Koa wilt it starts to produce microconidia, eventually clogging the xylem. Once the Koa tree dies, the fungus invades all tissues and, upon reaching the dead plant surface, sporulates profusely producing macroconidia and chlamydospores. The fungus can survive saprophytically in the soil, as either mycelium or as any of its three spore types mentioned. The chlamydospores, as the resting spores, survive the longest in the soils, usually under cold conditions. Koa trees occupy dry to mesic areas on the islands of Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi in elevations of 80 to 8,000 feet with 0 to 100 inches of rain.
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