Blossom end rot in San Marzano paste tomatoes

Blossom End Rot

Google Images of Blossom End Rot

Physical Description

Blossom end rot in tomato

Blossom end rot in tomato

Brown or tan spots on the blossom end of tomatoes or on the underside of peppers.

Blossom end rot results from calcium availability problems when the fruit is forming. Calcium availability is affected by irrigation levels (both too much water, and too little water), as well as by the amount of calcium present in the soil.

Plants Affected

  • tomatoes
  • peppers
  • zucchini

Plants Unaffected

Signs & Symptoms

Whole Plant




  • Brown or tan spots on the blossom end of tomatoes
  • Brown or tan spots on the underside of peppers
  • fruit is still edible – just cut off the damaged parts
  • brown and rotting zucchini at the blossom end


How to Positively Identify


  • make sure soil is kept evenly moist (not too wet, not too dry)
  • add calcium
    • crushed oyster shells
    • crushed egg shells
    • calcium supplement for plants

Prevention & Control

Cultural Controls:


Temperature & Humidity:

– irregular water & heat cause blossom end rot by preventing the plant from getting enough calcium from the soil

Mulching & Cultivation Practices:

  • use automated drip or in-line irrigation to keep soil moisture consistent
  • make sure calcium levels are kept up in soil

Natural Enemies & Biological Controls






Sprays & Dusts


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