Susan - your zone would make a difference for sure. For the most part, blue hostas will usually do quite well in my zone unless we have an unusually hot summer and even then, not all will be badly affected.
Gerry - I've been told that the AHS Journal about to come out features article on foliar nematodes. But once they are in the garden, you pretty well have to live with them - at least we do because anything that will be really effective in treating them is impossible to buy in Ontario. For hostas, it means that late in the summer, the plants don't look very nice. Early on, it's near impossible to tell what might be affected; so I no longer share many hostas. And the nematodes affect a wide range of perennials, not just hostas. As a result, I will no longer buy from plant sales either. No point in treating individual hosta if I plan to put them back in the garden.
