Some, like the ivy aphid are already in North America, but I'm not sure how much of a dent it actually makes. There's great precedent for successful introduction of biocontrol agents for other invasive species. There's also great precedent for catastrophic failures(especially in instances where there's a native close relative of a target species), so it's definitely something that needs to be very carefully explored and not to be done haphazardly.
Some, like the ivy aphid are already in North America, but I'm not sure how much of a dent it actually makes. There's great precedent for successful introduction of biocontrol agents for other invasive species. There's also great precedent for catastrophic failures(especially in instances where there's a native close relative of a target species), so it's definitely something that needs to be very carefully explored and not to be done haphazardly.