Koa wilt 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 and iconic Hawaiian trees. The host for Koa wilt is Acacia koa, a tree that is native and endemic
Hawaiian tropical dry forests Hawaiian tropical dry forests The Hawaiian tropical dry forests are a tropical dry broadleaf forest ecoregion in the Hawaiian Islands. They cover an area of on the leeward side of the main islands and the summits of Niihau and Kahoolawe. These forests are either seasonal or sclerophyllous. Annual rainfall is less than and may be as low as ; the rainy season lasts from November to March. Dominant tree species include koa ("Acacia koa"), koaia ("A. koaia"), akoko ("Euphorbia" spp.), ōhia lehua ("Metrosideros polymorpha"), lonomea ("Sapindus oahuensis"), māmane ("Sophora chrysophylla"), loulu ("Pritchardia" spp.), lama ("Diospyros sandwicensis"), olopua ("Nestegis sandwicensis"), wiliwili