Tomatoes are the most popular vegetable to grow in Mississippi in both home gardens and commercial production. Not surprisingly, many questions arise from gardeners and commercial growers about various problems that occur during the season.
This publication discusses some of the most common disorders, methods of prevention, and sources of more information. Hopefully you will see very few, if any, of these situations in your own tomato plants this year.
Misshapen Fruit
Misshapen fruit are common in home gardens. There are several factors that cause misshapen fruit, but the most likely is low temperature.
Tomato fruit will develop the best shape if the temperature is above the mid-60s (°F). Lower temperatures cause ridged fruit (a bumpy shoulder) and catfacing (ugly bottom of fruit; see below). Planting a little later, when temperatures are higher, will avoid some of these problems.
Some varieties are more prone to produce misshapen fruit. Fruit of the larger beefsteak types as well as many of the older heirloom varieties are commonly misshapen.
Blossom-End Rot
Blossom-end rot (BER) is probably the most common problem across all types of production (home garden, field, and greenhouse). It appears as a dry, leathery (not mushy), dark brown or black area, usually at or near the bottom of the fruit. BER can sometimes occur on the side of fruit, and occasionally only on the inside, so the BER is hidden until the tomato is sliced open. Sometimes the spot is sunken, and these tomatoes often ripen before all others.
BER is not caused by an infectious agent (pathogen) and is, therefore, not a disease. It is a physiological disorder caused by lack of adequate calcium in developing fruit. Most Mississippi soils have enough calcium for tomato fruits to develop properly, but it is a good idea to have the soil tested to make sure.
A tissue analysis during the season can also help to identify nutritional deficiencies and help ensure that plants are absorbing needed nutrients for proper growth and development. Submit soil and tissue samples to the MSU Extension Soil Testing Lab () for analysis. Visit the lab website for the most up-to-date fees and submission forms. Instructions on how to collect and submit soil and tissue samples are available in MSU Extension publications IS346 Soil Testing for the Farmer, IS1294 Soil Testing for the Homeowner, and P1224 Plant Analysis Sampling Instructions.
It’s common to see BER on the first tomatoes of the season. While low calcium in fruit is the cause, the real culprit is often drought. Without a steady supply of water, the tiny root hairs dry out, which limits the amount of calcium the plants can absorb and supply to developing fruit. Don’t let plants wilt between waterings. The best way to prevent damage to root hairs caused by drying out is to provide consistent water and to mulch around plants.
BER can be especially problematic to tomatoes grown in containers because they have a tendency to dry out more easily. Be sure to provide mulch around the tomatoes to protect the roots. Some varieties are more susceptible to BER than others. If the problem continues, try planting a different variety the following season.
It is important to note that while BER is not a disease, fungi are often observed on damaged tissue as secondary infections. These fungi are commonly opportunistic fungi and not pathogens that cause common tomato diseases. Additionally, BER is sometimes confused with the disease buckeye rot, in which brown, circular lesions develop on fruit. In contrast to lesions associated with BER, buckeye rot lesions often appear oily and have concentric rings. Fruits that develop buckeye rot are often located close to the ground. For additional information on buckeye rot, see Publication 3175 Common Diseases of Tomatoes.
