One of the main problems that are found with regard to forced crops is the appearance, during the growth stage, of a physiological disorder known as apical rotting, apical necrosis, peseta or “blossom end rot”.

This damage is caused by localized calcium deficiency in the distal tissues of the fruit.

The crops that tend to present symptoms of “blossom end rot” are tomatoes, peppers, aubergines and melons.

Calcium is involved in maintaining the completeness of cell membranes, given the fact that a deficiency could cause the loss of cell contents and the destruction of tissue structure.

This disorder may be recognised as a black area which is visible in the apical part of the fruit, and in crops which are sensitive, this may cause internal rotting to set in.

The most common cause of blossom end rot is the combination of high temperature and humidity.

"Blossom end" rot can be minimised or avoided by putting the following instructions into practice:

- By growing non-susceptible crops
- By avoiding root temperatures lower than 18º C at the beginning of crop growth
- By ventilating in order to avoid high atmospheric temperatures
- By maintaining an adequate humidity level in the inert hydroponic soil
- By avoiding high salt contents in warm climates
- By maintaining adequate levels of calcium in the soil or via nutritive solution
- By avoiding excessive levels of potassium and magnesium
- By wetting the passages in greenhouses at midday thoroughly; in order to increase humidity levels which decreases transpiration and the transfer of calcium to the leaves; this in turn makes more calcium available for the fruit
- By reducing the levels of carbon dioxide temporarily in order to decrease the growth of both the plant and the fruit
- By treating the plant with a 2% calcium oxide complex solution
- By moving the leaves of the plants, in hot climates, in order to ensure that they get plenty of fresh air