UNIVERSITY PARK, Pa., Dec. 1 (UPI) -- Invasive pests moving from state to state within the United States are a greater danger than similar pests coming from outside the country, researchers say.
That's because state lines in the United States are open and for the most part unregulated, as opposed to intrastate precautions taken by other countries, a release from Penn State says.
For example, travelers in Australia moving from one state to another may encounter a quarantine stop and be required to forfeit recently purchased fruits and vegetables
"Our findings have significant implications for biosecurity policy and the need to consider security measures beyond established national borders," Matthew Thomas, a Penn State professor of entomology, said.
Invasive species cost the U.S. economy $120 billion annually.
The researchers assembled a list of the top 100 known insect pests most likely to establish in the United States.
All 100 of the exotic insect pests already exist somewhere in the country, researchers say, and in almost all cases where a pest is not found within a state, it can be found in an adjoining state or states.
In fact, 12 states had every pest they were free of existing just across their border in a neighboring state, scientists say.
"The fact that exotic species absent from one state were frequently found in a neighboring state implies the ease at which pests could arrive from a neighbor," Thomas said. "Fly into a U.S. airport from overseas and there are many biosecurity measures in place to reduce accidental introduction of a pest, weed or disease.
"Our analysis suggests the risks might be just as great flying into a domestic terminal or crossing a state boundary by car."