Invasive species can quickly become ecological and economical disasters. The emerald ash borer beetle has killed over 30 million ash trees since it was detected in North America in 2002. European gypsy moths defoliate millions of acres of forest every year from North Carolina to Wisconsin to Maine.
Beckham [Alishia Beckham, a Customs and Border Protection agricultural specialist] carries a backpack full of tools: cards illustrating the moth’s life stages, binoculars to inspect areas of the ship she can’t reach, a paint scraper to pry off egg masses, and a plastic container with a dead adult male and an egg mass to show crew members what she’s looking for. Most crews are very cooperative and want to know what to look for, Beckham says.
The Asian gypsy moth, like its European cousin, is a rapacious leaf-eater, but it feeds on a wider variety of trees. Unlike the flightless European female, the Asian female can fly up to 25 miles before laying its eggs, meaning it could quickly spread across the country.
In early August, Beckham stepped aboard a ship in Seattle and found more than 100 Asian gypsy moth egg masses, each containing up to 1,000 eggs.
She ordered the ship immediately escorted out of U.S. territorial water by the Coast Guard before the eggs started hatching.
After hatching, the gypsy mother caterpillars let out a silken thread to catch the wind—a mode of travel called “ballooning” that can carrying them up to five miles.
“Once the larvae start ballooning, we’re in trouble,” said Eric Johnson, the Customs Service’s agriculture chief for the Seattle area. He estimates if gypsy moths hatched at a Washington port, they could infest the forests of the Cascade Range—about 30 miles away—within five years.
The federal government spends over $1.3 billion every year to detect, eradicate and control invasive species, according to the Department of the Interior.
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.
Even groceries for crews of incoming vessels can harbor pests, such as fruit flies, and they come from multiple sources, 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, U.S. melons, apples from New Zealand, Spanish beef and Dutch poultry.
Once inside the U.S., invasive species can spread by riding on firewood, cars, plants, motor boats, even on mud-caked shoes.