Good inspectors know right away what to watch for: coolers, paper boxes, plastic wrapping, strange shapes bundled with the beachwear. Most travelers don't know they're breaking the law, but a few deliberately try to sneak something past.

By midmorning on a recent weekday, inspectors at one station had intercepted three trash bags of contraband. But they weren't out to foil a terrorist plot. They were looking for illegal fruit, plants and meat that could introduce a devastating new species or disease to the Islands' fragile ecosystem.

"Our mission has always been agriculture," said Vernon Harrington, who works with the federal Animal and Plant Health Inspection Service on Hawai'i.

That mission may soon change.

Inspectors who screen foreign visitors, mail and cargo at U.S. ports of entry are being transferred from the U.S. Department of Agriculture to the new U.S. Department of Homeland Security. They will work with customs and immigration agents to tighten border security and prevent terrorists from entering the country, part of the largest federal reorganization since World War II.

Transition teams still are working out details, with the goal of forming the new force by March. But some people inside and outside APHIS, as the service is known, have questions about the wisdom of dividing the agency between the USDA and homeland security.

Agricultural inspectors do not carry weapons or have the power to arrest. They have not been trained in security. Their expertise is in detecting foreign threats to domestic agriculture, a vital function for states vulnerable to outside species.

USDA officer Danielle Kitaoka of the Plant Protection Quarantine Canine unit uses Gator to check bags for fruits, plants or meat brought from overseas at Honolulu International Airport. Richard Ambo • Honolulu Advertiser

Outbreaks can have dramatic consequences. Last year, the United States took extra precautions with imported meat after foot-and-mouth disease led to the destruction of more than 4 million animals in the United Kingdom and $5 billion in food and agriculture losses. Closer to home, Asian long-horned beetles, suspected of hitchhiking from China in wood packing materials, threaten maple and other hardwood trees in New York, New Jersey and Illinois.

Bobby Acord, APHIS administrator in Washington, D.C., said it made sense to fold in some of his inspectors with customs and immigration agents to improve efficiency and create a single foreign inspection force. But he said it was likely each branch would maintain its core functions.

"Agriculture is homeland security," Acord said.

Anthrax attacks sent through the mail last year and reports that some Sept. 11 hijackers looked into using crop-dusting planes increased fears about the safety of the nation's food and water supplies.

Sen. Daniel Akaka, D-Hawai'i, has tried to increase federal preparedness for an agriculture-based terrorist attack. But he failed in an attempt to amend the homeland security bill. Akaka wanted to require the new department to report to Congress about how nonsecurity missions of the 22 merging agencies were being preserved. "I am concerned that Hawai'i's unique agriculture and biosecurity needs will be adversely affected," said Akaka, who voted against the bill.

Some people in Hawai'i's agricultural community also have reservations.

Larry Nakahara, manager of the plant pest control branch at the Hawai'i Department of Agriculture, said the state would be at high risk if inspection priorities swing from agriculture to security.

On the Big Island, for instance, state agriculture officials are battling the nettle caterpillar, a prickly Southeast Asian invader that feeds on palm and grasses, as well as the fire ant, which can cause stings and welts. The Bishop Museum has documented more than 5,000 alien species in the Islands, of which 300 to 500 pose risks to the ecosystem, according to experts.

Nakahara wonders whether the close working relationship between state and federal inspectors will continue once APHIS is split apart.

"Their priorities may change," he said. "What will that do to pest interception from foreign countries?"

In Hawai'i, some 60 percent of APHIS employees will stay with the USDA, while 40 percent will move to homeland security. The homeland security inspectors will screen foreign visitors arriving in Hawai'i, while USDA inspectors will continue doing pre-departure searches of travelers leaving for the Mainland.

Susan Matsushima, president of Alluvion, a wholesale nursery in Hale'iwa, was among several people who asked APHIS to preserve its current mission here. She worries that dividing the agency could lead to fewer inspectors working solely on agriculture, and costly delays for businesses waiting for their products to be cleared.

"I think Hawai'i is a really unique place compared to other states. We really need to be protected," Matsushima said.

Inspectors at Honolulu International Airport already have a difficult assignment, handling more than 6,000 foreign visitors a day, mostly tourists from Asia. They admit that it's impossible to catch everything.

Foreign visitors are expected to fill out customs declaration forms, available in English and Japanese, asking whether they are bringing in fruits, plants or meats or have been on a farm or ranch outside the United States. Visitors who claim agricultural products or whose luggage or country of origin presents a higher risk are referred to an inspection station.

On every shift, inspectors hold as many as 10 random surveys in which every piece of luggage is searched for prohibited items, which can vary from country to country. These seizures are used to measure how successful inspectors are during routine operations.

The X-ray machines used to scan some luggage are not foolproof — especially when items are buried under clothing. Apples, tangerines, pears or other products with distinctive shapes are easier to spot than noodle packets, for example.