iris borer nematode question

OK it's time to go hunting for iris borer signs and of course there is some since I have been so hesitant to spray chemicals all over my yard... however, I would like to try nematodes to see if they can "get" the varmints before they "get" my iris.

I had a horrific experience with these nasty guys this summer eating up my iris rhizomes and turning them to mush... don't want that again. I lost 90% of my iris purchased from co-ops here in 2002 and 2003. BUMMER!

So I'm participating here again in iris coops and I want to make sure they'll be safer from the nasty little bugs that turn into ugggggly borers with big fat pinkish bodies and a ravenous appetite for my prize iris.

So I know there are 2 kinds - sf and another kind - but I don't know where to buy the ones that will get the iris borers and so I'm asking for references to places that can either sell me the right stuff or direct me to the right seller.

Thanks in advance, everyone.

Janie