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Tomato blossom end rot (calcium disorder) Photo: Tulspal · CC BY-SA 4.0 · source ↗

Tomato blossom end rot (calcium disorder)

Blossom end rot (BER) is a physiological disorder of tomato fruit caused by localised calcium deficiency in the developing fruit tip. It is one of the most common dry-season tomato problems in the Madanapalle, Anantapur and Chittoor cluster, surfacing whenever calcium uptake fails to keep pace with rapid fruit expansion. ICAR-IIVR (Varanasi) and the University of California list BER as a calcium-mediated disorder triggered by water stress, rather than a microbial disease.

Identification and symptoms

The first symptom is a small water-soaked spot at the blossom (distal) end of the developing fruit. The spot enlarges, turns dark brown to black, becomes sunken and leathery, and may cover one-third to half of the fruit. Secondary fungal and bacterial colonisation often follow, but the primary lesion is sterile and dry. Symptoms appear when the fruit is half- to two-thirds-grown and persist on the fruit through ripening. Brinjal, capsicum and watermelon show similar BER symptoms from the same physiological cause.

Cause and conditions

The disorder is not a pathogen; it is caused by inadequate calcium delivery to the fast-expanding cells at the blossom end of the fruit. Calcium is transported in the xylem along with water, so any factor that disrupts water flow causes localised calcium starvation:

  • Irregular irrigation (long dry spells followed by heavy watering).
  • High soil EC or salinity restricting root water uptake.
  • Acid soils with low exchangeable calcium.
  • Excess ammoniacal nitrogen or potassium fertilisation, which compete with calcium uptake.
  • Hot, dry windy conditions that increase transpiration faster than calcium can be re-translocated.
  • Root damage from nematodes or stem rot.

Damage and economic impact

In dryland and rainfed transplanted tomato, BER can affect 10-40 percent of the first two fruit clusters in summer months. The affected fruit is unmarketable, downgraded at the mandi (Madanapalle Tomato Main Yard, Mulakalacheruvu Tomato Market) and contributes to the perception of poor field management. The disorder is most pronounced in indeterminate hybrids on light, low-OM red soils under deficit drip irrigation.

Management

  • Steady soil moisture: keep soil moisture in a narrow range through drip fertigation (Drip Fertigation Vegetables); avoid alternating dry-wet cycles. Mulching (Mulching Vegetables) with paddy straw or plastic stabilises moisture.
  • Calcium supply: at land preparation, apply gypsum at 200-400 kg/acre or lime if soil pH is below 6.0. In fertigation, include calcium nitrate at 2-3 kg per acre per week during fruit development. Avoid bulk SOP/MOP and urea applications during fruit set as they aggravate the deficit.
  • Foliar correction: weekly foliar spray of calcium nitrate (4-5 g/L) or calcium chloride (2-3 g/L) during early fruit set; calcium-magnesium-boron (Calcium Magnesium Foliar) combination formulations are widely used. Foliar calcium reaches only the leaves and is partial; soil and irrigation discipline is the main lever.
  • Resistant varieties: thicker-walled determinate hybrids show lower BER expression; growers report less BER in Sahoo, Salaar and ARYAMAN under summer cropping.

Limitations

Once a fruit shows BER it cannot be cured. Management must be preventive and is most effective if started before symptoms appear in the first cluster. Severe BER in repeated seasons may indicate root damage (nematode, stem rot) rather than calcium supply per se.

See also: Tomato crop, Summer tomato cultivation, Tomato early and late blight, Calcium-magnesium foliar, Mulching vegetables.

Sources

  1. Blossom end rot of tomato. ICAR-Indian Institute of Vegetable Research, Varanasi.
  2. Blossom end rot - tomato management. University of California Agriculture & Natural Resources.