Becky, I use Bt (but not very often now that I've given up on squashes and melons etc.), soapy water solution 1/2tsp. per quart in a spray bottle, and baking soda, same recipe. The soapy water protects from aphids, whiteflies, mites etc. and the baking soda is a preventative for fungal leaf infections. (it makes the leaf surface inhospitable to spores by raising the pH value). The soap and baking soda solutions do need to be sprayed pretty often, because they rinse off in the rain, but I just keep the bottles out there and grab one or the other whenever I walk through.
The first couple of years we lived here I tried and tried to grow my favorites, Brandywine tomatoes. They were so easy and successful in Utah where we lived before, but I hardly got any fruit from them here before some wilt, disease or fungus would take them out. One day the plant would be looking pretty good, the next I'd come out and it would be standing there with all the leaves hanging down.
Another Master Gardener clued me in to the disease resistance that is bred into the newer hybrids. Suddenly I was harvesting lots of great tomatoes again. You can say what you like about heirlooms tasting good, I really don't think they're all that much better than some of the hybrids I've grown, and the hybrids survive and bear a nice harvest, too. I even have one, and started the last of its seeds just last week, that is supposed to be resistant to blights. It's called 'Ledgend'.
