Paul I used to think the same when I had plants with Leaf Spot and Rust but after visiting most of the major gardens I realized it must not be that big of a deal in the health of the plant just about every major grower I seen had it everywhere and the largest of them all Schreiner's had it the worst the two that had none what so ever (Superstition and Napa) have a pretty intense spraying program and you could definitely see great results from it but they both don't get anywhere near the rainfall that Oregon gets and I think for most growers on a commercial level it is about impossible to get rid of it. How do you treat 200 acres on a weekly basis and still pay the light bill ? I could be wrong and maybe they do treat there fields for it but
Who Knows, I really struggled with it this year at home in mine I was doing well until just after bloom season and then we had a couple rainy weeks and it seemed to explode. I sprayed mine all spring with a fungicide and sticker up until bloom but I am beginning to think it is more of a soil based fungus than something that is in just a particular plant, I have not given up trying to get rid of it all together but it certainly is a tough nut to crack.
