Exotic pests are nothing new. The hemlock wooly adelgid, which has turned woods from green to brown from the Poconos to the Great Smoky Mountains, arrived 70 years ago on a single hemlock a Virginia landowner imported for his Japanese-style garden.
But while federal agriculture officials struggle with adelgid and other established pests, emerging threats, like the citrus longhorned beetle, a wood-boring native of Asia, are presenting new headaches.
So destructive is the beetle that bans on an array of popular plants grown in Europe, including cherry trees, rhododendrons, and even cut roses from the Netherlands, are under consideration by federal officials, said Faith Campbell, a senior policy representative for the conservancy.
Europe is just one part of the $500 million international plant exporting business that has producers from Colombia to China sending more than three billion plants to the United States each year. Such foreign imports could be responsible for as much as 70 percent of the most damaging non-native insects and diseases afflicting American forests today, according to the study, which was conducted by the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara.