• CTAHR’s only large station in koa belt
  
• Elevation 2200 to 2800 ft, 100 acres
  
• Rainfall 75-100 inches, Latosols
  
• First opened in 1962
  
  

Hamakua Research Station has been the home of experiments with koa (Acacia koa Gray) since 1990. New koa trials are planted every year, and focus on:

• Genetic improvement
  
• Improved cultivation practices
  
• Improved disease resistance
  
  

Ongoing Koa Research at Hamakua:

• Evaluation of koa germplasm statewide
  
• Heritability of bole form and quality
  
• Identifying resistance to koa decline
  
• Microbiology of koa (its rhizobia and mycorrhiza)
  
• Seed production of improved varieties
  
  

Koa is Hawaii’s premier high-value hardwood. Its wood is valued for its beauty, color, figure and quality. Deforestation greatly reduced Hawaii’s native stands of koa. Koa decline further reduces stands at low elevations. Continuing deforestation in the tropics enhances the value of koa wood.

In 1990, little was known of koa’s potential as a cultivated plantation tree. Less was known of its genetic diversity. These formed the basis for koa research at Hamakua.

Tree Improvement Research at Hamakua:

Research trials have been planted annually since 1990. Most are trials of koa families derived from single mother trees. About 50 families are grown each year, with two replications of 10-tree plots. Duplicate trials occur on Oahu at Maunawili (>1995) and Opaeula (>1998). More than 500 families have been studied since 1990.

Koa keikis are transplanted at 4 to 5 months. Trees are spaced closely (1 x 1.5m), fertilized and later thinned. Weed growth is minimized. Average heights of the best 25% of these families are summarized below:

Seed Production at Hamakua. Seed sources currently available to Hawaii’s growers produced fewer than 10% quality trees at Hamakua. Thus, it is our intent to breed improved varieties of koa. The first seed orchard was planted in 1999, based on seeds from superior trees or families.

Identification of Disease Resistance at Hamakua. "Koa decline" leads to wilt and death of mature trees, and appears to be due mainly to a fungal disease. Insect borers and pig damage may facilitate the fungal entry. At Hamakua we are identifying koa families with apparent tolerance to this disease, and resistance to common rust of koa leaves.

Conclusions from this Research:

• Koa is a very fast-growing tree
  
• Koa is outcrossing and highly variable
  
• Most koas are poor genetic parents
  
• Koa seeds can be harvested in 4 years
  
• Koa seedlings need "tender loving care", especially in the first year
  
• Koa must be protected carefully from browsing animals and pigs
  
• Koa has serious disease problems that limit it at present to high elevations