Kate, glad you continued to figure out what these were, I don't know that I would have done that!! So good on you!
I think you could do more reading and figure if there is a plant which repels them and plant the bed for a season with that (like onions or garlic or mint??) then in Sept you could do the micro worm thing! (It seems like a lot, but I think being one summer out of he bed, then planting it "correctly" with no more loss of plants would be a good thing!)
Do keep us posted and stay motivated!!!
Cheers