Blossom-end Rot of Tomatoes

R. Keith Collins  |  7/12/2010 9:11:39 PM

News Article from The Richland Beacon and the The Delhi Dispatch

Keith Collins, County Agent

Dark brown or black blotches on the bottom of tomato fruit is a sure sign of blossom-end rot. This problem shows up in many home vegetable gardens across Richland Parish each season. The first indication of blossom-end rot is a slight discoloration, water-soaked in appearance, occurring at the blossom-end (bottom) of the fruit. This area enlarges rapidly, producing a brown or black sunken area. The skin over the affected area becomes dry and leathery. Blossom-end rot is caused by a shortage of calcium in developing fruit. This may be due to a lack of calcium uptake from the soil or to extreme fluctuations in water supply. Tomato plants growing in soils low in calcium and soils which are alternately wet and dry during fruit development are more likely to show blossom-end rot. Also, this problem generally is more severe when plants are fertilized too heavily with nitrogen fertilizer.

The following are some suggestions that should reduce fruit losses to blossom-end rot:

  • Collect a soil sample in the off-season to determine levels of calcium so that any calcium deficiency problem can be corrected through application of lime.
  • Blossom-end rot is also related to moisture supply, so during the growing season, monitor soil moisture, and irrigate before signs of moisture stress are apparent. As a general rule, tomato plants need at least one inch of water per week in the form of rain or supplemental irrigation.
  • If blossom-end rot should begin to show up, apply several sprays of calcium chloride (available at garden supply stores under a variety of trade names). Follow label directions. Sprays containing calcium chloride will help to prevent further development of the problem but will not cure fruits already affected.
  • Remove fruit showing symptoms of blossom-end rot when the problem is first observed. This practice will reduce the drain of food and nutrient materials which otherwise would be available for development of other fruit not affected by blossom-end rot.
  • It's especially important to follow a recommended program of fertility and avoid excessive application of nitrogen fertilizer.

Contact your local County Extension office for further information at (318) 728-3216.

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