These are one of the most despicable creatures I have encountered in a long time. They are right up with ticks - at least chickens like ticks but nothing I know of eats these little buggers.
I'm working hard to keep them from destroying my flowers/herbs/and trees. I finally think I have a good combo - garlic and cayenne pepper with a tablespoon (I think I put than that in my sprayer), fill with water and spray. This is a daily thing for me because I forgot to spray my yard in the spring.
I did that last year and they were non existent - this year, with all the water they can burrow deeper and come out strong - blech!
So if you're looking to salvage your gardens, try using garlic and cayenne with some dish soap. Let me know if it works for you. If you got a tried and true recipe that is clean, send it along and I'll pass on the info!