Troubleshooting Tomatoes

It's midsummer and the tomatoes are ripening. If your luscious fruits aren't forming correctly or your tomato bush is struggling, check out these possible reasons for your tomato's downfall. You still have time to save your crop.

Fruit Problems

There's nothing more frustrating than having tomato fruits set and start growing, only to see them develop cracks or catface, or rot on the vine. Fruit cracking is usually caused by fluctuating soil moisture conditions. A dry period followed by a heavy downpour stimulates the fruits to grow too quickly, causing the fruit to crack. This most often occurs on cherry tomatoes and older varieties. Keep the soil mulched and well watered to avoid moisture extremes.

Blossom end rot also is caused by fluctuating soil moisture conditions. In this case, the blossom end of ripening fruit rots before maturing. Fluctuating moisture causes a temporary calcium deficiency in the fruit. Calcium is transported by water and is critical to keeping cell walls strong. Again, mulching and regular watering will alleviate this condition.

Catfacing is a condition where cracks develop around the top of the fruit. It is mostly variety specific, so try modern varieties such as 'Carnival' that resist catfacing.

Leaf Problems

Tomato plants are susceptible to a number of foliar diseases. The symptoms of these diseases, such as early blight, septoria leaf spot, and bacterial speck, look similar. Often the disease starts as yellowing or brown spots on the leaves. The disease spreads, killing the leaves, and it may even attack the fruit. Other diseases, such as Verticillium wilt and virus, attack the whole plant at once, causing it to wilt and die when young. The key to controlling any tomato disease is prevention.

Rotate your crops each year to avoid soil-borne diseases. Some serious diseases can live in the soil for several years. Try to wait three years before planting tomatoes where they grew before. Also, avoid planting them where potatoes, eggplants, or peppers grew the previous season, because some diseases attack all these vegetables and live in the soil from year to year.

Plant resistant varieties, such as 'Big Beef' and 'Better Boy', that are resistant to Verticillium and Fusarium wilts. Most seed companies list resistance to these diseases by putting F (Fusarium) or V (Verticillium) after the variety name. N stands for resistance to nematodes, the tiny worms that plague many southern gardens, causing stunting of the plants and poor crops. Click here for more disease-resistant tomato varieties.

Clean up the garden at the end of the season. Many disease-causing organisms spend the winter in plant debris in the soil. Destroy any obviously infected plant material rather than composting it.

Critter Problems

Insect pests, such as tomato hornworms (see below) and white flies, can be a problem on tomatoes. Sometimes, however, the critter eating your fruit has wings or four legs. During dry periods squirrels and birds have been known to munch on ripening fruits. They aren't interested in the flavor as much as the water inside the fruit. Consider setting up a birdbath and covering your plants with a floating row cover to discourage them.

For more on growing tomatoes, go to the Virtual Vegetable Guide.

Question of the Week

Q. I found several large caterpillars with tails munching on my tomatoes. What should I do to get rid of them?

A. It sounds like you're seeing tomato hornworms, which can grow to an alarming size! Like most caterpillars, hornworms can be controlled by using Bt (Bacillus thuringiensis). However, since tomato hornworms can do a lot of damage in a short time, you may want to remove the ones you see by hand. If you see a caterpillar with what looks like grains of rice all over it, relocate it elsewhere in the garden rather than killing it. It has been parasitized by a braconid wasp, and the "rice" are actually the wasp eggs. The emerging larvae will feed on the hornworm. These small wasps are harmless to humans, but will help keep the hornworm population in check.

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