KAILUA, KONA, Hawai'i — Even though Hawai'i tropical fruit growers are challenged by inconsistent supplies and lower-priced Asian imports, specialty fruits such as lychee and rambutan have become a multimillion-dollar industry.

On the Big Island, thousands of exotic fruit trees are being planted each year, and as they mature, production is expected to increase. As Hawai'i's pineapple production falls off, exotic fruits have become more common.

"The tropical fruit industry is strong and growing," said Bob Hamilton, a top Big Island fruit grower. "We have good support. We're improving and learning how to get better."

While the state's reputation for fabulous fruit is solid, it may face competition from cheaper foreign imports under a change in the law later this year.

Hamilton and his wife, Susi, have nearly three decades of experience in growing a variety of fruits, including avocado, citrus fruits, rambutan, longan, lychee and starfruit trees that are now being planted around the island.

Each year, the couple sells 50,000 to 60,000 trees for planting, including more than 6,000 rambutan, longan and lychee trees, to Hawai'i farmers through Plant It Hawaii.

"Those are all out there somewhere," said Susi Hamilton.

"Sure, we have a real high standard," Bob Hamilton said. "We continually try to help people grow fruit. I want everyone to be successful."

Hamilton, formerly a custom homebuilder, started his Plant It Hawaii fruit tree nursery in 1979, launched Hula Brothers growing and packing company in 1987, and helped set up the Hawaii Tropical Fruit Growers cooperative in 1991.

The co-op has grown from seven farms in 1991 to more than 40 today. It helps export and market as much as 85 percent of the state's tropical fruit to the Mainland.

Hawai'i's growers of tropical specialty fruit sold an estimated 1.5 million pounds of fruit in 2005, the latest year covered by the National Agricultural Statistics Service. Compared with 2004, higher output was registered for lychee, rambutan and longan, among other fruits.

Farmers, predominantly on the Big Island, produced 400,000 pounds of lychee. Value of sales hit an all-time high of $2.7 million in 2005.

"Fruit from other regions of the world is nowhere near as good as Hawai'i's," Hamilton said. "We've been told that over and over. Hawai'i does have a good name in the fruit market."

Lychee has been a major crop in China for 2,000 years and was introduced into Hawai'i in 1873 and later into Florida. It is slightly bigger than a walnut, with a red skin. It is easy to peel, revealing a firm, translucent, milky-white flesh.

It is typically harvested in June, July and August. This year's crop was a little later than usual.

Longan fruit, known as "dragon's eye," is similar to lychee but smaller, rounder and smoother, with a more aromatic, spicy fruit. It can be harvested year-round.

The golf-ball-size rambutan has long, soft spines, and a sweet, crunchy and juicy flesh. Harvest time varies between October and March.

Although rambutan, longan and other fruits are exported by Hula Brothers and the growers' co-op, lychee remains so popular in Hawai'i the Hamiltons cannot grow enough to export.

That is a common complaint from marketers on the Mainland.

"One of the problems for Mainland retailers is finding consistent supply for items that they'd like to feature and promote," said Tom Tjerandsen, the California-based managing director of the Chilean Fresh Fruit Association.

"They have been tantalized by tropicals and are eager to offer them, but reluctant because the supply has been so tenuous," he said.

Hawai'i farmers may face a new challenge when tropical fruits begin arriving from Thailand this year. A rule change approved last month will allow pineapple, rambutan, lychee, longan and other produce treated with irradiation to kill fruit flies and other pests to be sold in the United States.

Growers in Thailand receive an average of 9 cents a pound for rambutan, compared with about $2.50 a pound in Hawai'i.

Lychee can be held up as an example of a Hawai'i product that has great potential, said Kent Fleming, professor and extension economist for the University of Hawai'i College of Tropical Agriculture and Human Resources.

"It's one of the few bright spots on the export scene," Fleming said. "It's a good product and it has good demand. And anytime we can market to the Mainland, it's a good thing."