Blossom end rot, or Dry rot, or dry top or is a common problem that occurs on tomatoes, but also on peppers and eggplants.
The appearance of the problem starts with a dark spot 1 to 2 cm in diameter at the bottom of the tomato fruit. The spot is dark in color. At the point where the spot appears, the fruit becomes dented.
The spot gradually increases in size and spreads to cover the entire lower part of the tomato fruit.
Although blossom end rot alone causes only a local problem, the problem gets worse as organisms take advantage of the problem and enter the fruit. The result is rotting of the fruit.
Different varieties of tomatoes have different resistance to the problem
For example, small tomato varieties such as Santorini tomatoes and cherry tomatoes are very resistant and rarely have the problem.
In contrast, varieties that produce regular or large tomatoes are very susceptible to the problem.
Causes of blossom end rot
The most likely causes for the occurrence of the problem are:
- Calcium deficiency – soil with little usable calcium
- Lack of calcium absorption
- Inconsistent watering
- Excessive use of fertilizers containing nitrogen, magnesium and potassium, which work in competition with calcium
- Low soil pH
- Soil that is easily washed away or retains too much water
- Prolonged water deficiency
- Intense heat during the growth phase of the fruit
- Use of unsuitable potting soil combined with irregular watering
- Add calcium to the soil before planting. Calcium can be added in the form of marble dust to be mixed with the soil. The addition of calcium also increases the pH of the soil
- Limiting the use of fertilizers containing potassium, magnesium, nitrogen and ammonia
- Constant irrigation (watering) schedule
- Periodic trans-wave spraying of plants with phosphate fertilizers or calcium nitrate or calcium chloride during the afternoon hours
Tomato diseases and disorders (PDF) by Mark L. Gleason and Brooke A. Edmunds, Department of Plant Pathology
Growing Tomatoes in the Greenhouse, Komnakos Ioannis, Stamoulis Publications
Blossom End Rot, KALLIERGO