Some sawflies only have one generation a year so once they're gone they won't be back that same year. So it depends if this particular one has more than one generation, that's where a more precise ID would be useful. The links I gave above suggest it only has one generation, though, in which case once gone for this year it won't be back. You could just keep an eye on the plant to make sure. There are several insecticides labeled for sawflies, you could ask at your local supplier what they recommend and have available for them in your area. Diatomaceous earth can also be used for sawflies but whether that's practical or not would depend on the size of the plant and whether you mind its looking dusty temporarily.
