Control of firetree (Myrica faya Aiton) with herbicides in Hawaii Volcanoes National Park

Abstract

Firetree is recognized as one of the most serious alien plant problems in Hawaii Volcanoes National Park. The species is capable of invading essentially intact ecosystems and forms dense, monotypic stands with little or no ground cover. Because it is a nitrogen-fixer, firetree is able to occupy nutrient-poor recent volcanic substrates, where its litter adds four times more nitrogen to the soil than is derived from all other natural nitrogen sources. Added nitrogen alters the nutrient balance of invaded ecosystems and may encourage the invasion of other alien plants that would not otherwise be able to thrive in nitrogen-poor Hawaiian soils. As of 1989, firetree was controlled in approximately 5,460 ha (13,490 a) of the Park with the herbicide Tordon. Tordon is not an ideal herbicide for use in natural areas, because of the possibility of leaching from the roots of treated plants and movement through the soil to nontarget species. Also, Tordon 22K may be removed from sale in the future in Hawai'i. These two problems led to the initiation of research to find an effective herbicide substitute that would be safe to use on firetrees surrounded by native plants.