ASIAN INVASION: The Asian gypsy moth larva poses a threat to the U.S.
Photo courtesy USDA

In a major step toward controlling the spread of tree-destroying gypsy moths, China has agreed to allow scientists to inspect forests near shipping ports to gauge the risk of the pests there hitching rides on ships to the U.S.

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In exchange, the U.S. agreed to share its expertise on exterminating other invasive bugs, such as fire ants. Officials at the U.S. Department of Agriculture (USDA) say the move could help prevent the international transport of a faster-spreading and particularly destructive Asian gypsy moth variety.

The deal with China is the fourth the U.S. has cut in an attempt to get a handle on the problem; it has more extensive agreements with Russia, Japan, and South Korea. Mike Simon, an offshore pest mitigation expert with the USDA's Animal and Plant Health Inspection Service (APHIS), says scientists in China are set to begin trapping and studying gypsy moths this month.

The North American gypsy moth is blamed for defoliating trees in national forests and residential areas in at least 20 states as well as across southeastern Canada. U.S. Forest Service officials say that aerial pesticide spraying of hundreds of thousands of acres each summer has slowed but not stopped the moths. They add that they are trying to keep a lid on the native population as well as prevent the more virulent Asian variety from reaching U.S. soil.

The Asian moth made two minor incursions into U.S. ports during the 1990s, but both times were quickly eradicated. Over the past year, inspectors have again found Asian egg masses on foreign ships arriving in U.S. ports. U.S. Customs and Border Patrol agents are authorized by law to bar entry to foreign vessels carrying invasive bugs or their eggs and to order them offshore to be scrubbed of the pests before unloading cargo. But Simon says it would be more effective to verify that no eggs, caterpillars or adult moths are aboard ships before they set sail from overseas ports.

The main concern: that the virulent strain of Asian gypsy moth, if introduced to the U.S., could exacerbate damage to North American forests.

"The west coast states are basically terrified; it would be devastating to their timber resources, both for industry and recreation," Simon says. That's because, other than a few isolated and quickly squashed outbreaks, the U.S. west coast is generally free of gypsy moths. Without competition from local populations, any Asians that arrived there could thrive.

At least 10,000 cargo containers and 100 ships arrive daily in the Port of Los Angeles, most of them from Asia, which poses a real risk, he adds.

The North American strain, Lymantria dispar, now stretches from Canada into North Carolina, Minnesota and Wisconsin, with pockets of infestation beyond its contiguous range. It is currently expanding its  reach by about five miles (eight kilometers) a year, according to ecologist Patrick Tobin, head of the technical advisory committee* for the U.S. Forest Service's Slow the Spread, a program to manage the gypsy moth.

As its name suggests, the program, which was first funded by Congress in 2000, is trying to decelerate the expansion of the gypsy moth's range. It monitors 10 states along the region's leading edge for outbreaks and decides which ones to combat with insecticides. It also educates truckers, plant nurseries, the timber industry, motorists and recreational forest users about ways to avoid transporting the pest. Human movement helps the gypsy moth move faster than it does on its own.