Hawaii will again be sharing locally grown avocados with mainland consumers, after an overhaul of federal rules that had restricted the fruits from export to other states for more than two decades.

The U.S. Department of Agriculture finalized new rules Wednesday making it viable for Hawaii farmers to export Sharwil avocados to most states.

The move is expected to greatly expand industry production for one of the state’s smaller, yet highly regarded, crops.

"It’s a great opportunity for us," said Tom Benton, president of the Hawaii Avocado Association. "I believe the market is gigantic out there."

USDA officials estimate that Hawaii avocado growers will export 396,000 pounds of Sharwils a year under the new rules. That’s equivalent to more than half the local industry’s total production of 700,000 pounds in 2011, or about a third of production at a recent peak of 1.2 million pounds in 2007.

Annual sales of the industry, which is mostly on Hawaii island, have been between $500,000 and $800,000 through the past decade, but stand to rise significantly if production expands from export demand.

The new rules allow Sharwils — the state’s dominant commercial variety known for their buttery richness, small seeds, large size and green ripe skin — to be exported to 32 states from November to March, provided certain precautions are taken.

Previously, Hawaii avocado exports had to be fumigated or treated with cold plus fumigation to kill any fruit fly larvae that potentially could devastate fruit farm industries in other states free of fruit flies.

The old treatment process, however, degraded the quality of avocados and made exports unviable.

The new protocol allows exporting untreated Sharwils provided growers maintain fruit fly traps and records, remove fallen fruit from fields, harvest only mature hard fruit with stems attached, and pack fruit within 24 hours in a screened packing facility that prevents fruit fly entry. The USDA also will register and monitor the exporters.

A geographical restriction prohibits Hawaii avocado exports to 17 states including California and Florida, the two dominant avocado-producing states, along with other mostly southern states without cold climates that inhibit fruit fly reproduction.

The new rules represent a reopening of many mainland markets for Hawaii avocado growers, which worked in the 1980s to position Sharwils as an export crop.

Research at the time showed that mature Hawaii Sharwils were an extremely poor host for the oriental fruit fly, and the USDA allowed exports to the mainland in 1991. But the opening was slammed shut in 1992 after fruit fly larvae were found in an avocado that was qualified for export, according to the agency.

The USDA then imposed tight restrictions on Hawaii Sharwils, allowing exports to the mainland only if they were fumigated or treated with cold plus fumigation. Only Alaska was excluded.

Some Hawaii avocado growers regarded the restriction as extreme, unfair and outdated in light of research from the 1990s and rules allowing imports of untreated Hass avocados from Mexico for the past eight years.

After lobbying from the Hawaii Department of Agriculture, the state’s congressional delegation and local growers, the USDA agreed to review its export rules and new studies on fruit fly risk.

Sen. Mazie Hirono noted that relaxed Hawaii avocado export rules had been advocated by the state’s congressional delegation since 1992, and now will benefit local farmers and the local economy.

"The new rule … will finally allow our local producers to sell avocados to the mainland, opening up a number of new markets for these delicious, Hawaii-grown products," she said in a statement.

Benton of the Hawaii Avocado Association said changing the federal rules took a lot of work and time but was worth it. "We’re very pleased with the protocol," he said. "We’re going to have a very competitive crop on the mainland."