Cooperative Extension Service 
Institute of Food and Agricultural Sciences
Hendry County Extension P. O. Box 68 LaBelle, Florida 33975-0068 Phone (863) 674-4092

Hendry County Horticulture News

Blossom End Rot - Moisture and Calcium Levels are Key

Dark brown or black blotches on the bottom of tomato fruit are a sure sign of blossom-end rot.  In addition to tomato, blossom-end rot can cause problems in other crops, particularly peppers and melons.  This problem shows up in many home gardens each season, but this year's drought and resultant water stress has made this problem especially severe this spring.  Here are some steps which can be taken in late summer before planting your garden which will help prevent blossom-end rot in the next crop.

Home gardeners sometimes confuse blossom-end rot, since the may mistake the problem with other tomato diseases.  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 or in soils which are alternately wet and dry during fruit development are more likely to show blossom-end rot.  The problem generally is more severe when plants are fertilized too heavily with nitrogen fertilizer.

Begin now to correct past garden problems with blossom-end rot by following these recommendations.  They should help reduce fruit losses to blossom-end rot. Collect a soil sample in the off season (summer is a good time to carry out this project) to determine levels of calcium so that any calcium deficiency problem can be corrected through application of lime.  This should be done before the fall planting season -- if you're not sure about the procedure for collecting soil samples, check with the Hendry County Extension Office for details.

Blossom-end rot is also related to moisture supply, so during the growing season, don't forget to keep a close eye on your plants, monitor soil moisture, and irrigate before signs of moisture stress are apparent.  As a general rule, during the growing season, tomato plants need at least one inch of water per week in the form of rain or supplemental irrigation.  Consider mulching your tomato plants, since this practice will help maintain uniform soil moisture conditions.

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).  Sprays containing calcium chloride will help to prevent further development of the problem but will not cure fruits already affected.  Be sure to follow label directions carefully as it is possible to burn your plants by excess or improperly applied calcium chloride!

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 since excess nitrogen will promote leaf growth and mobilize available calcium away from developing fruits and into rapidly expanding leaves.  Learn from your problems and start to plan now for a better crop next year.  Good luck and good gardening.

Gene McAvoy is the horticulture agent with the Hendry County Extension Service.  Direct your horticulture questions to PO Box 68, LaBelle, FL 33975,  e-mail - or phone 863-674-4092 or 863-983-1598.  You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle.   Office hours are from 8:00 - 5:00.

The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity - Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin.

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