Under new U.S. Department of Agriculture rules that took effect this month, Hawai'i sweet potato growers now can use irradiation as an alternative to fumigation to treat their crop for insects before they are shipped to other states. Previously growers on the Big Island, where there is no fumigation of sweet potatoes, would have to ship their product to Honolulu, where it would undergo fumigation.

The trip sometimes tacked on an additional three to four days to prepare the vegetable for export, said Lyle Wong, head of the state Department of Agriculture's plant industry division. The delay, coupled with other fumigation costs, made it difficult to sell Hawai'i sweet potatoes to certain markets, he said.

Irradiation "gives the shippers the flexibility to meet specific market demands," Wong said.

State officials hope the change will help drive up sales of local sweet potatoes. In 2001, the most recent year for which data is available, farm-level sales of sweet potatoes fell 40 percent to $900,000. Most of that crop is consumed in-state, according to the state.

Sweet potatoes are grown mainly on the Big Island, Maui and Moloka'i. However, the Big Island is the only market where fumigation is not an option, Wong said. The sweet potatoes will still need to meet other criteria, including inspection and packaging requirements.

Irradiation is commonly used to treat Hawai'i fruits and vegetables such as bell peppers, lychee, mangoes, papaya, pineapple and tomatoes before they are exported.

Wong said consumers increasingly are accepting irradiated foods.

"Most of the Mainland markets are accepting it, and it's not an issue," he said.