Xylem necrosis (the outer necrotic ring near the cambium) of an Acacia koa stem in transverse section, a symptom of koa wilt disease, caused by Fusarium oxysporum f. sp. koae. The inner area od necrosis in the pith is largely just normal heartwood formation, with some disease necrosis as well.

Necrotic xylem elements in a stem of koa (Acacia koa ) in longitudinal section, associated with koa wilt disease, caused by the plant-pathogenic fungus Fusarium oxysporum f. sp. koae.

Necrotic xylem elements in a stem of Acacia, associated the plant-pathjogenic fungus Fusarium oxysporum f. sp. koae.