Tomatoes with this disease cannot be salvaged and should be removed and a new plant set, Killebrew said. The best prevention is to plant the tomatoes in a silvered mulch. The light reflecting off this repels some of the disease-spreading thrips, Killebrew said. Early blight, a fungus, is the No. 1 tomato problem each year. There are no resistant varieties, so gardeners must pay close attention to spot the disease when it first appears.
Early symptoms are brown spots on the lowest parts of the plants that turn the foliage yellow.
It's very easy to spot the yellowed foliage. That's the signal to intensify your spraying program. Follow label directions and spray tomatoes with a broad spectrum fungicide each seven to 10 days after planting, even when plants appear healthy. Check with county Extension agents to confirm that the fungicide is approved for use on tomatoes. You're not going to get 100 percent disease control, but it will help you stay ahead of any problems.