Hawaii Agriculture Research Center (HARC)


Koa Wilt Alert

HARC's Approach to Forestry Research

The vision for forestry in Hawaii is to build an industry that is sustainable, provides for economic development through value-added products, enriches the community by creating new jobs, and enhances the environment through sound conservation practices. It is expected that a variety of forestry segments will be encompassed ranging from short rotation trees for wood chips and related products, to medium and long rotation trees for solid wood production and high value fine hard woods. Research to advance Hawaii's forestry must address the particular needs of each segment as well as those issues that span all segments.

A large commercial eucalyptus planting was initiated on the island of Hawaii. There is also interest in planting commercial stands of the Hawaiian endemic, high-value hardwood tree, Acacia koa (koa). Both eucalyptus and koa require considerable improvement for yield and quality, including the selection for elite seed sources and clones best adapted to Hawaii's highly variable potential planting sites. Likewise, improvement of cultural practices for tree production will also improve yield and quality of harvested trees.

Genetic improvement, silviculture practices and tree measurement, and evaluation of wood quality is needed for selection and improvement of each forestry segment.

Summary of HARC research accomplished to date

Industry segment

Genetic improvement

Tree growth and yield

Evaluation of wood properties

Wood chips, oriented strand board, etc.

Initial provenance screening for several species of eucalyptus; clonal testing in progress

Yield obtained from species and provenance tests

Moisture content and wood density at species level

Solid wood

Initial provenance screening for eucalyptus

Early growth measurements on provenance tests


Fine hard woods

Family screening of koa

Starting silviculture experiments now

Developed a guide to wood properties

Areas of needed research which span all segments are:

- Land preparation, weed control, nutrition, soil conservation
- Forest diseases and pests
- Forestry, including physiology, and environmental issues

Thus far, some attention has been given to land preparation and physiology. It's clear that much research needs to be done in all of the categories shown above. There is also need to investigate covercrops for erosion control and interest in non-timber forest crops which would generate income in the years before tree harvest begins. HARC initiated several research projects to begin filling some of these gaps according to what can reasonably be achieved under the present circumstances, the most immediate needs, and the available sources of funding.

Acacia koa Research

Acacia koa is a Hawaiian endemic hardwood species highly prized for its quality as a craft and furniture-making wood. The natural range of Acacia koa has been greatly reduced owing to logging and land clearing for agricultural production and cattle grazing. Presently, the demand for Acacia koa wood may exceed the sustainable supply. This has resulted in shortages and significant increases in price.

Since 1994, over 200 families of Acacia koa have been grown at the Hawaii Agriculture Research Center (HARC) Maunawili Substation in cooperation with Dr. James L. Brewbaker of the University of Hawaii. Another koa evaluation site is maintained at the University's Hamakua Research Station on Hawaii island (elevation 1900 feet). These koa plantings and others on Maui and Oahu represent well-mapped collections from six Hawaiian islands. Wide genetic variation exists in the rate of growth and tree form, with a large number of families that are strongly arboreal, erect and with limited lateral branching.

The primary objectives for evaluating koa seed sources are to record the variation in tree growth and form between koa families from diverse collection sites, identify quality seed sources for reforestation, and select the best trees and seed sources for further testing. The plots are also maintained for subsequent silvicultural management tests

It is desirable to identify a low elevation koa which is resistant to the pests encountered at that level. Coffee twig borer attack of the koa trials at Maunawili Substation is a serious problem. The borer is not a problem at the koa progeny trials at Hamakua Research Station.

Currently, there are few recommended silvicultural practices established for the management of Acacia koa. When elite seedlings are combined with correct establishment and maintenance practices, the highest yield potential is realized. The cooperative trials seek to determine the type and amount of silvicultural practices required to establish the koa plantings; maintain high rates of growth; and ensure high quality timber.

Koa is a self-incompatible species. Methods are being developed to test the koa breeding system which will help us design a breeding plan for Acacia koa. The work is expected to lead to the development of well adapted low elevation koa progeny which are tolerant borer insects and fungus disease.

