Well, I think the more "un-crowded ' bed is, the less disease will affect the plants ,but when we get to the "dewy" time of the year ,you're gonna' get leaf-spot. I spray fungicide, which helps hold it down, but I think I'm going to go back to a "fall burn" plan, also. So, for now, I pull the spent leaves when I have the time and energy, I spray every 10 days, or so, and live with the rest! I try to practice good bed sanitation( un-crowded plants, stay out of the bed when leaves are wet, remove all the "waste' material to the trash, not the compost pile, etc., but it's still there. One trick that I think helps is to spray Miracle Grow on the plants as soon as flowering is done. This seems to cause the "old" leaves to slough off, and a rush of new leaves to start growing. You have just as many leaves to pull, but most of them are at the same time ,vs. being spread out over a 2-3 week period. Also, some cultivars are much more prone to leaf spot than others. I've found the re-bloomers to be much more resistant to both leaf spot and soft rot....Arlyn