Koa wilt trees. Outrigger canoe racing, often in koa canoes, is still a popular and highly competitive sport of cultural significance. Koa wilt Koa wilt is a relatively new disease to Hawaii, discovered in 1980. Koa wilt is caused by a forma specialis of the fungus "Fusarium oxysporum", which is now abundant in Hawaiian soils and infects the native Acacia koa tree, a once-dominant species in the canopy of Hawaiian forests. Fusarium oxysporum f.sp. koae is believed to have been brought into Hawaii on an ornamental acacia plant. Fusarium fungi clog the tree xylem, causing significant wilt and mortality among these beautiful
Metrosideros polymorpha the most common native tree in the Hawaiian Islands, tolerating a wide range of soil conditions, temperature, and rainfall. It grows from sea level right up to the tree line at elevations of and is commonly found in moist and dry forests, high shrublands, and is a colonizer of recent lava flows. It is relatively slow growing. Dominant in cloud forests above , the tree is also common in seasonally wet forests, where it may be dominant or form mixtures with the native "Acacia koa". "Metrosideros polymorpha" may occur as a tall tree or a prostrate shrub, and everything in