Curious problems can arise with tomato plants
As tomatoes ripen, curious problems often show up on the fruit. These range from uneven ripening to zippering, catfacing and growth cracks.
Uneven ripening appears as yellow or green areas remaining while the majority of the fruit turns red. This can be due to too low of temperatures or compacted soils that are too wet and restrict root growth. Uniform watering and the use of mulch can help reduce this issue.
Zippering is a narrow, corky brown line that forms across the fruit. It usually occurs when the flower anther sticks to the developing fruit. As the fruit expands, a scar develops from the bottom up towards the stem. Some varieties are more susceptible than others.
Catfacing describes a fruit that becomes deformed on the bottom. The fruit is deformed but does not turn brown or black as it does with blossom end rot. Catfacing can be due to colder than normal temperatures during flowering.
High nitrogen fertilization, incorrect pruning and exposure to herbicides may also lead to deformed tomatoes. Fruit is usually still edible with zippering or catfacing.
Growth cracks form when the flesh within the fruit grows faster than the outer skin. These cracks can be concentric rings around the stem end, or radial cracks down the sides. Cracks most often form because of over-fertilization with nitrogen or extreme fluctuations in temperature or moisture.
Sunscald appears as white or yellowish blisters on areas exposed to sunlight. Over time, the exposed area turns tan and feels papery. It is seen on green fruits first and can lead to fruit rots. Anything, such as a leaf disease, that reduces the amount of foliage so the fruit is more exposed to sunlight can lead to sunscald.
While there are a number of diseases and insects that can also affect tomato fruits as they develop, the above are the most common abiotic (not a disease or insect) issues seen on tomatoes.
When any issue develops, it is important to positively identify the true cause of the problem prior to applying any type of fungicide or insecticide.
To reduce abiotic problems, it is most important to provide the best growing conditions possible. This includes a well-drained soil, even watering, even fertilization, correct plant spacing, and the use of mulch. Avoid excessive irrigation and nitrogen fertilizer; and also select the right tomato varieties.
Along with what caused the issue, gardeners often ask if the tomato is still safe to eat. In most cases, the affected part can simply be cut out and the tomato eaten. Sometimes a large enough portion of the fruit is affected resulting in poor eating quality.
Source: Missouri Botanical Garden Tomato Fruit Problems
Kelly Feehan is an extension educator for Nebraska Extension.