|May 2008. An experienced vegetable grower in Cook Islands has a new problem on tomatoes. It starts with a small sunken spot (1/2 cm diameter) on the side of the fruit below the pedicel. A few days to a week later, cracks appear in the middle of the sunken spot. It occurs on maturing fruits and is especially serious during rainy periods. The tomato variety is Heatmaster, planted in sandy soil.
It was suggested that the problem was caused by the fruit-piercikng moth, and so searches should be made at night.
Another suggestion was that it was a physiological condition combined with early secondary infection. The sandy soil could be the culprit. It might be worth having a look at irrigation cycles. In sandy soils with lower water retention, shorter and more frequent irrigation would ensure better balance rather than the other way round. Sandy soils with lower CEC may also be prone to mineral deficiencies. A couple of rounds of multi-mineral sprays while waiting for a complete diagnosis can often produce dramatic results.
Finally, there was a suggestion that the spots were caused by Alternaria and Bacterial speck, but early blight (Alternaria solani) and bacterial speck (Pseudomonas syringae) symptoms would have been obvious on leaves as well as fruits. They were unlikely to be the cause.