Introduced plants, such as the English ivy 

 pictured here, can invade thousands of acres of 

 forest before they are recognized as threats to 

 native vegetation and w/7d//fe. 



manent alteration of biological communities. 

 Although much attention is directed at intro- 

 duced insects and diseases, the current and 

 potential effect of introduced plant species on 

 forests is huge. Not only do exotic plemts com- 

 pete with native vegetation but they can also 

 change the physical and biological environ- 

 ment. Changes have been noted in moisture 

 and nutrient status, microbial populations, 

 and soil characteristics where exotic plants 

 have become established. Organisms depen- 

 dent on native plants and adapted to a par- 

 ticular environment are also affected. 



Introduction of Exotic Pests 



Exotic pests usually travel to new areas as 

 hitchhikers. Weed seeds, fungus spores, insect 

 eggs, cocoons, or larvae arrive on plants, fur- 



Radiata pine wood chips in a Chilean ship hold. 

 Regulations require inspection and sampling. 

 Chemical or heat treatments are used to destroy 

 pests associated with chips. 



niture, lawn mowers, logs, ships, cars, trail- 

 ers, trains, and planes. Less frequently, they 

 are blown or washed in by storms or other 

 anomalous weather. Port-Orford-cedar root 

 disease is thought to have arrived in the Pa- 

 cific Northwest on infected ornamental plants 

 in the 1920s; it then spread to both native Port- 

 Orford-cedar in southwest Oregon and orna- 

 mental Port-Orford-cedar throughout western 

 Washington and Oregon. 



Increased travel, population expansion, and 

 new trade with South America, Japan, China, 

 and the former Soviet Union will contribute to 

 increased introductions of plants and animals 

 and increased chances that they will become 

 established once they arrive. The benefits of 

 economic growth for states such as Oregon and 

 Washington resulting from trade with other 

 countries has to be weighed against the risk 

 of introducing new pests and the potential 

 damage to forests. New regulations for imports 

 of logs and lumber (and other unmanufactured 

 wood items) have recently been implemented 

 by the states and the Animal and Plant Health 

 Inspection Service (APHIS), a branch of the U.S. 

 Department of Agriculture, to reduce the risk 

 of introducing forest pests into the United 

 States. 



Overview — 1 8 



