Koa wilt They are a dominant forest species. Koa wilt has been found on the islands of Kauaʻi, Oʻahu, Maui, and Hawaiʻi. Most diseased trees are found at elevations below 3,000 feet. However, it has also been observed at elevations as high as 7,000 feet. Fusarium, the primary cause of Koa wilt, May be found in a variety of environments but thrives with the high temperatures and moist soils of Hawaii. It survives in the soil. "F. oxysporum" is a soil-borne pathogen, and currently sanitation, controlling the initial inoculum, is the best means to control it. One should avoid bringing infected soil
Acacia koa there are few koa remaining which are both large and straight enough to do so today. In areas where cattle are present, koa regeneration is almost completely suppressed. However, if the cattle are removed, koa are among the few native Hawaiian plants able to germinate in grassland, and can be instrumental in restoring native forest. It is often possible to begin reforestation in a pasture by disk harrowing the soil, as this scarifies seeds in the soil and encourages large numbers of koa to germinate. Experiments at the Hakalau Forest National Wildlife Refuge have shown that ōhia lehua ("Metrosideros polymorpha")