Eucalyptus Research

Commercial hardwood operations utilizing Eucalyptus spp. (eucalyptus) are being planted on former sugarcane land on Hawaii Island. About 25,000 acres are scheduled for planting over the next several years. Many other companies from around the world have also been seriously investigating the possibility of starting operations growing eucalyptus in Hawaii. Eucalyptus species have high biomass yield potential and are widely planted in tropical and subtropical locations for production of wood chips for paper pulp and construction boards, and for timber and charcoal. Eucalyptus species identified with high yield potential in Hawaii were E. grandis, E. saligna, and E. urophylla. Hybrids of E. grandis and E. urophylla were found to be productive in Hawaii both as clones and as seedling trees.

With the current development of commercial eucalyptus-based forestry on the island of Hawaii, there is a need to improve yield and quality through the selection of superior individual plants, or by initiating a breeding program. Rapid gain in the yield of eucalyptus has been obtained elsewhere, at a relatively low cost, based on the selection and cloning of elite cultivars from seedlings of introduced species and families. Further increase in yield, disease and insect resistance, and fiber quality would be expected, although at a much higher cost, from the introduction of a wide genetic base followed by the development of a well-designed breeding and selection program.

A number of pathogens potentially damaging to eucalyptus have been reported in Hawaii. Others, known to be serious in other countries, have not yet appeared. As eucalyptus plantings increase, it is likely that disease problems will also increase and may eventually require establishment of control measures. Therefore, surveillance of diseases should be undertaken to identify current diseases and potential problems before they become widespread and also to help in clonal selection, planting site selection and establishment of cultural practices in regard to disease control.

HARC's strategy for the improvement of eucalyptus yield and wood quality is based on the introduction of species and families from native ranges, evaluation in replicated tests, selection and cloning of exceptional cultivars, and field plot evaluation of the those cultivars. The expected outcome of the project is high-yielding eucalyptus cultivars for commercial planting.

Another, more basic research project, focuses on water-use efficiency (WUE) and the pattern of water use under different moisture conditions. This is an important characteristic in selecting a specific genotype for a given area. The carbon isotope ratio provides an intrinsic estimate of WUE and has the potential to be a screening tool for this characteristic. It can be correlated with growth, water use and photosynthetic gas exchange. This project will identify a suitable range of genetic and environmental variation of carbon isotope composition in leaf tissue, then, a selected genotypic subset will be evaluated under the different moisture regimes for each provenance test site.

Weed control in forestry operations is critical for good establishment and growth of the stand. Several herbicides are currently being tested in small plots in eucalyptus at Hamakua Timber.

Fertilization practices are being evaluated to help design field trials to assess the effectiveness of starter fertilizer and subsequent applications on first-year growth. The trials will be installed in different environments to assess the environment x N effect. The principle nutrient of interest is N, therefore, amounts and timing of N application during the first year will be investigated.

Cover crops for erosion control in forestry plantation development

Forest plantation development is highly mechanized and occurs on coastal mountain slopes where rainfall varies from less than 20 inches to over 200 inches per year. During the period from site preparation to tree canopy closure, young forest plantations are vulnerable to periodic intense rainfall. The effects of intense rainfall were found to be mitigated by the use of ground covers in sugarcane cultivation on the Hamakua coast. Certain ground covers may provide additional benefits of providing supplemental nitrogen for early tree growth. A 14 entry cover crop screening trial was installed at a test site on the Hamakua coast to test the performance of various ground covers.

Agroforestry and non-timber forest products

Production of high value timber products does not generate revenue until the first harvest, often requiring 20 or more years. The development of non-timber forest products has the potential to off-set negative cash flow, lower risk, and result in greater economic diversity than production of a single product. However, developing multiple product forest cropping systems are complex and require enhanced scientific understanding and management skills. Research on products such as forest mushrooms, ornamental plants, medicinal herbs, etc. is being initiated at HARC's Maunawili Substation.

Hawaii Agriculture Research Center (HARC)
99-193 Aiea Heights Drive, Suite 300, Aiea, Hawaii 96701-3911
Telephone: (808) 487-5561 Fax: (808) 486-5020
For more information contact Nick Dudley
phone: (808) 486-5334, e-mail: [email protected]
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