Well, the early blight has hit some of my tomato plants. I have four groupings of plants scattered out in a wide area, so I won't lose all of them, but I'm going to probably lose my best producers. I'll share with you my research (and my shame) so that it might help some others.
Early Blight is a fungus. The spores can travel on the wind, come from purchased seeds or transplants, or be present in the soil. Once the spores are in your soil, then you'll face the blight every year that you grow tomatoes in that same spot. Crop rotation helps but is no complete cure.
Affected leaves turn yellow with ringed spots and then die. The stems turn yellow, and it generally goes from the bottom of the plant upwards. Where the leaves touch dirt they come into contact with the spores, usually when watering and this is yet another method of disease transmission. Eventually you'll lose the whole plant and it will spread to other nearby plants.
Here's a handful of things I did wrong that helped cause/propagate the damage:
1. I put indeterminate plants in cages. They get bunched up too tight and it reduces the airflow and sunlight to the center and base of the plants, creating a perfect environment (dark and moist) for fungus to thrive.
2. I watered over the top of the plants instead of the base. This allowed water to drip down inside the plant and caused drooping leaves to come into contact with the soil. One should always water early in the morning so that the sun can dry out the plants thoroughly as quickly as possible, and always apply water only to the base of the plants so it soaks into the soil instead of laying on top of the leaves.
3. I didn't remove the infected leaves and branches as soon as I saw this. In my defense, I didn't know what was wrong, but by the time I figured it out I'd already lost one plant and it had spread to all the other neighboring ones. Removing the infected area helps increase air flow to the center of the plant and reduces the number of spores. It can slow the spread, but perhaps not stop it completely.
4. I did not wash my tools and hands as I moved from plant to plant picking ripe fruit and pruning suckers. The spores were carried on my hands from plant to plant and area to area. (I've got to quickly act to save the other isolated areas where I had tomato plants now.) Again, early disease identification is crucial. If you don't know you're infected, you'll do everything else wrong as well.
5. My plants are too close together. I planted the transplants two foot apart thinking since they'd be caged it wouldn't be an issue. These were in some raised beds where space is critical and I was trying to maximize it. A poor decision overall. The close proximity helped the fungus to spread.
So now I'm playing catch-up with a permanent affliction in my garden area. I'm removing all dead/infected foliage and putting a heavy mulch underneath the survivors. I'm burning the pruned foliage instead of putting it into the compost. The ash will go into the compost, but I don't trust that my pile will heat up enough to kill the spores. I'm also applying a heavy dose of copper hydroxide (an organic-approved fungicide) to all the remaining plants and the contaminated soil.
I hope this helps. I have 68 tomato plants in the ground (5 varieties) and I'm going to lose 4 of them for certain and up to 12. Worse, those were the ones in the raised beds which I have designed to be covered with plastic in order to extend the growing season, so if I lose everything there then I'll have no tomato plants surviving past the first frost. The total investment in the transplants is only about $12, but the lost income is estimated to be $80+. An expensive lesson to learn, but one that I figured I should share.
