Thanks to "Mother Nature" in 2012, many gardeners and commercial growers have been battling abiotic problems of tomatoes! Many have been taking notes and comparing problems on tomato cultivars that are more susceptible to abiotic conditions on fruit such as Yellow Shoulder, Sunscald, Rain Check, and Fruit Cracks. Other abiotic problems on tomato fruit are Blossom end rot, Catface, Spider Track, Puffiness, and Internal White Tissue.
The pictures below have symptoms that are suspected to be Rain Check.
Rain check is the many, tiny concentric cracks that form on the shoulder of the fruit. Damage will be most visible on the exposed, mature green, and possibly breaker fruit after rains; but unexposed fruit or small, immature green fruit sometimes be affected as well. This problem is mostly observed on large, fresh-market tomatoes, rather than on smaller fruited cultivars. If conditions are right, black shoulder can occur (as seen in the pictures below.)
The cause of rain check is not known. The rain might alter the fruit temperature or water uptake. This, in turn, may hinder the development of the shoulder epidermis. Another theory is that the rain could promote this problem. This abiotic disease is often worse when dry periods are followed by heavy rains.
Cultivars can vary in their susceptibility to rain check. Those tomato cultivars that have good leaf cover to protect tomatoes and good epidermis characteristics seem to be more tolerant of rain check. Glossy fruit tends to have less rain check than dull fruit.
Management: Choose tolerant cultivars and cultural practices that reduce fruit exposure.
Another abiotic problem on tomato fruit (as seen below) is called zippering, which is a thin, brown, necrotic scar, starting at the stem and can extend partly or all the way to blossom end. This long scar has transverse scars across it, which resembles a zipper. Often times, there is only one zipper that forms per fruit, but there could be several zippers.
The cause of zippering is anthers that attach to the ovary wall of the newly forming fruit and seems to be more pronounced in cool weather, but can occur during other weather conditions. Tomato cultivars will vary in their susceptibility.
Management: Grow tolerant cultivars and maintain proper temperatures when growing in a greenhouse.
In conclusion, how can you try to avoid most of the abiotic diseases of tomato fruit:
- Fight with Mother Nature
- Provide even watering (if possible)
- Provide even temperatures (greenhouse)
- More nitrogen or overfertilization can be bad!
- Don't get too crazy with your pruning!
- Control disease and insects
- Overall, maintain good nutrition of tomatoes
- If you continue to have a problem, you may want to consider growing a different tomato cultivar