Home and Landscape

Blossom End Rot

Blossom end rot affects tomatoes, peppers, and cucurbits. Plants with blossom end rot show small, light brown spots at the blossom end of immature fruit. The affected area gradually expands into a sunken, leathery, brown or black lesion as the fruit ripens. Hard, brown areas may develop inside the fruit, either with or without external symptoms. The disease is not associated with soil contact or with damage to other plant parts.

Solutions

Blossom end rot results from a low level of calcium in the fruit and water balance in the plant. It is aggravated by high soil salt content or low soil moisture and is more common on sandier soils. To reduce rot, monitor soil moisture to make sure that the root zone neither dries out nor remains saturated. Follow recommended rates for fertilizers. Some varieties are more affected than others. The disease is not caused by a pathogen; there are no pesticide solutions.

Blossom end rot fruit (calcium deficiency) showing small brown spot at blossom end, 1/2X; . Credit: Jack Kelly Clark, UC IPM
Start of blossom end rot on tomato fruit. Credit: Jack Kelly Clark, UC IPM
Blossom end rot fruit (calcium deficiency) showing sunken, leathery, brown lesion at blossom end; . Credit: Jack Kelly Clark, UC IPM
Sunken, leathery lesions on tomatoes. Credit: Jack Kelly Clark, UC IPM
Zucchini rotting from blossom end rot, a mineral imbalance disorder.    Credit: Robert D. Raabe
Rotting of zucchini. Credit: Robert D. Raabe
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