Biocontrol and unanticipated consequences

An interesting story (and podcast!) in the news today:
Biocontrol agents, such as insects, are often released outside of their native ranges to control invasive plants. …As early as 1971, U.S. scientists began releasing gallflies in an effort to reduce populations of invasive [spotted knapweed]. Like all biocontrol agents, the gallflies were selected because of their [...]