Blossom End Rot Information

Blossom End Rot Information - Pest Control

By Jennifer Olvera, Garden Guides Contributor
Blossom End Rot

About Blossom End Rot

Blossom end rot is a problematic disease that affects both commercially grown and homegrown tomatoes, causing severe crop loss.

Prevention and Control

Prevention of blossom end rot depends on maintaining adequate supplies of moisture and calcium to developing fruit. Tomato plants should neither be too hardened nor too succulent when planted and should be planted in well-drained, aerated, warm soil. Mulching soil helps maintain adequate water supply when moisture is at a premium. In home gardens, shading plants during heat is beneficial.

Use a fertilizer low in nitrogen but high in superphosphate, such as 4-12-4 or 5-20-5, to treat blossom end rot. Foliage can be sprayed with calcium chloride solutions, but extreme caution is required since calcium chloride is phytotoxic if applied too frequently or in excessive amounts.

Affected Plants

The disease does not spread from plant to plant or fruit to fruit. Blossom end rot most often affects tomatoes but also can affect peppers, squash and watermelon.


Symptoms appear on the blossom end of the fruit. Blossom end rot appears as small, water-soaked spots that get bigger and darken quickly as the fruits develop, covering as much as half of the fruit's surface. The spots dry out, becoming flat, black and leather-like in appearance and texture.

Natural Insecticides

Fungicides and insecticides are not helpful in treating and preventing blossom end rot.

Other Methods of Control

Lime soil to pH 6.5 to 6.7, and be sure to fertilize correctly. In home gardens that have not been soil tested, 5 pints of 8-8-8 per 100 feet should be worked into the top 8 inches of soil. Mulch around plants and make sure tomato plants get 1 1/2 inches of water weekly. Plants also can be sprayed with calcium (4 tablespoons per gal of water).

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