The Q&A Archives: Controlling Tomato Fungus

Question: For the past several years my tomato plants have been infected with the fungus where the leaves at the bottom of the plant get black spots, turn yellow, and eventually die. This moves up the whole plant until it eventually dies. I can usually slow the spread of this disease by removing the infected leaves/plant, but eventually it spreads to all the plants and the whole patch eventually dies. (Some ripe fruits also get brownish spots at the top where they meet the stem). Because I live in Northwestern Wisconsin, our growing season is rather short. I have raised beds and cover them with clear plastic in spring and fall. What is this disease? I don't like to spray harsh chemicals on my garden, so is there anything else I can do to prevent it or get rid of it? And finally, can you suggest any type of tomato plant that is resistant to the disease in my area? Lisa Magnuson Hudson, WI

Answer: It sounds like Early blight fungus to me. The fungus is in the soil and as soon as the rains comes and splash soil onto the leaves in summer, the fungus starts attacking. First the lower leaves, then it moves up the plant. Eventually it can kill all the leaves. The best precaution is to mulch your plants early in the season, keep them healthy with regular watering and fertilizer, pick off thr lower leaves as they get infected and discard them, and if you're really in a crisis, spray the leaves with copper sulfate early in the season.

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