Analysis of historical insect invasions in the United States resulting from plant imports demonstrates the beneficial impacts of government programs to exclude plant pests. However, it also reveals that over one-quarter of insect species invading the nation remains undiscovered and may manifest impacts on agriculture and forestry in the future.

Over the past two centuries, thousands of insect species have moved between world regions accidentally with imported live plants, often causing considerable damage to agriculture and forest trees. Unfortunately, most of these invasions are not discovered until decades after their establishment, and this temporal lag obscures the relationship between plant imports and insect invasions. A Northern Research Station scientist and his team applied a novel modeling approach to historical records of insect invasions and live plant imports to the United States to reconstruct historical introduction rates and predict future numbers of invasions. Findings indicate that efforts to reduce biological hitchhiking on live plant imports, often referred to as “biosecurity,” are working. However, more than a century of insect invasions also suggests that increased trade may offset the effects of improved biosecurity. Further, as many as 25 percent of established nonnative insects may have yet to be detected in the nation’s forests and agricultural fields. Results highlight the value of continued efforts to discover and prevent damaging insect invasions in the United States.