acacia koaSeedling Wilt Caused byFusarium oxysporumf. sp.koae,f. sp. nov.

Abstract

A wilt disease was observed among koa (A. koa) seedlings in Hawaii [USA]. F. oxysporum was consistently isolated from root and stem tissue of these plants, as well as from wilted A. confusa and A. koaia seedlings. This fungus may be responsible for the premature decline and death of older koa trees established within Hawaii Volcanoes National Park. High wilt percentages among plants grown in a pathogen-free growth medium indicate that the fungus is seedborne. Seed disinfestation procedures did not reduce disease incidence. A new forma specialis, F. oxysporum f. sp. koae f. nov., is proposed for this pathogen.