Question: My tomatoes have deep brown indentations on their tops, as well as some large and some very small yellow spots. Some of my plants turned brown and died back, producing only one or two small tomatoes. What went wrong?
Answer: The brown spots are most likely caused by a fungus called alternaria. Next year, look for plants that are resistant to this fungus. If you spray your tomatoes, use a spray without lime, such as maneb, zineb, captan, or chlorothalonil (ask your local garden center where to obtain these). You also might be applying too much manure or overwatering your plants.
The yellow blotches are probably tomato spotted wilt, a virus that affects the leaves of the plants as well and is extremely difficult to control. The only way to get rid of this is to remove the diseased plants.
You may want to check with your local Cooperative Extension Service office to find out which types of tomatoes are best suited for your growing area.