Many of the vegetable problems facing homeowners and farmers in mid-summer are likely weather related and are considered environmental disorders, not diseases. In a normal year, the extreme heat and lack of rainfall typical of July and August can be to blame for some things and greatly affects late season growth and flowering production. However, this year has been the exception at times with too much rain. Many of the cosmetic flaws found on the fruit ready to harvest may be attributed to drastic changes in temperature and moisture levels during flowering and as well as during fruit development.
The recent heavy rainfall is to blame for tomatoes cracking and splitting on the vine – literally bursting at the seams from too much water. This environmental disorder really frustrates home gardeners because it usually affects tomatoes that are almost ripe and ready to be picked. Radial cracking radiates from the stem to the bottom and results in the most fruit damage.
Fruit cracking and splitting occurs because the fruit contents tend to absorb more water and expands at a faster rate than the fruit wall (cuticle) can withstand, causing the outer skin to split. It occurs most often during rainy periods after an extended dry period and when temperatures are relatively high. The cracked areas are then avenues for bacterial and fungal pathogens that cause fruit rots.
Radial cracking can occur at all stages of fruit growth but as fruit mature they become more susceptible, especially as color develops. Planting resistant varieties, maintaining a uniform water supply throughout the growing season with drip irrigation, mulches, or both, and maintaining good foliage cover will help reduce fruit cracks.
Another type of cracking is concentric cracking. It encircles the fruit, usually on the top near and around the stem and on the fruit's shoulders. Although it similar to radial cracking and caused by fluctuations in soil moisture as well, it typically results in minor damage and as a cosmetic flaw.
The question that then arises amongst gardeners is "can one eat cracked tomatoes"? If they are picked as soon as the cracks occur and either eaten or used then they may be safe. But as time goes by, pathogens will enter the fruit and make them bad and rot. Dr. Jean Weese, Extension Specialist for Food Safety Family and Consumer Sciences, recommends canning cracked tomatoes and eating the ones that have not split. She stresses that fresh raw foods are always a challenge as to their safety. Bacteria can get into the fruit through openings. They can even get in through the stem scar which is the place on the fruit that attached to the vine. Dr. Weese points out that even when one washes tomatoes and puts them in a tub of water, bacteria can get into the water and then into the meat of the fruit. Even pretty tomatoes that have no splits can have bacteria in them.
With cracked or damaged tomatoes, Dr. Weese advises to peel away as much of the "bad" looking surface on the tomatoes and enjoy the fresh fruit. It is far healthier than not eating fresh fruit and vegetables.
For help on other home and garden questions, call the Master Gardener Horticulture Helpline at 1-877-ALA-GROW (1-877-252-4769) or visit us online at www.aces.edu.
Shane Harris is a Regional Extension Agent for the Alabama Cooperative Extension System serving East Central Alabama.