Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Scientific American FRONTIERS Logo
TV Schedule
Alan Alda
For Educators

Future Shows
Special Features

ALien Invasion

  The Silken Tree Eaters
Photo of longhorned beetle
  Cutting, chipping and burning infected trees is the current solution to the longhorned beetle threat.

Alien species often arrive in the environments they come to terrorize purely by accident. Ballast water taken into a ship's hull for stabilization can be innocently released into a harbor halfway around the world. But that water could contain traces of life ready to multiply out of control in the foreign port.

One such accidental tourist was the Asian longhorned beetle. It first arrived in the U.S. in the 1980's in wooden packing materials from China. Soon these voracious eaters were infesting maple trees, laying their eggs inside the trunks and letting the larvae literally eat their way out. The beetle problem is confined to the New York and Chicago areas. That is, for now.

Other alien species have had a little more direct help from man in getting a foothold in a new area. In the 1870's, Etienne Trouvelot from Medford, Massachusetts imported the European gypsy moth in the hopes of sparking a silk industry in the U.S. But soon the moth had escaped, and the forests of the Northeast would never be the same.
Photo of gypsy moth caterpiller  
A gypsy moth caterpillar dines on oak tree leaves.  

Dining on the leaves of the region's abundant oak trees, the moth population exploded, taking over some 40,00 square miles of forest by the late 1920's. Today, the invasion has progressed as far west as Wisconsin. USDA scientist Vic Mastro has taken up the gypsy moth fight that began over one hundred years ago. Accepting that the moth is here to stay, he and his team are now devising ways to help control its spread. As Mastro says, the single best way to fight an alien species is to prevent its introduction in the first place - a task which is becoming harder and harder to accomplish.

For more on this topic, see the web feature:
America's Least Wanted
Dr. Killer Bee


return to show page

Photo: USGS





The Silence of the Birds Green Invader The Silken Tree Eaters Dust Busting Resources Teaching guide Science hotline video trailer Contact Search Homepage