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.
Oʻahu ʻamakihi assigned to "Chlorodrepanis" based on the phylogenetic analysis of mitochondrial and nuclear DNA sequences. It tends to stay in the wetter southern area of Oahu, and in the valley near Wahiawa and Mililani. It can easily be spotted in two major parks, the Honouliuli Preserve, and the Wa'ahila Ridge State Recreation Area. It tends to stay in forest, but has - at least to some extent - adapted to non-native forest types. It will nest and forage in wooded urban areas, but prefers native habitats where koa ("Acacia koa") dominates. It mainly occurs at altitudes above , but in some