Spider mites!

Hi all,

I've been a lurker for a long time but have just recently started commenting on DU.

This summer has been awful for my little container garden. All of my tomatillos got destroyed by what looks to be spider mites, and it looks like they've started attacking what's left of my tomato plant. Frost will take care of the little buggers soon enough (I'm in zone 4), but I'm wondering if anyone here has an organic solution for them in case they come back next summer? Any idea what could have attracted them this year vs. in the past? The only real change to my garden this year was the addition of lots of compost to my usual potting mix.

Thanks and look forward to becoming a more active DUer!