Answer: The two most devastating problems attacking tomato plants are early blight and late blight. Early blight is caused by the fungus Alternaria. It begins with small spots on the lower leaves and progresses to the stems. The spots sometimes take on a bulls-eye appearance. Regular use of the fungicide lime-sulfur (Bordeaux) will help protect your plants. Late blight is caused by the fungus Phythopthora, and cool, wet conditions favor the development of this disease. The affected plants respond to regular fungicides sprays that include copper. Be sure to plant your tomatoes in a different spot in the garden this year to avoid any soil-borne pathogens from last year. Always remove and destroy any affected plant parts. And, if you use fungicides, always read and follow the label directions.
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