Lymantria dispar(Gypsy Moth)
Caterpillar
Photo by Tim Mack

There are many ways in which an invasive species can enter the United States. A majority of the most likely pathways involve humans.

Many imported goods are packed in wood containers. The wood may contain insects and plant diseases harmful to trees in the U.S. This is probably the way that the Asian Long-horned Beetle (ALB) entered the U.S.

After crossing an ocean and nearing a U.S. port, ships may release ballast water that has been carried to keep the ship at the maximum performance and safety level. A large ship may release millions of gallons of water along with species of plant and animal life not native to that port.

Some people smuggle items prohibited by U.S. laws and regulations. Smuggling of fruit has caused many outbreaks of the Mediterranean Fruit Fly (medfly). A single outbreak of medfly may cost the U.S. taxpayers millions of dollars to eradicate.

Some invasive species enter as a contaminant with a legally imported item. This may be how Giant Salvinia entered the U.S.