Gypsy-moth watch at Port of Seattle

Alisha Beckham uses a hand mirror and a flashlight to defend the United States from foreign invaders.

Working aboard ships three football fields long that arrive stacked with truck-sized cargo containers in Seattle's bustling port, the U.S. Customs and Border Protection agricultural specialist scours for bugs, plants or pathogens that could lay waste to native species.

She checks around door frames, pipes, lifeboat winches and other nooks where an Asian gypsy moth might have laid its eggs.

Invasive species can quickly become ecological and economical disasters. The emerald ash borer beetle has killed more than 30 million ash trees since it was detected in North America in 2002. European gypsy moths defoliate millions of forested acres every year from North Carolina to Wisconsin to Maine.

"There are so many places on a ship, it could literally take all day if you inspected every inch of the ship," Beckham said. "We do what we can."

Beckham carries cards illustrating the moth's life stages, binoculars, a paint scraper to pry off any egg masses, and a container with a dead adult male and an egg mass to show crew members what she's looking for.

Leaf-eating menace

The Asian gypsy moth, like its European cousin, is a rapacious leaf eater, but it eats a wider variety of trees. Unlike the flightless European female, the Asian female can fly up to 25 miles before laying its eggs, which means it could quickly spread across the country.

In early August, Beckham stepped aboard a ship in Seattle plastered with more than 100 Asian gypsy moth egg masses, each containing up to 1,000 eggs.

Beckham ordered the ship escorted out of U.S. territorial waters.

"If there are a hundred egg masses and they start hatching, we can't send the ship through Puget Sound because there are so many islands the caterpillars could land on," she said.

After hatching, the caterpillars let out a silken thread that the wind catches — this is called "ballooning." They can travel up to five miles, depending on conditions.

"Once the larvae start ballooning, we're in trouble," said Customs and Border Protection Chief Eric Johnson. He estimates if they hatched at a Washington port, they could infest the forest of the Cascade Mountains within five years.

The federal government spends more than $1.3 billion every year on detecting, eradicating and controlling invasive species, according to the Department of the Interior.

Very few nonnative species become invasive, but a single species can cause millions of dollars in destruction. Zebra mussels annually cause more than $5 million in damage in the Great Lakes. Cornell University researchers estimated in 2004 that invasive species cost the U.S. economy almost $120 billion each year.

The rise in international trade has increased the opportunities for invasive species to hitchhike into the U.S.

"A continued influx of invasive species is going to be in our future," said Jim Marra, an entomologist for Washington state's Department of Agriculture.

A worldwide issue

Russia and Japan also monitor for Asian gypsy moths and share the information with U.S. officials, who use it to identify high-risk ports. The moth was detected this year at a port in China, which does not collect or share such information yet, according to Johnson.

Infestations can prompt bans on a country's exports.

"It might be in the best interest of a foreign country to not disclose that a major, major port is infested," said Beckham, adding, "But we've had very good relationships with foreign countries, from my experience. But who's to say?"

The myriad international and regional regulations covering invasive species and trade are imperfect. One of Beckham's colleagues found an Asian long-horned beetle larva burrowed into a wood shipping pallet. The wood was stamped with the seal of the International Plant Protection Convention, meaning it should have been heat-treated, which would have prevented the larva from getting into the wood.

Even an incoming vessel's food can harbor pests such as fruit flies, said Beckham. A ship's food is often a testament to its worldwide voyages. Inspecting one ship recently, she found zucchini from Hong Kong, lemons from Argentina, melon from the U.S., apples from New Zealand, Spanish beef and Dutch poultry.

To protect its agriculture industry, California requires ships to lock up food from certain countries while in port, said Beckham.

Outside San Francisco, state and federal officials are fighting the light-brown apple moth. It has caused up to 20 percent crop losses in New Zealand, said John Sacks, a spokesman for the U.S. Department of Agriculture's Plant Protection and Quarantine division. For California, that could mean losses between $680 million to $2.7 billion if the moth becomes established.

Beyond points of entry, programs of detection, eradication and control keep invasive species in check. Tools range from pesticide sprays to breeding sterile male insects.

Once in the U.S., invasive species can move around on such things as firewood, cars, plants, motorboats, even on mud-caked shoes.