I've been using the same thing with so-so results. I don't get out to my girls enough to know exactly WHAT is eating them, so it's hard to say. Seems like it's helped, though. Right now they're all dying from heat stress, so I dunno if it matters anymore. One thing that HAS helped, and I don't know how you could go about implementing this yourself, is that this little fella took up residence on one of them:
turns out it's a green lynx spider. it eats all kinds of things that eat plants and has long been used as a natural pesticide in this region: http://en.wikipedia.org/wiki/Green_lynx_spider