University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Managing Problems When Growing Tomatoes

June 15, 2000

Tomatoes are one of the more popular vegetables for the backyard garden. Gardeners grow various types of tomatoes, ranging from a few plants in patio planters to several dozen in large garden plots. Regardless of how many or what kind, there are some common problems tomatoes may develop during the season.

There's nothing worse than going to pick that first big ripe tomato on the vine only to find the bottom half is rotten! This is due to blossom end rot, which tends to show up every summer with varying severity. Blossom end rot is due to a lack of calcium as the fruit develops, which in turn is usually due to fluctuating soil moisture as the fruit develops.

Mulching the soil and watering as needed during dry spells that may occur should keep the problem in check. Monitor the soil conditions closely through the summer when fruit is developing on the tomato plants.

Leaf diseases can also occur on tomatoes. Septoria leaf spot and early blight are two examples. Typically leaves on the lower branches are affected. Dark brown or blackish spots will appear, followed by yellowing or browning of the leaves. The disease may progress up the plant, especially during wet weather conditions.

Mulching can help reduce soil splash onto the plant, which can in turn reduce leaf diseases. Caged or staked tomatoes will have better air circulation, which may reduce disease.

Remove infected leaves as soon as they are noticed to help reduce spread. Remove infected plants at the end of the season and also practice a 3-year crop rotation. Some varieties offer tolerance of early blight.

Fungicides can also provide some protection, but need to be used weekly. Look for fungicides labeled for vegetable crops that contain chlorothalonil, copper, or maneb.

Finally, large green tomato hornworms may eat considerable amounts of foliage off tomato plants. These can be picked off by hand. Insecticides such as carbaryl (Sevin) or Bacillus thuringiensis kurstaki (Dipel, Caterpillar Attack, etc.) could also be used. Oftentimes the damage is noticed before the large caterpillar is found.


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