The tomato plant disease known as late blight occurs during periods of cool, rainy weather that may come at the end of a growing season. It looks almost like frost damage on leaves, causing irregular green-black splotches. Fruits may have large, irregular-shaped brown blotches that quickly become rotten. This tomato plant disease fungus also affects potatoes and can be transferred from them. Use the same controls as for septoria leaf spot.
Mosaic virus attacks many kinds of plants and is common in tomatoes. While mosaic virus doesn’t kill the plant, it diminishes the number and quality of fruits. Blossom drop is another. It’s a disease that is brought on by extreme temperatures. Blossom drop occurs when temperatures rise above 85°F or drop below 58°F. Often, you won’t notice that there was any damage until you have fewer tomatoes to harvest at the end of the season. Prevent blossom drop by using row covers to raise night temperatures.
Listen to Cathy Isom’s report below.