The foreign insect pests that invade our nation’s forests may be small, and most of them get little attention.

But when they are bad, they are very, very bad, and we all pay the price. Trees are lost, forests are disrupted and millions of dollars are spent to deal with the problem.

According to a comprehensive study published in the December issue of BioScience, without better efforts to stop the transport of exotic forest insects into the United States and to control the devastating species that are already here, our forests, woodlands and urban trees are at serious risk, with economic losses projected to range in the billions of dollars.

Deborah McCullough, Michigan State University (MSU) professor of forest entomology, was involved in the study that included researchers from the University of California at Santa Barbara, the University of Central Florida (UCF) and the United States Department of Agriculture (USDA) Forest Service. They identified the number of non-native forest insect species that became established in the U.S. between 1860 and 2006. The scientists also looked at the extent and type of damage caused by different groups of pests. They also examined whether the kinds of pests coming into the country had changed over time. The comprehensive information compiled by the researchers should help state and federal regulators to strengthen regulations designed to exclude potentially damaging pests from entering the U.S. and to develop better methods to detect and manage the exotic forest insects that are already here.

“We found that more than 455 non-native species of tree-feeding insects and at least 16 pathogens that affect trees are now established in the continental United States,” McCullough says. “This isn’t a new thing – exotic forest pests go back to the 1800s, and at least one of them was here before 1700.”

McCullough notes that only about 14 percent of the 455 insect pests cause substantial economic or ecological damage.

“That may not seem like much, but it’s still pretty scary,” she says. “Some of these pests can be devastating when they become established in a new habitat.”

In past decades, most of the invasive forest insects in the U.S. were from Europe. Increases in global trade and travel, however, have provided more opportunities for forest insects from Asia and other world regions to enter the U.S.