The Pro Farmer

Preventing Blossom End Rot in Tomatoes, Peppers, and Watermelons: Causes, Symptoms, and Solutions

Blossom end rot (BER)-

A common garden problem that often occurs on both green and ripe fruits of tomato, pepper and watermelon.

It is characterized as brown, leathery rot developing on or near the blossom end of the fruit.

The reason is lack of Calcium arriving at the fruit.

It is usually thought of as caused by a lack of calcium and/or uneven watering, but it’s not just that.

A shortage of Calcium at the fruits can be caused by several reasons:

Calcium deficiency in the soil

Weak root system

Water shortage

High salinity or high EC levels caused by high evaporation

Long stems in mature plants

Drastic weather, high temperatures, wind, and low humidity.

If you think there is a high chance for BER to occur, you can do these things for prevention:

1) maintain consistent levels of moisture in the soil, but don’t flood the soil.

2) prevent calcium deficiency with the proper fertilizer.

3) Pruning leaves especially the ones at the top will cause Calcium to shift to the fruits

4) Try to encourage more fruits on the plant, this will function as a strong source of Calcium attraction

5. Raise the PH of the soil. Calcium is not available to plants, even if it exists, in soils with PH less than 5 (acidic soil). Places with high precipitation tend to have acidic soil.

6. Nitrogen and Potassium Compete with calcium on absorption by the plant roots, so it will be helpful to fertilize less with these elements when fruits evolve.

7. Potassium encourages Calcium absorption, so adding it to the soil as a fertilizer, at this point will be helpful.

8. Irrigate at night. Calcium is transported to the fruits, better at night when it less hot.

Calcium sometimes finds it difficult to move from the roots to the fruits.

A deficiency of calcium in an embalming flower (after pollination) will cause blossom end rot, a few weeks later in the fruit.

Yes, this is how early calcium deficiency affects BER.

So, lack of irrigation, as early as in the flower stage, can cause blossom end rot, in the fruit later on.

Spraying liquid calcium fertilizer is recommended, if the previously mentioned solutions do not seem to work.

It is recommended to try a foliar spraying of Calcium.

The effect of soil pH on nutrient availability.

The leaves will absorb the calcium immediately, and hopefully will transport it to the “new soon to be fruits”, more efficiently.

Determinate tomato varieties usually only produce one tomato harvest in a season, so spray once or twice a week for 3 weeks.

The first spray should be in the very early crucial stage when the flower becomes a fruit (fruit embalming).

In case you are growing Indeterminate varieties of tomato plants, that can bear fruits more than once, (producing fruit until frost) you should spray every week.

The dosage is around 1 oz of calcium fertilizer per 8 gallons of water (1cc of calcium fertilizer per 10L of water).

If that spraying calcium does not work either, you can try to change the variety you grow to another similar one.

Maybe the variety is too sensitive to the conditions in your soil.

Usually, the San Marzano and Roma tomato types are most affected by Ber, because of their elongated shape that apparently makes calcium difficult to reach the bottom tip.

Calcium (Ca)

Calcium is an important component in the structure of protopectin, an essential sticky substance used as “cement”.
Holding the cells together and creating stability in the cell structure.

It helps to form strong stems and branches and also contributes to the formation of roots.
In addition, calcium helps in the absorption of potassium.

Calcium plays an important role in preventing damage from environmental stresses (heat, cold, wind, UV radiation).

Calcium is an important component in many enzymes that play an important role in the ripening process.

The movement of calcium between the organs of the plant is low.

A shortage of it, even temporary, will immediately stand out in the young growth areas, leaves or fruits, without the ability to “attract” it from older leaves where it can be found in high concentrations.

Calcium uptake and movement in the plant depend on the general water economy.

Therefore, during a water shortage, even temporarily, the supply to the young organs will be impaired and symptoms of deficiency, a spring of necrosis (tissue collapse) will appear at the apex of growth or at the tips of the fruit.

Feeding the plant with calcium is not easy, due to its limitations in availability in different soil conditions and limited mobility in the soil.

The mechanisms of its transport in the plant to the fruit are also problematic.

In some cases, if you know that the soil does have enough calcium, you can try irrigating more frequently, but do not flood.

Irrigate more times with smaller amounts.

It is also recommended to try a foliar spraying of Calcium.

The leaves will absorb the calcium immediately. If nothing works, just change the variety you grow to another similar one.

Maybe it is too sensitive.

Calcium deficiency:

Calcium deficiency basically occurs in all varieties of fruits and especially in the parts of the plant from which there is low transpiration, which means mainly the fruits.

Fruits with calcium deficiency ripen early, there is a discoloration to yellow in the peel of the fruit, the fruit has low acidity and lack of solidity.

In addition, in fruits with calcium deficiency the aging stages of the fruits are faster.

The upper leaves of the plant will take twisted and unusual shapes, white spots will appear on the leaves.

Calcium excess:

Excess calcium will lead to deficiency in other elements, such as magnesium and potassium.

The plant stem will have difficulty holding the plant upright.

If there are no traces of Calcium in the runoff water or in the soil water solution, then adding calcium is advised.

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