Koa (Acacia koa) is the premier native hardwood of Hawai‘i and a dominant forest species. It provides endangered species habitat, watershed protection, and most of the timber for Hawaii's forest industry. Hawai‘i's forest industry currently relies on harvesting old-growth koa trees from remnant natural forests, and the current supply does not meet the demand.
Recent land-use changes have led to opportunities and demand to reforest large areas of degraded land with koa. GIS analysis suggests that there are potentially >110,000 acres available for koa reforestation on Hawai‘i Island alone; these are areas currently in alien grasses from 750-1000 m elevation that receive >1000 mm rainfall. However, koa wilt, a fungal disease caused by Fusarium oxysporum, prevents seedling establishment at low to mid elevations where koa is most productive and where there is a surplus of fallow land. To encourage planting and improve the profitability of koa forestry, landowners need a source of improved koa seeds and seedlings selected for wilt-resistance and high quality (i.e., excellent growth, form, wood quality, and pest-resistance). From decades of previous work, we now have the tools to efficiently screen high-quality koa trees for wilt-resistance. The next step is to establish and manage a network of seed orchards of selected trees adapted to environmental conditions across Hawai‘i's ecoregions. This will supply improved koa seeds for forestry and restoration.
Hawai‘i Agriculture Research Center (HARC), the University of Hawai‘i (UH), Tropical HTIRC and USDA Forest Service will collaborate to 1) locate and collect seeds from high-quality trees and screen them for disease resistance, 2) expand and support a network of seed orchards to produce improved koa seeds, and 3) provide educational/extension services to landowners for effective use of improved seed and plantation management. Our long-term goal is to provide improved koa seeds and seedlings to landowners, supporting sustainable forestry, restoration, and conservation in Hawai‘i and increasing economic benefits and ecosystem services from forests. Our objectives are to 1) locate and collect seeds from high-quality trees across ecoregions in Hawai‘i and screen them for wilt-resistance, 2) establish and manage production seed orchards of these selected koa trees, and 3) develop extension services for the best use of improved koa. Our short-term goal is the establishment of new seed orchards that will provide increased production and use of improved, wilt-resistant koa in reforestation. Our long-term vision is to see significant areas of degraded lands reforested with improved koa, providing important ecosystem services and a sustainable supply of koa timber for Hawai‘i's forest industry.
To support sustainable koa forestry, we will:
- Identify wilt-resistant koa families and high-quality trees. HARC and UH will collect seed from wilt-resistant koa populations, existing progeny trials, and selected trees with superior growth, form, wood quality, and pest-resistance from several Hawaiian ecoregions. Leveraging decades of investments into development of the methodologies, HARC will screen seedlings to identify families with high wilt-resistance as candidates for planting in seed orchards. Standardized tree data and locations of trees from which collections are made will be stored in a GIS database.
- Establish and manage improved koa seed orchards. Koa grows across a wide range of environments, with specific genotypes adapted to specific conditions. To preserve this genetic diversity and minimize the likelihood of introduced genotypes contaminating natural populations, HARC and UH will develop and distribute improved koa seeds that are adapted to specific Hawaiian ecoregions to land owners/managers. We will manage and expand the statewide network of ecoregion-specific orchards to maximize seed production using families selected from high-quality trees and wilt-resistance screening trials. Where needed to increase genetic diversity, we will add new families to existing seed orchards. Our state and private partner agencies will provide land for seed orchards.
- Provide information, education, and technology for seed distribution and planting of improved koa. To maximize benefits of improved koa seed orchards, UH extension will provide state and private foresters with information on best management practices for koa forestry, especially about the importance and availability of superior seed and disease tolerance. Management guidelines will include silvicultural recommendations for plantations such as fertilization, thinning, and disease, weed and pest control. To ensure appropriate distribution of improved koa, we will develop protocols for appropriate seed distribution within ecoregions based on environmental tolerance information. Further, we will produce a technical guide and tools for mechanized koa seed processing to improve seed orchard efficiency. These extension services will include web-based information, field trips, workshops, and videos.