I have a patio planter that I plant tomatoes and peppers in every year. And, as one might expect, every year the same diseases pop up. The peppers always do fine but the tomatoes usually fall victim to a fungal leaf spot disease, which I assume is Septoria since it shows the classic pattern: lower leaves turning yellow and getting brown/gray spots, then eventually dying, while the upper leaves are unaffected. This year, I thought I'd eliminated the disease. I dumped all the soil out, washed the planter thoroughly with detergent, let it dry, put in new soil, and then planted the tomatoes. And yet, I'm still seeing the disease this year. Either I didn't do a good enough job, it was introduced from the tomato cage I didn't think to wash, or I had the bad luck to purchase an already-infected plant. Since I spotted the disease this year (pun intended), I have sprayed it regularly with chlorothalonil, a potent antifungal that's supposed to work on Septoria. Yet the disease continues to progress rapidly. I don't know if the strain is immune, the jug of chlorothalonil has gone bad (the date stamp is 07062801...interpret that how you will), or something else is going on. Suggestions?