by Keith C. Hansen, Extension Horticulturist
Blossom end rot, a common malady on tomatoes, is showing up now that large-fruited tomatoes have set fruit and sizing up. Both green and red fruit develop a black, dry rot area on the bottom or base of the fruit.
This is not a disease but a physiological problem. The following is taken from the Texas A&M Plant Disease Handbook:
Blossom end rot is a physiological disorder of tomato that can appear on fruits at any time in
their development, but most commonly appears when fruits are one-third to one-half grown. The initial symptoms are
water-soaked spots on the blossom end of the fruit. These spots later enlarge and become black. Secondary infection by other
decay causing organisms usually follows. The cause of this disorder is considered to be calcium deficiency in the developing
fruit. Extreme fluctuations in moisture, root pruning and excessive nitrogen fertilization can also result in blossom end rot. Best
means of control is to maintain a uniform supply of moisture through irrigation and soil mulches. Calcium chloride can be used
as a spray for control under some conditions.
For pictures and other descriptions click here for more blossom end rot photos, etc.
Keith Hansen is Smith County Horticulturist with Texas Cooperative Extension. His web page is http://aggie-horticulture.tamu.edu/county/smith. Educational programs of Texas Cooperative Extension are open to all individuals without regard to race, color, sex, disability, religion, age or national origin.
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