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
Lesser koa finch cattle and created ranches in the koa forests, the younger koa trees began to be trampled by the cows. The cows also stripped the leaves off the trees at a faster rate than the leaves normally fell. The older trees were too tall to be defoliated, but their roots were kicked and pulled out, causing them to grow weak and eventually die. With the loss of the native koa trees the last birds began to die off. Finally, the bird was never seen after the year 1891. It is also noted that there were only two confirmed sighting of the